Wikipedia:WikiProject Mathematics/MathFormattingBugs

This page lists bugs and inconsistencies with the mathematical formatting system using the math extension with different preferences (server-side SVG/client-side SVG/client-side MathML).

The current default rendering mode, "server-side SVG", has been the default for many years. But a new rendering mode, "client-side SVG", is imminently scheduled to be deployed as the default, at which point "server-side SVG" will be removed as an option. In the long term, developers have a goal of making "client-side MathML" the default rendering mode.

To see every article in English Wikipedia with the new rendering mode, visit Special:Preferences § mw-prefsection-rendering and change the "Math" setting to "MathML with SVG image (client side MathJax rendering)".

To view a specific article with a particular rendering preference, without changing the global preference setting, append ?mathmode=mathml to the URL for "server-side SVG", append ?mathmode=mathjax for "client-side SVG", and append ?mathmode=native for "client-side MathML".

Yes, these names are confusing:

"Server-side SVG" (mathml, current default mode) means that the original LaTeX mathematics markup is converted to an SVG image on the server side using the MathJax library, version 2. This SVG image is sent directly to the reader's browser for display.
"Client-side SVG" (mathjax, planned new default) means that the LaTeX markup is converted to MathML on the server side using a brand new PHP library unique to mediawiki, sent in MathML format to the browser, and then converted to an SVG image using the MathJax library, version 4, running directly in the reader's browser (note that MathJax is intended to be used to ingest the original LaTeX markup, so this is non-standard use of MathJax).
"Client-side MathML" (native) means that the LaTeX markup is converted to MathML on the server side using the same PHP library, and then that MathML code is directly rendered by the reader's browser.

See Help:Displaying a formula for more general information about including mathematics within English Wikipedia articles. See #Formatting notes, below, for how to add entries.

Problems with client-side SVG mode

Math format inconsistencies
Number	LaTeX markup	Server-side SVG	Client-side SVG	Client-side MathML	Notes
T437135 mathml, T437135 svg	`\begin{align} & A \mathord{\vert} B \\ & A \mathop{\vert} B \\ & A \mathbin{\vert} B \\ & A \mathrel{\vert} B \\ & A + \mathopen{\vert} B \\ & A \mathclose{\vert} + B \\ & A \mathpunct{\vert}B \end{align}`	${\begin{aligned}&A{\mathord {\vert }}B\\&A\mathop {\vert } B\\&A\mathbin {\vert } B\\&A\mathrel {\vert } B\\&A+{\mathopen {\vert }}B\\&A{\mathclose {\vert }}+B\\&A{\mathpunct {\vert }}B\end{aligned}}$	$\begin{matrix} A \| B \\ A \| B \\ A \| B \\ A \| B \\ A + \| B \\ A \| + B \\ A \| B \end{matrix}$	$\begin{matrix} A \| B \\ A \| B \\ A \| B \\ A \| B \\ A + \| B \\ A \| + B \\ A \| B \end{matrix}$	Basic commands to assign roles to symbols or groups of symbols by function so that spacing will be adjusted appropriately do not work properly
	`\begin{align} & 1.2 && 1,234 \\ & 1\mathord{.}2 && 1\mathord{,}234 \\ & 1\mathpunct{.}2 && 1\mathpunct{,}234 \end{align}`	${\begin{aligned}&1.2&&1,234\\&1{\mathord {.}}2&&1{\mathord {,}}234\\&1{\mathpunct {.}}2&&1{\mathpunct {,}}234\end{aligned}}$	$\begin{matrix} 1.2 & 1, 234 \\ 1.2 & 1, 234 \\ 1.2 & 1, 234 \end{matrix}$	$\begin{matrix} 1.2 & 1, 234 \\ 1.2 & 1, 234 \\ 1.2 & 1, 234 \end{matrix}$	`\mathpunct` is incorrectly implemented in all of the rendering modes: it should indicate "punctuation" and add some space after, matching the behavior after e.g. a comma or semicolon.
T437135 mathml, T437135 svg	`\begin{align} & {]}{ A\mathbin{()}B }{[} && {]}{ A+B }{[} \\ & {]}{ {}\mathbin{()}B }{[} && {]}{ {}+B }{[} \\ & {]}{A\mathbin{()}{} }{[} && {]}{A+{} }{[} \\ & {]}{ \mathbin{()}B }{[} && {]}{ +B }{[} \end{align}`	${\begin{aligned}&{]}{A\mathbin {()} B}{[}&&{]}{A+B}{[}\\&{]}{{}\mathbin {()} B}{[}&&{]}{{}+B}{[}\\&{]}{A\mathbin {()} {}}{[}&&{]}{A+{}}{[}\\&{]}{\mathbin {()} B}{[}&&{]}{+B}{[}\end{aligned}}$	$\begin{matrix} ] A () B [ & ] A + B [ \\ ] () B [ & ] + B [ \\ ] A () [ & ] A + [ \\ ] () B [ & ] + B [ \end{matrix}$	$\begin{matrix} ] A () B [ & ] A + B [ \\ ] () B [ & ] + B [ \\ ] A () [ & ] A + [ \\ ] () B [ & ] + B [ \end{matrix}$	`\mathbin` has incorrect spacing when an empty `{}` is used on one side, whether it's a custom binary operation or a built-in like plus.
9 open	`\tbinom{n}{k} \binom{n}{k} {n \choose k}`	${\tbinom {n}{k}}{\binom {n}{k}}{n \choose k}$	$(\binom{n}{k}) (\binom{n}{k}) (\binom{n}{k})$	$(\binom{n}{k}) (\binom{n}{k}) (\binom{n}{k})$	Text style binomial coefficient \tbinom uses too much spacing around the parens
	`\textstyle \tbinom{n}{k} \binom{n}{k} {n \choose k}`	$\textstyle {\tbinom {n}{k}}{\binom {n}{k}}{n \choose k}$	$(\binom{n}{k}) (\binom{n}{k}) (\binom{n}{k})$	$(\binom{n}{k}) (\binom{n}{k}) (\binom{n}{k})$	After setting text style, these three ways of formatting binomial coefficients should be identical, but the (obsolete but still-used) \choose formatting produces too-large parentheses with too much spacing Update: `\choose` seems improved, but `\tbinom` still renders differently from `\binom` when text style is set, and all three types still have too much space inside the parentheses
	`\binom{n}{\frac n2}`	${\binom {n}{\frac {n}{2}}}$	$(\binom{n}{\frac{n}{2}})$	$(\binom{n}{\frac{n}{2}})$	Too much horizontal whitespace around the parentheses in this binomial coefficient with a fraction inside
T435385 (?)	`\Gamma \mathbf{\Gamma}, \Delta \mathbf{\Delta}, \Theta \mathbf{\Theta}`	$\Gamma \mathbf {\Gamma } ,\Delta \mathbf {\Delta } ,\Theta \mathbf {\Theta }$	$Γ 𝜞, Δ 𝜟, Θ 𝜣$	$Γ 𝜞, Δ 𝜟, Θ 𝜣$	bold capital Greek letters render as italic when they aren't supposed to
1b open T435385	`\varDelta \varTheta \varUpsilon \boldsymbol{\Alpha \Beta \Gamma}`	$\varDelta \varTheta \varUpsilon {\boldsymbol {\mathrm {A} \mathrm {B} \Gamma }}$	$𝞓 𝜣 𝜰 𝑨 𝑩 𝜞$	$𝞓 𝜣 𝜰 𝑨 𝑩 𝜞$	full set of typefaces with some glitches to investigate. See mw:Extension:Math/T434428 for full set of typefaces.
2 open	`x\pm y`	$x\pm y$	$x \pm y$	$x \pm y$	`\pm` has the wrong vertical position (the minus part is below the baseline) – perhaps uses the wrong font
	`x \circ y,\, 30^\circ`	$x\circ y,\,30^{\circ }$	$x \circ y, 3 0^{\circ}$	$x \circ y, 3 0^{\circ}$	`\circ` is too small
3 open	`1 \backslash 2 / 3`	$1\backslash 2/3$	$1 ∖ 2 / 3$	$1 ∖ 2 / 3$	`\backslash` is the wrong shape and size, doesn't match `/` – again, perhaps the wrong font
	`\backprime, \prime, X^\backprime, X^\prime`	$\backprime ,\prime ,X^{\backprime },X^{\prime }$	$‵,', X^{‵}, X^{'}$	$‵,', X^{‵}, X^{'}$	`\backprime` and `\prime` are the wrong size and don't match each-other
4 (maybe T417248?)	`x'`	$x'$	$x^{'}$	$x^{'}$	prime is horizontally too far from the letter in client-side SVG mode
4 (maybe T417248?)	`\psi_n''(x)`	$\psi _{n}''(x)$	${ψ_{n}}^{″} (x)$	${ψ_{n}}^{″} (x)$	prime is horizontally much, much too far from the letter after a subscript
5 T434607 new task	`\ddot {x}`	${\ddot {x}}$	$\ddot{x}$	$\ddot{x}$	derivative dots in ⁠ $\ddot{x}$ ⁠ are too small, hard to read
6 open	`\overbrace{ 1+2+\cdots+100 }^{5050}`	$\overbrace {1+2+\cdots +100} ^{5050}$	$\overset{5050}{\overset{⏞}{1 + 2 + \dots + 100}}$	$\overset{5050}{\overset{⏞}{1 + 2 + \dots + 100}}$	spacing around + signs with an overbrace is completely wrong,
	`\textstyle \sqrt{\sum_{k=1}^N k^2 }`	$\textstyle {\sqrt {\sum _{k=1}^{N}k^{2}}}$	$\sqrt{\sum_{k = 1}^{N} k^{2}}$	$\sqrt{\sum_{k = 1}^{N} k^{2}}$	Sum in a square root with text style set uses the wrong format (should be inline style)
	`H_n\left(\frac{\sum_{k=1}^r a_k x_k}{\sqrt{\sum_{k=1}^r a_k^2} }\right)`	$H_{n}\left({\frac {\sum _{k=1}^{r}a_{k}x_{k}}{\sqrt {\sum _{k=1}^{r}a_{k}^{2}}}}\right)$	$H_{n} (\frac{\sum_{k = 1}^{r} a_{k} x_{k}}{\sqrt{\sum_{k = 1}^{r} a_{k}^{2}}})$	$H_{n} (\frac{\sum_{k = 1}^{r} a_{k} x_{k}}{\sqrt{\sum_{k = 1}^{r} a_{k}^{2}}})$	Also affects a sum in a square root in a fraction (Example taken from Hermite polynomials)
8 open	`\int_{a}^{b} x \ dx`	$\int _{a}^{b}x\ dx$	$\int_{a}^{b} x d x$	$\int_{a}^{b} x d x$	Lower limits of integrals are too far from the integral sign
	`\mathcal{T}_{\xi=x_i}^{r_i}`	${\mathcal {T}}_{\xi =x_{i}}^{r_{i}}$	$𝒯_{ξ = x_{i}}^{r_{i}}$	$𝒯_{ξ = x_{i}}^{r_{i}}$	Subscript is too far to the right
17 open	`\tfrac12,\, \tfrac{123}{456},\, \tfrac{a}{b},\, \tfrac{\sqrt2 x}{5y}`	${\tfrac {1}{2}},\,{\tfrac {123}{456}},\,{\tfrac {a}{b}},\,{\tfrac {{\sqrt {2}}x}{5y}}$	$\frac{1}{2}, \frac{123}{456}, \frac{a}{b}, \frac{\sqrt{2} x}{5 y}$	$\frac{1}{2}, \frac{123}{456}, \frac{a}{b}, \frac{\sqrt{2} x}{5 y}$	Text-style fractions have vertical spacing that is much too tight
17 open	`\Bigl(\tfrac{1}{1 + e^2},\, \tfrac{e^2}{1 + e^2}\Bigr)`	${\Bigl (}{\tfrac {1}{1+e^{2}}},\,{\tfrac {e^{2}}{1+e^{2}}}{\Bigr )}$	$(\frac{1}{1 + e^{2}}, \frac{e^{2}}{1 + e^{2}})$	$(\frac{1}{1 + e^{2}}, \frac{e^{2}}{1 + e^{2}})$	Another example of the previous issue: spacing of text-style fractions
	`\\|x\\|`	$\\|x\\|$	$‖ x ‖$	$‖ x ‖$	Poor font used for norm: The two vertical lines are too close together, which compromises legibility.
	`\tfrac{x^{\\|t\\|} }{2}`	${\tfrac {x^{\\|t\\|}}{2}}$	$\frac{x^{‖ t ‖}}{2}$	$\frac{x^{‖ t ‖}}{2}$	This is especially bad at smaller sizes, where the norm symbol is almost completely illegible
	`\left\Vert \vphantom{ \frac{\big)}{\big)} } \Biggl\Vert \biggl\Vert \Bigl\Vert \bigl\Vert \Vert \right.`	$\left\Vert {\vphantom {\frac {\big )}{\big )}}}{\Biggl \Vert }{\biggl \Vert }{\Bigl \Vert }{\bigl \Vert }\Vert \right.$	$‖ ‖ ‖ ‖ ‖ ‖$	$‖ ‖ ‖ ‖ ‖ ‖$	Norm line spacing doesn't match between different sizes of fences
	`\bigl( () \bigr)`	${\bigl (}(){\bigr )}$	$(())$	$(())$	Manually sized `\big` parens are too big. Apparently uses the wrong font
	`{\sin}\bigl(\tfrac14\pi\bigr)`	${\sin }{\bigl (}{\tfrac {1}{4}}\pi {\bigr )}$	$\sin (\frac{1}{4} π)$	$\sin (\frac{1}{4} π)$	Too much horizontal whitespace inside big parens
	`\mbox{if}\ n\ \mbox{is even}`	${\mbox{if}}\ n\ {\mbox{is even}}$	$if n is even$	$if n is even$	Too much space between \mbox and mathematical symbol. The space in the \mbox also looks a bit big.
15 open	<math>f(x) = {}</math><math>x^2</math>	$f(x)={}$ $x^{2}$	$f (x) =$ $x^{2}$	$f (x) =$ $x^{2}$	There's not enough space after the equals sign in `f(x) = {}` which means that a long inline equation broken up into multiple math tags to allow line breaks will have incorrect space between parts.
	let <math>f(x) = {}</math><math>x^2</math>	let $f(x)={}$ $x^{2}$	let $f (x) =$ $x^{2}$	let $f (x) =$ $x^{2}$	Two `<math>` tags in a row have inconsistent baselines and neither one matches the adjacent text baseline. Bizarrely, the inconsistency is different than without the text (see preceding example).
	`C'^{*\!}, C'`	$C'^{*\!},C'$	$C'^{*}, C^{'}$	$C'^{*}, C^{'}$	Inexplicably inconsistent prime symbols
T434504 (this tracker issue currently doesn't address this bug)	`\overline{\operatorname{gd} z},\, \operatorname{gd} z`	${\overline {\operatorname {gd} z}},\,\operatorname {gd} z$	$\overline{gd z}, gd z$	$\overline{gd z}, gd z$	Not enough space between function and argument under overline: The spacing should be the same with or without the overline.
	`\sqrt{t} \sqrt{x \vphantom{t} }`	${\sqrt {t}}{\sqrt {x{\vphantom {t}}}}$	$\sqrt{t} \sqrt{x}$	$\sqrt{t} \sqrt{x}$	Square root symbol is too high, which is especially ugly when trying to equalize the position of multiple square roots
	`\textstyle {F_n}^{\!2}`	$\textstyle {F_{n}}^{\!2}$	${F_{n}}^{2}$	${F_{n}}^{2}$	Superscript too far away, even after negative space
	`\begin{align} &\Q\bigl(\sqrt5\bigr) \\ &\Q\bigl(\sqrt5~\!\bigr) \end{align}`	${\begin{aligned}&\mathbb {Q} {\bigl (}{\sqrt {5}}{\bigr )}\\&\mathbb {Q} {\bigl (}{\sqrt {5}}~\!{\bigr )}\end{aligned}}$	$\begin{matrix} ℚ (\sqrt{5}) \\ ℚ (\sqrt{5}) \end{matrix}$	$\begin{matrix} ℚ (\sqrt{5}) \\ ℚ (\sqrt{5}) \end{matrix}$	Workaround to add a tiny amount of space (`~\!`, + a medium space − a thin space should be something like 4 − 3 = +1 math units) ends up adding absurd amounts of extra space. Update: a lot better now than before, but still a bit wider than the previous spacing.
	`\begin{align} &\sqrt{x} \big/ \sqrt{y} \\ &\sqrt{x} \big/ ~\!\!\sqrt{y} \\ &\sqrt{x} \big/ \!\sqrt{y} \end{align}`	${\begin{aligned}&{\sqrt {x}}{\big /}{\sqrt {y}}\\&{\sqrt {x}}{\big /}~\!\!{\sqrt {y}}\\&{\sqrt {x}}{\big /}\!{\sqrt {y}}\end{aligned}}$	$\begin{matrix} \sqrt{x} / \sqrt{y} \\ \sqrt{x} / \sqrt{y} \\ \sqrt{x} / \sqrt{y} \end{matrix}$	$\begin{matrix} \sqrt{x} / \sqrt{y} \\ \sqrt{x} / \sqrt{y} \\ \sqrt{x} / \sqrt{y} \end{matrix}$	Workaround to remove a tiny amount of space (`~\!\!`, + a medium space − 2 thin spaces) ends up adding extra space instead (in this particular example just `\!` is better, but in some cases that takes out too much whitespace)
	`\begin{align} &xy \\ &x\,y \\ &x~y \\ &x\;y \\ &x\ y \end{align}`	${\begin{aligned}&xy\\&x\,y\\&x~y\\&x\;y\\&x\ y\end{aligned}}$	$\begin{matrix} x y \\ x y \\ x y \\ x y \\ x y \end{matrix}$	$\begin{matrix} x y \\ x y \\ x y \\ x y \\ x y \end{matrix}$	`~` space is far too big. Supposed to be a 'medium' space (3 or 4 math units, equivalent to `\:` in LaTeX, which Mediawiki math mode doesn't support).
T434504 (this tracker issue currently doesn't address this bug)	`\overline\alpha`	${\overline {\alpha }}$	$\overline{α}$	$\overline{α}$	Overline too close to the letter, and not properly horizontally aligned (overline is too far to the right)
	`\overline a`	${\overline {a}}$	$\overline{a}$	$\overline{a}$	Overline is too close to the letter and not wide enough
	`a \equiv b \pmod{m}`	$a\equiv b{\pmod {m}}$	$a \equiv b (\mod m)$	$a \equiv b (\mod m)$	`\pmod` makes too little space before parentheses
	`x ^ {x ^ {568 + xyz + il\ell e c + \rho p} }`	$x^{x^{568+xyz+il\ell ec+\rho p}}$	$x^{x^{568 + x y z + i l ℓ e c + ρ p}}$	$x^{x^{568 + x y z + i l ℓ e c + ρ p}}$	Super-superscript font is illegibly small and thin in "Client-side SVG" mode. Even the superscript font is pretty hard to read for readers with excellent displays and eyesight. (We don't currently seem to do it in any mode, but ideally we'd use a dedicated superscript font with increased weight and slightly changed letter shapes; see optical size. Computer Modern, implemented with Metafont, was designed such that TeX documents made with it would have slightly different letter shapes for every common text size, not just one shape for each symbol scaled up or down.)
	`e^{-\frac{ust}2}\, e^{isx+ity - \frac{s^2}4 - \frac{t^2}4}`	$e^{-{\frac {ust}{2}}}\,e^{isx+ity-{\frac {s^{2}}{4}}-{\frac {t^{2}}{4}}}$	$e^{- \frac{u s t}{2}} e^{i s x + i t y - \frac{s^{2}}{4} - \frac{t^{2}}{4}}$	$e^{- \frac{u s t}{2}} e^{i s x + i t y - \frac{s^{2}}{4} - \frac{t^{2}}{4}}$	Another example of illegibly small superscripts, this time fractions in superscripts. There are 2 issues which both contribute to the problem: first the letters are too thin, and second the fraction doesn't have enough vertical whitespace between letters and fraction bar. Example taken from Hermite polynomials.
	`\sum_0^{\frac12 X }`	$\sum _{0}^{{\frac {1}{2}}X}$	$\sum_{0}^{\frac{1}{2} X}$	$\sum_{0}^{\frac{1}{2} X}$	Vertical fraction in a summation limit is illegibly small
	`(kx)^2,\, \sqrt{ (kx)^2,\, \left(kx\right)^2}`	$(kx)^{2},\,{\sqrt {(kx)^{2},\,\left(kx\right)^{2}}}$	$(k x)^{2}, \sqrt{(k x)^{2}, {(k x)}^{2}}$	$(k x)^{2}, \sqrt{(k x)^{2}, {(k x)}^{2}}$	Superscript after `)` symbol has wrong vertical position (too low) inside a square root, and the position is substantially inconsistent between `)` vs. `\right)`. Update: this seems to be an example where the "server-side SVG" mode doesn't match the behavior of ordinary LaTeX. As a workaround (also applies to LaTeX), can wrap the whole parenthetical in braces and put the superscript after it. Many articles probably expect on the current behavior though.
	`\square ABCD,\, \triangle ABC`	$\square ABCD,\,\triangle ABC$	$◻ A B C D, △ A B C$	$◻ A B C D, △ A B C$	Square symbol is too small, doesn't match size of letters or triangle symbol
9 open	`\bigl[ \begin{smallmatrix} 1 & 1 \\ 1 & 0 \end{smallmatrix} \bigr]`	${\bigl [}{\begin{smallmatrix}1&1\\1&0\end{smallmatrix}}{\bigr ]}$	$[\begin{matrix} 1 & 1 \\ 1 & 0 \end{matrix}]$	$[\begin{matrix} 1 & 1 \\ 1 & 0 \end{matrix}]$	Small matrix is ugly with poor spacing and alignment: concretely, it needs more vertical space between rows, more horizontal space before/after the brackets, and possibly also slightly more horizontal space between columns,
	`\left(\frac{1+x}{2}\right),\, \left(\frac{1+x}{2}\right)^n`	$\left({\frac {1+x}{2}}\right),\,\left({\frac {1+x}{2}}\right)^{n}$	$(\frac{1 + x}{2}), {(\frac{1 + x}{2})}^{n}$	$(\frac{1 + x}{2}), {(\frac{1 + x}{2})}^{n}$	Inclusion of a superscript outside of parentheses breaks the spacing around + sign in a fraction
	`\frac{(x+y)^2}{2},\ \frac{ \left(x+y\right)^2}{2}`	${\frac {(x+y)^{2}}{2}},\ {\frac {\left(x+y\right)^{2}}{2}}$	$\frac{(x + y)^{2}}{2}, \frac{{(x + y)}^{2}}{2}$	$\frac{(x + y)^{2}}{2}, \frac{{(x + y)}^{2}}{2}$	Another similar superscript + fraction combination with this spacing bug
	`\left\vert \frac34 \cdot \frac13 \right\vert,\ \left\vert \frac34 \cdot \frac13 \right\vert^2`	$\left\vert {\frac {3}{4}}\cdot {\frac {1}{3}}\right\vert ,\ \left\vert {\frac {3}{4}}\cdot {\frac {1}{3}}\right\vert ^{2}$	$\| \frac{3}{4} \cdot \frac{1}{3} \|, {\| \frac{3}{4} \cdot \frac{1}{3} \|}^{2}$	$\| \frac{3}{4} \cdot \frac{1}{3} \|, {\| \frac{3}{4} \cdot \frac{1}{3} \|}^{2}$	Another example where the horizontal whitespace is improperly removed
T436876	`\begin{align} \underline{ }\underline{ }\underline{ }\\[1mu] \text{mu} \end{align}`	${\begin{aligned}{\underline {}}{\underline {}}{\underline {}}\\[1mu]{\text{mu}}\end{aligned}}$	$\begin{matrix} \underline{} \underline{} \underline{} \\ mu \end{matrix}$	$\begin{matrix} \underline{} \underline{} \underline{} \\ mu \end{matrix}$	Empty underline ~~renders yellow-red SVG error message "munder"~~ fails to render at all. This matches the behavior from LaTeX but is inconsistent with the behavior from "server-side SVG" mode.
	`\subseteqq,\, \nsubseteqq`	$\subseteqq ,\,\nsubseteqq$	$⫅, ⊈$	$⫅, ⊈$	`\subseteqq` and `\nsubseteqq` are not consistent
	`\bigstar`	$\bigstar$	$★$	$★$	`\bigstar` is too small and thin
	`\longleftrightarrow`	$\longleftrightarrow$	$⟷$	$⟷$	`\longleftrightarrow` is not long
	`\curvearrowleft,\, \circlearrowleft`	$\curvearrowleft ,\,\circlearrowleft$	$↶, ↺$	$↶, ↺$	`\curvearrowleft` and `\circlearrowleft` (and right analogs) are ugly
	`A \leftrightarrows B`	$A\leftrightarrows B$	$A ⇆ B$	$A ⇆ B$	`\leftrigharrows` look bad (too close together, heads too big and not visually vertically aligned)
	`\diagup,\, \diagdown`	$\diagup ,\,\diagdown$	$╱, ╲$	$╱, ╲$	`\diagup` and `\diagdown` use the wrong symbols
	`s_j s_i`	$s_{j}s_{i}$	$s_{j} s_{i}$	$s_{j} s_{i}$	Not enough spacing/kerning after the first subscript makes it look closer to the second s than to the first s
	`\check{a} \check{m}`	${\check {a}}{\check {m}}$	$\overset{ˇ}{a} \overset{ˇ}{m}$	$\overset{ˇ}{a} \overset{ˇ}{m}$	Check symbol (reverse hat) is inconsistent; it is sometimes too big
	`\check{\hat{a} }`	${\check {\hat {a}}}$	$\overset{ˇ}{\hat{a}}$	$\overset{ˇ}{\hat{a}}$	`\check` and `\hat` are not the same size
	`\tilde{a} \tilde{m}`	${\tilde {a}}{\tilde {m}}$	$\tilde{a} \tilde{m}$	$\tilde{a} \tilde{m}$	Sizing of tilde is inconsistent: it is sometimes too big
	`0.{\underbrace{999\ldots}_H}`	$0.{\underbrace {999\ldots } _{H}}$	$0. \underset{H}{\underset{⏟}{999 \dots}}$	$0. \underset{H}{\underset{⏟}{999 \dots}}$	Extra space added to the left of material enclosed by an underbrace
	`\bigoplus_{j=1}^{N} \bigwedge_{k=1}^{j} \prod_{\ell=1}^{k} x_{jk\ell}`	$\bigoplus _{j=1}^{N}\bigwedge _{k=1}^{j}\prod _{\ell =1}^{k}x_{jk\ell }$	$⨁_{j = 1}^{N} ⋀_{k = 1}^{j} \prod_{ℓ = 1}^{k} x_{j k ℓ}$	$⨁_{j = 1}^{N} ⋀_{k = 1}^{j} \prod_{ℓ = 1}^{k} x_{j k ℓ}$	`\bigvee`, `\bigwedge`, `\bigoplus`, `\bigotimes`, and `\bigodot` aren't bold enough for their intended purpose; they should match the visual weight of `\sum` and `\prod`
	`2\mathbf{2}`	$2\mathbf {2}$	$2 𝟐$	$2 𝟐$	mathbf is not heavy enough to easily distinguish bold from non-bold numerals
	\begin{align} & {\color{blue}\blacksquare\ \textbf{blue} } \\ & {\color{red}\blacksquare\ \textbf{red} } \\ & {\color{green}\blacksquare\ \textbf{green} } \\ & {\color{cyan}\blacksquare\ \textbf{cyan} } \\ & {\color{magenta}\blacksquare\ \textbf{magenta} } \\ & {\color{yellow}\blacksquare\ \textbf{yellow} } \\ & {\color{brown}\blacksquare\ \textbf{brown} } \\ & {\color{lime}\blacksquare\ \textbf{lime} } \\ & {\color{olive}\blacksquare\ \textbf{olive} } \\ & {\color{orange}\blacksquare\ \textbf{orange} } \\ & {\color{pink}\blacksquare\ \textbf{pink} } \\ & {\color{purple}\blacksquare\ \textbf{purple} } \\ & {\color{teal}\blacksquare\ \textbf{teal} } \\ & {\color{violet}\blacksquare\ \textbf{violet} } \\ & {\color{black}\blacksquare\ \textbf{black} } \\ & {\color{gray}\blacksquare\ \textbf{gray} } \\ & {\color{darkgray}\blacksquare\ \textbf{darkgray} } \\ & {\color{lightgray}\blacksquare\ \textbf{lightgray} } \\ & {\color{white}\blacksquare\ \textbf{white} } \\ \end{align}	${\begin{aligned}&{\color {blue}\blacksquare \ {\textbf {blue}}}\\&{\color {red}\blacksquare \ {\textbf {red}}}\\&{\color {green}\blacksquare \ {\textbf {green}}}\\&{\color {cyan}\blacksquare \ {\textbf {cyan}}}\\&{\color {magenta}\blacksquare \ {\textbf {magenta}}}\\&{\color {yellow}\blacksquare \ {\textbf {yellow}}}\\&{\color {brown}\blacksquare \ {\textbf {brown}}}\\&{\color {lime}\blacksquare \ {\textbf {lime}}}\\&{\color {olive}\blacksquare \ {\textbf {olive}}}\\&{\color {orange}\blacksquare \ {\textbf {orange}}}\\&{\color {pink}\blacksquare \ {\textbf {pink}}}\\&{\color {purple}\blacksquare \ {\textbf {purple}}}\\&{\color {teal}\blacksquare \ {\textbf {teal}}}\\&{\color {violet}\blacksquare \ {\textbf {violet}}}\\&{\color {black}\blacksquare \ {\textbf {black}}}\\&{\color {gray}\blacksquare \ {\textbf {gray}}}\\&{\color {darkgray}\blacksquare \ {\textbf {darkgray}}}\\&{\color {lightgray}\blacksquare \ {\textbf {lightgray}}}\\&{\color {white}\blacksquare \ {\textbf {white}}}\\\end{aligned}}$	$\begin{matrix} ◼ 𝐛𝐥𝐮𝐞 \\ ◼ 𝐫𝐞𝐝 \\ ◼ 𝐠𝐫𝐞𝐞𝐧 \\ ◼ 𝐜𝐲𝐚𝐧 \\ ◼ 𝐦𝐚𝐠𝐞𝐧𝐭𝐚 \\ ◼ 𝐲𝐞𝐥𝐥𝐨𝐰 \\ ◼ 𝐛𝐫𝐨𝐰𝐧 \\ ◼ 𝐥𝐢𝐦𝐞 \\ ◼ 𝐨𝐥𝐢𝐯𝐞 \\ ◼ 𝐨𝐫𝐚𝐧𝐠𝐞 \\ ◼ 𝐩𝐢𝐧𝐤 \\ ◼ 𝐩𝐮𝐫𝐩𝐥𝐞 \\ ◼ 𝐭𝐞𝐚𝐥 \\ ◼ 𝐯𝐢𝐨𝐥𝐞𝐭 \\ ◼ 𝐛𝐥𝐚𝐜𝐤 \\ ◼ 𝐠𝐫𝐚𝐲 \\ ◼ 𝐝𝐚𝐫𝐤𝐠𝐫𝐚𝐲 \\ ◼ 𝐥𝐢𝐠𝐡𝐭𝐠𝐫𝐚𝐲 \\ ◼ 𝐰𝐡𝐢𝐭𝐞 \end{matrix}$	$\begin{matrix} ◼ 𝐛𝐥𝐮𝐞 \\ ◼ 𝐫𝐞𝐝 \\ ◼ 𝐠𝐫𝐞𝐞𝐧 \\ ◼ 𝐜𝐲𝐚𝐧 \\ ◼ 𝐦𝐚𝐠𝐞𝐧𝐭𝐚 \\ ◼ 𝐲𝐞𝐥𝐥𝐨𝐰 \\ ◼ 𝐛𝐫𝐨𝐰𝐧 \\ ◼ 𝐥𝐢𝐦𝐞 \\ ◼ 𝐨𝐥𝐢𝐯𝐞 \\ ◼ 𝐨𝐫𝐚𝐧𝐠𝐞 \\ ◼ 𝐩𝐢𝐧𝐤 \\ ◼ 𝐩𝐮𝐫𝐩𝐥𝐞 \\ ◼ 𝐭𝐞𝐚𝐥 \\ ◼ 𝐯𝐢𝐨𝐥𝐞𝐭 \\ ◼ 𝐛𝐥𝐚𝐜𝐤 \\ ◼ 𝐠𝐫𝐚𝐲 \\ ◼ 𝐝𝐚𝐫𝐤𝐠𝐫𝐚𝐲 \\ ◼ 𝐥𝐢𝐠𝐡𝐭𝐠𝐫𝐚𝐲 \\ ◼ 𝐰𝐡𝐢𝐭𝐞 \end{matrix}$	Lowercase color names do not result in the expected colors. (We don't document the lower-case color names, it would be better if people didn't use them, and we should perhaps convert them all to upper-case alternatives site-wide, with human checking, but the lower-case versions should probably not behave differently in different modes, and any switch might affect some pages.)
T442755?	`\operatorname{fi{.}fl{.}ffl}`	$\operatorname {fi{.}fl{.}ffl}$	$f i . f l . f f l$	$f i . f l . f f l$	Native TeX uses ligatures but none of the Wikipedia rendering modes do.
	`\mathcal{ABC}`	${\mathcal {ABC}}$	$𝒜 ℬ 𝒞$	$𝒜 ℬ 𝒞$	The font used for `\mathcal` has changed, and doesn't necessarily match author intent.

Larger equations
Number	LaTeX markup	Server-side SVG	Client-side SVG	Client-side MathML	Notes
	`\begin{array}{llllll} \begin{align}X \\ Y \\[30pt] {} \end{align} & \begin{align}X \\[30pt] Y \\ {} \end{align} & \begin{align}X \\[30px] Y \\ {} \end{align} & \begin{align}X \\[3em] Y \\ {} \end{align} & \begin{align}X \\[.417in] Y \\ {} \end{align} & \begin{align}X \\[54mu] Y \\ {} \end{align} \end{array}`	${\begin{array}{llllll}{\begin{aligned}X\\Y\\[30pt]{}\end{aligned}}&{\begin{aligned}X\\[30pt]Y\\{}\end{aligned}}&{\begin{aligned}X\\[30px]Y\\{}\end{aligned}}&{\begin{aligned}X\\[3em]Y\\{}\end{aligned}}&{\begin{aligned}X\\[.417in]Y\\{}\end{aligned}}&{\begin{aligned}X\\[54mu]Y\\{}\end{aligned}}\end{array}}$	$\begin{matrix} \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} \end{matrix}$	$\begin{matrix} \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} & \begin{matrix} X \\ Y \end{matrix} \end{matrix}$	Manually adjusted vertical spacing has changed in a way that will break many, many articles. This needs to match server-side SVG mode.
	{{box\|<math>\begin{align} x &= 1, \\ y &= 2.\end{align}</math>}} {{box\|<math>\begin{align} x &= 1, \\ y &= 2. \\ {} \end{align}</math>}}	${\begin{aligned}x&=1,\\y&=2.\end{aligned}}$ ${\begin{aligned}x&=1,\\y&=2.\\{}\end{aligned}}$	$\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$ $\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$	$\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$ $\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$	A trailing line with an explicit `{}` on it at the end of the `align` environment is improperly ignored.
10 open	`\begin{bmatrix} 0 & \cdots & 0 \\ \vdots & \ddots & \vdots \\ 0 & \cdots & 0 \end{bmatrix}`	${\begin{bmatrix}0&\cdots &0\\\vdots &\ddots &\vdots \\0&\cdots &0\end{bmatrix}}$	$[\begin{matrix} 0 & \dots & 0 \\ ⋮ & ⋱ & ⋮ \\ 0 & \dots & 0 \end{matrix}]$	$[\begin{matrix} 0 & \dots & 0 \\ ⋮ & ⋱ & ⋮ \\ 0 & \dots & 0 \end{matrix}]$	all types of ellipsis use the wrong font – the dots are spaced much too closely together
11 open	`\begin{bmatrix} x & y \\ z & v \end{bmatrix}`	${\begin{bmatrix}x&y\\z&v\end{bmatrix}}$	$[\begin{matrix} x & y \\ z & v \end{matrix}]$	$[\begin{matrix} x & y \\ z & v \end{matrix}]$	There's not enough horizontal whitespace space between the contents of a matrix and the brackets surrounding it
12 open	`f(n) = \begin{cases} n/2, & \text{if }n\text{ is even} \\ 3n+1, & \text{if }n\text{ is odd} \end{cases}`	$f(n)={\begin{cases}n/2,&{\text{if }}n{\text{ is even}}\\3n+1,&{\text{if }}n{\text{ is odd}}\end{cases}}$	$f (n) = {\begin{matrix} n / 2, & if n is even \\ 3 n + 1, & if n is odd \end{matrix}$	$f (n) = {\begin{matrix} n / 2, & if n is even \\ 3 n + 1, & if n is odd \end{matrix}$	There's not enough horizontal whitespace after the brace in the 'cases' environment
13 open	`\begin{align} f(x) & = (a+b)^2 \\ & = a^2+2ab+b^2 \end{align}`	${\begin{aligned}f(x)&=(a+b)^{2}\\&=a^{2}+2ab+b^{2}\end{aligned}}$	$\begin{matrix} f (x) & = (a + b)^{2} \\ = a^{2} + 2 a b + b^{2} \end{matrix}$	$\begin{matrix} f (x) & = (a + b)^{2} \\ = a^{2} + 2 a b + b^{2} \end{matrix}$	The `\align` environment has moderately broken whitespace,
13 open	`\begin{align} a &= 1, & b &= 2, \\ c &= 3, & d &= 4, \end{align}`	${\begin{aligned}a&=1,&b&=2,\\c&=3,&d&=4,\end{aligned}}$	$\begin{matrix} a & = 1, & b & = 2, \\ c & = 3, & d & = 4, \end{matrix}$	$\begin{matrix} a & = 1, & b & = 2, \\ c & = 3, & d & = 4, \end{matrix}$	Another example, which perhaps more clearly demonstrates the problems: there is not enough space between separate equations on the same line as well as too much space before the equals signs.
14 open	`\begin{alignat}{2} f(x) & = (a-b)^2 \\ & = a^2-2ab+b^2 \end{alignat}`	${\begin{alignedat}{2}f(x)&=(a-b)^{2}\\&=a^{2}-2ab+b^{2}\end{alignedat}}$	$\begin{matrix} f (x) & = (a - b)^{2} \\ = a^{2} - 2 a b + b^{2} \end{matrix}$	$\begin{matrix} f (x) & = (a - b)^{2} \\ = a^{2} - 2 a b + b^{2} \end{matrix}$	and "alignat" is completely broken.
14 open T434424	`\begin{alignat}{3} f(a,b) & = (a+b)^2 && = (a+b)(a+b) \\ & = a^2+ab+ba+b^2 && = a^2+2ab+b^2 \end{alignat}`	${\begin{alignedat}{3}f(a,b)&=(a+b)^{2}&&=(a+b)(a+b)\\&=a^{2}+ab+ba+b^{2}&&=a^{2}+2ab+b^{2}\end{alignedat}}$	$\begin{matrix} f (a, b) & = (a + b)^{2} & = (a + b) (a + b) \\ = a^{2} + a b + b a + b^{2} & = a^{2} + 2 a b + b^{2} \end{matrix}$	$\begin{matrix} f (a, b) & = (a + b)^{2} & = (a + b) (a + b) \\ = a^{2} + a b + b a + b^{2} & = a^{2} + 2 a b + b^{2} \end{matrix}$	Too much space in alignat in MathMl and Client SVG
14 open T434424	`\begin{alignat}{4} r_1 &= l_1 + 0 &&= l_1,\ & r_2 + 0\cdot 0 &> l_2 \\ R_1 &= L_1 &&= L_1,\ & R_2 &< L_2 \\ \text{(right)} & \text{(left)} && \text{(left)} & \text{(right)} & \text{(left)} \end{alignat}`	${\begin{alignedat}{4}r_{1}&=l_{1}+0&&=l_{1},\ &r_{2}+0\cdot 0&>l_{2}\\R_{1}&=L_{1}&&=L_{1},\ &R_{2}&<L_{2}\\{\text{(right)}}&{\text{(left)}}&&{\text{(left)}}&{\text{(right)}}&{\text{(left)}}\end{alignedat}}$	$\begin{matrix} r_{1} & = l_{1} + 0 & = l_{1}, & r_{2} + 0 \cdot 0 & > l_{2} \\ R_{1} & = L_{1} & = L_{1}, & R_{2} & < L_{2} \\ (right) & (left) & (left) & (right) & (left) \end{matrix}$	$\begin{matrix} r_{1} & = l_{1} + 0 & = l_{1}, & r_{2} + 0 \cdot 0 & > l_{2} \\ R_{1} & = L_{1} & = L_{1}, & R_{2} & < L_{2} \\ (right) & (left) & (left) & (right) & (left) \end{matrix}$	A perhaps clearer example demonstrating the problem from the previous 2 rows
	`\begin{align} x & = & 1100&.1\overline{01110}\ldots \\ x\times 2^6 & = & 1100101110&.\overline{01110}\ldots \\ x\times 2 & = & 11001&.\overline{01110}\ldots \\ x\times(2^6-2) & = & 1100010101 \\ x & = & 1100010101/111110 \\ x & = & (789/62)_{10} \end{align}`	${\begin{aligned}x&=&1100&.1{\overline {01110}}\ldots \\x\times 2^{6}&=&1100101110&.{\overline {01110}}\ldots \\x\times 2&=&11001&.{\overline {01110}}\ldots \\x\times (2^{6}-2)&=&1100010101\\x&=&1100010101/111110\\x&=&(789/62)_{10}\end{aligned}}$	$\begin{matrix} x & = & 1100 & .1 \overline{01110} \dots \\ x \times 2^{6} & = & 1100101110 & . \overline{01110} \dots \\ x \times 2 & = & 11001 & . \overline{01110} \dots \\ x \times (2^{6} - 2) & = & 1100010101 \\ x & = & 1100010101 / 111110 \\ x & = & (789 / 62)_{10} \end{matrix}$	$\begin{matrix} x & = & 1100 & .1 \overline{01110} \dots \\ x \times 2^{6} & = & 1100101110 & . \overline{01110} \dots \\ x \times 2 & = & 11001 & . \overline{01110} \dots \\ x \times (2^{6} - 2) & = & 1100010101 \\ x & = & 1100010101 / 111110 \\ x & = & (789 / 62)_{10} \end{matrix}$	Another example of bad whitespace in align, this tiem with four columns. There should be no space between the digits before and after the binary point.
	`\begin{align} f(x) &= 2(x + 2) \\[20mu] &= 2x + 4 \\[8pt] &= 2x + 2^2 \end{align}`	${\begin{aligned}f(x)&=2(x+2)\\[20mu]&=2x+4\\[8pt]&=2x+2^{2}\end{aligned}}$	$\begin{matrix} f (x) & = 2 (x + 2) \\ = 2 x + 4 \\ = 2 x + 2^{2} \end{matrix}$	$\begin{matrix} f (x) & = 2 (x + 2) \\ = 2 x + 4 \\ = 2 x + 2^{2} \end{matrix}$	In the `align` environment extra vertical spacing instructions at line breaks written in terms of 'mu' and 'pt' units do not properly change the spacing
	`\begin{align}x = b_0 + \dfrac{a_1}{b_1} {{}\atop+} \\[28mu]\ \end{align} \! \begin{align} \dfrac{a_2}{b_2} {{}\atop+} \\[2mu] \ \end{align} \! \begin{align}\dfrac{a_3}{b_3} {{}\atop+}\end{align} \! \begin{align}\\[2mu] \dfrac{a_4}{b_4} +\, \cdots. \end{align}`	${\begin{aligned}x=b_{0}+{\dfrac {a_{1}}{b_{1}}}{{} \atop +}\\[28mu]\ \end{aligned}}\!{\begin{aligned}{\dfrac {a_{2}}{b_{2}}}{{} \atop +}\\[2mu]\ \end{aligned}}\!{\begin{aligned}{\dfrac {a_{3}}{b_{3}}}{{} \atop +}\end{aligned}}\!{\begin{aligned}\\[2mu]{\dfrac {a_{4}}{b_{4}}}+\,\cdots .\end{aligned}}$	$\begin{matrix} x = b_{0} + \frac{a_{1}}{b_{1}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{2}}{b_{2}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{3}}{b_{3}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{4}}{b_{4}} + \dots . \end{matrix}$	$\begin{matrix} x = b_{0} + \frac{a_{1}}{b_{1}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{2}}{b_{2}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{3}}{b_{3}} \binom{}{+} \end{matrix} \begin{matrix} \frac{a_{4}}{b_{4}} + \dots . \end{matrix}$	Workaround used to render Leibniz's continued fraction notation is broken. (Such workarounds are necessary because Mediawiki's LaTeX implementation doesn't support the usual LaTeX commands for positioning elements.)
	`\cfrac{a_1}{1+a_2-\cfrac{a_2a_3} {1+a_3+a_4-\cfrac{a_4a_5} {1+a_5+a_6- \ddots } } }`	${\cfrac {a_{1}}{1+a_{2}-{\cfrac {a_{2}a_{3}}{1+a_{3}+a_{4}-{\cfrac {a_{4}a_{5}}{1+a_{5}+a_{6}-\ddots }}}}}}$	$\frac{a_{1}}{1 + a_{2} - \frac{a_{2} a_{3}}{1 + a_{3} + a_{4} - \frac{a_{4} a_{5}}{1 + a_{5} + a_{6} - ⋱}}}$	$\frac{a_{1}}{1 + a_{2} - \frac{a_{2} a_{3}}{1 + a_{3} + a_{4} - \frac{a_{4} a_{5}}{1 + a_{5} + a_{6} - ⋱}}}$	Incorrect vertical spacing in cfrac
	`\bigl\{ {\textstyle \sum_{i=1}^n \alpha_i\beta_i} \mathrel{\big\|} n \in \N,\, a_i \in \mathfrak{a},\, b_i \in \mathfrak{b} \bigr\}`	${\bigl \{}{\textstyle \sum _{i=1}^{n}\alpha _{i}\beta _{i}}\mathrel {\big \|} n\in \mathbb {N} ,\,a_{i}\in {\mathfrak {a}},\,b_{i}\in {\mathfrak {b}}{\bigr \}}$	${\sum_{i = 1}^{n} α_{i} β_{i} \| n \in ℕ, a_{i} \in 𝔞, b_{i} \in 𝔟}$	${\sum_{i = 1}^{n} α_{i} β_{i} \| n \in ℕ, a_{i} \in 𝔞, b_{i} \in 𝔟}$	Vertical line explicitly set to use relation spacing (`\mathrel{\big\|}`) for use in set-builder notation has wrong spacing on the left side
	A block-level math element: <math display=block> y = f(x) </math>	A block-level math element: $y=f(x)$	A block-level math element: $y = f (x)$	A block-level math element: $y = f (x)$	Math with "block" display is centered rather than indented, and seems to have too much vertical whitespace above when used as part of a paragraph.

Sandwich issue

Listed on Phabricator T438945

In Vector2022 + latex-to-mathml-to-client-mathjax-svg, wide displayed math formulas that overlap a floating image are partially hidden by the image with no scrollbar to make the hidden part visible. When the formula overlaps with the caption of the image, both pieces of text are overlaid. Example from square pyramid (a div puts the following in a box to simulate a narrow window)

Client-side SVG mode:

A square pyramidal number is a natural number that counts the number of stacked spheres in a square pyramid. If the pyramid has $n$ layers, then it has $P_{n} = 1^{2} + 2^{2} + \dots + n^{2} = \sum_{x = 1}^{n} x^{2} = \frac{n (n + 1) (2 n + 1)}{6}$ spheres.

Server-side SVG mode:

A square pyramidal number is a natural number that counts the number of stacked spheres in a square pyramid. If the pyramid has $n$ layers, then it has $P_{n}=1^{2}+2^{2}+\dots +n^{2}=\sum _{x=1}^{n}x^{2}={\frac {n(n+1)(2n+1)}{6}}$ spheres.

Native MathML mode:

A square pyramidal number is a natural number that counts the number of stacked spheres in a square pyramid. If the pyramid has $n$ layers, then it has $P_{n} = 1^{2} + 2^{2} + \dots + n^{2} = \sum_{x = 1}^{n} x^{2} = \frac{n (n + 1) (2 n + 1)}{6}$ spheres.

Blockquote issue

T382267 fixed and T420668 when using the parsoid parser open

See

/BlockquoteLegacy Edited using the legacy parser
/BlockquoteParsoid Edited using the parsoid parser

The parser can be set via Special:Preferences#mw-prefsection-editing editing->Developer Tools->Use the new Parsoid wikitext parser set to "Always (Opt-In)" or "Never (Opt-Out)".

MathML only bugs

Math format inconsistencies primarily affecting MathML mode
Number	LaTeX markup	Server-side SVG	Client-side SVG	Client-side MathML	Notes
	`x : y : z`	$x:y:z$	$x : y : z$	$x : y : z$	Lack of space before colon
T410843	`p(a\|b)`	$p(a\|b)$	$p (a \| b)$	$p (a \| b)$	Pipe introduces spurious spacing in Firefox
	`\\|pq\\| = \\|p\\| \\|q\\|`	$\\|pq\\|=\\|p\\|\\|q\\|$	$‖ p q ‖ = ‖ p ‖ ‖ q ‖$	$‖ p q ‖ = ‖ p ‖ ‖ q ‖$	Norm introduces spurious spacing in Firefox
	`\begin{align} \sqrt5 \end{align}`	${\begin{aligned}{\sqrt {5}}\end{aligned}}$	$\begin{matrix} \sqrt{5} \end{matrix}$	$\begin{matrix} \sqrt{5} \end{matrix}$	`align` environment wreaks hilarious havoc with square roots in Safari
	`a \xrightarrow{\cong} b`	$a\xrightarrow {\cong } b$	$a \overset{≅}{\to} b$	$a \overset{≅}{\to} b$	The ≅ symbol above the arrow is not clipped (as in server-side SVG render, which took a workaround to avoid) but in MathML mode is positioned too far to the right.

Resolved issues

The following markup examples no longer appear to be problematic but are retained here as a convenient collection of test cases.

Issues which have been more or less resolved
Number	LaTeX markup	Server-side SVG	Client-side SVG	Client-side MathML	Notes
1a T434428 closed - resolved	`\Gamma \Delta \Theta \Xi \Omicron \Pi \Sigma \Upsilon \Phi \Chi \Psi \Omega`	$\Gamma \Delta \Theta \Xi \mathrm {O} \Pi \Sigma \Upsilon \Phi \mathrm {X} \Psi \Omega$	$Γ Δ Θ Ξ O Π Σ Υ Φ X Ψ Ω$	$Γ Δ Θ Ξ O Π Σ Υ Φ X Ψ Ω$	uses the wrong symbol – shouldn't be italicized.
T434456 closed - resolved	`\left(a\right)'`	$\left(a\right)'$	${(a)}^{'}$	${(a)}^{'}$	Missing prime symbol after lage right hand bracket. Main space example at Derivative#Rules for combined functions for quotient rule
T435705 resolved	`\overset{}\overrightarrow {AB}`	${\overset {}{\overrightarrow {AB}}}$	$\overset{}{\vec{A B}}$	$\overset{}{\vec{A B}}$	Empty overset renders yellow-red SVG error message "mover"
T434477 new task	`\textstyle \sum_{k=0}^{n-1} \frac{ \binom {n+1}k }{\binom n{k+1} }`	$\textstyle \sum _{k=0}^{n-1}{\frac {\binom {n+1}{k}}{\binom {n}{k+1}}}$	$\sum_{k = 0}^{n - 1} \frac{(\binom{n + 1}{k})}{(\binom{n}{k + 1})}$	$\sum_{k = 0}^{n - 1} \frac{(\binom{n + 1}{k})}{(\binom{n}{k + 1})}$	Binomial coefficients get hilariously wrongly sized when used from inside a text-style fraction.
T434504	`\bar x \bar m \bar{ABC}`	${\bar {x}}{\bar {m}}{\bar {ABC}}$	$\bar{x} \bar{m} \bar{A B C}$	$\bar{x} \bar{m} \bar{A B C}$	`\bar` does not behave as expected. Should be a consistent glyph not an overline of any arbitrary content
T437131	`\left / \frac{a}{b} \right \backslash`	$\left/{\frac {a}{b}}\right\backslash$	$/ \frac{a}{b} \$	$/ \frac{a}{b} \$	Automatically sized (`\left` and `\right`) slashes are not correctly sized
(unclear if all possible appearances of similar bugs are solved)	`\frac{\sum_{k=1}^N k^2}{a}`	${\frac {\sum _{k=1}^{N}k^{2}}{a}}$	$\frac{\sum_{k = 1}^{N} k^{2}}{a}$	$\frac{\sum_{k = 1}^{N} k^{2}}{a}$	Sum in a fraction uses the wrong format (should be inline style)
	`\C \setminus \{0\},\, \C \smallsetminus \{0\}`	$\mathbb {C} \setminus \{0\},\,\mathbb {C} \smallsetminus \{0\}$	$ℂ ∖ {0}, ℂ ∖ {0}$	$ℂ ∖ {0}, ℂ ∖ {0}$	`\smallsetminus` uses the wrong symbol, should be more horizontal than vertical and should be noticeably different from `\setminus`.
	`\varnothing`	$\varnothing$	$\emptyset$	$\emptyset$	`\varnothing` uses the wrong symbol
	`\parallel,\, \nparallel,\quad \shortparallel,\, \nshortparallel`	$\parallel ,\,\nparallel ,\quad \shortparallel ,\,\nshortparallel$	$∥, ∦, ∥, ∦$	$∥, ∦, ∥, ∦$	`\shortparallel` and `\nshortparallel` use the wrong symbols
T439455	`\leqslant,\, \nleqslant,\quad \geqslant,\, \ngeqslant`	$\leqslant ,\,\nleqslant ,\quad \geqslant ,\,\ngeqslant$	$⩽, ⪇, ⩾, ⪈$	$⩽, ⪇, ⩾, ⪈$	`\nleqslant` and `\ngeqslant` use the wrong symbols
T438388	`S_0 \subset S_1\subset \dots\subset S_r`	$S_{0}\subset S_{1}\subset \dots \subset S_{r}$	$S_{0} \subset S_{1} \subset \dots \subset S_{r}$	$S_{0} \subset S_{1} \subset \dots \subset S_{r}$	Ellipses made with `\dots` aren't vertically centered in contexts where they should be
16 new task open T435274	\begin{array}{\|c\|c\|c\|} a & b & S \\ \hline 0 & 0 & 1 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 1 & 1 & 0 \end{array}	${\begin{array}{\|c\|c\|c\|}a&b&S\\\hline 0&0&1\\0&1&1\\1&0&1\\1&1&0\end{array}}$	$\begin{matrix} a & b & S \\ 0 & 0 & 1 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 1 & 1 & 0 \end{matrix}$	$\begin{matrix} a & b & S \\ 0 & 0 & 1 \\ 0 & 1 & 1 \\ 1 & 0 & 1 \\ 1 & 1 & 0 \end{matrix}$	Lines between cells in the 'array' environment are not rendered at all. T377167 now reopened.
	{{box\|<math>\begin{align} x &= 1, \\ y &= 2.\end{align}</math>}} {{box\|<math>\begin{align} x &= 1, \\ y &= 2. \\ \end{align}</math>}}	${\begin{aligned}x&=1,\\y&=2.\end{aligned}}$ ${\begin{aligned}x&=1,\\y&=2.\\\end{aligned}}$	$\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$ $\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$	$\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$ $\begin{matrix} x & = 1, \\ y & = 2. \end{matrix}$	Adding `\\` at the end of the `align` environment causes pointless extra space at the bottom. Output should be identical with or without the trailing `\\`.
T437142	`\sideset{_a^b}{_c^d }\sum f(t)`	$\sideset {_{a}^{b}}{_{c}^{d}}\sum f(t)$	${}_{a}^{b}\sum_{c}^{d} f (t)$	${}_{a}^{b}\sum_{c}^{d} f (t)$	`\sideset` is pretty much completely broken even with the originally expected operators like `\sum`
T437142	`\textstyle \sideset{_a^b}{_c^d }\sum f(t)`	$\textstyle \sideset {_{a}^{b}}{_{c}^{d}}\sum f(t)$	${}_{a}^{b}\sum_{c}^{d} f (t)$	${}_{a}^{b}\sum_{c}^{d} f (t)$	It is broken in inline style as well
T437142	`\sideset{_a^b}{_c^d }\sum_{i=1}^{N} f(t)`	$\sideset {_{a}^{b}}{_{c}^{d}}\sum _{i=1}^{N}f(t)$	${}_{a}^{b}\sum_{c}^{d}_{i = 1}^{N} f (t)$	${}_{a}^{b}\sum_{c}^{d}_{i = 1}^{N} f (t)$	Surprisingly, it's more or less correct if the sum also has limits above/below (though the sideset symbols are a bit too close to the summation sign)
T437140	`\sideset{_a^b}{_c^d}D f(t)`	$\sideset {_{a}^{b}}{_{c}^{d}}Df(t)$	${}_{a}^{b}D_{c}^{d} f (t)$	${}_{a}^{b}D_{c}^{d} f (t)$	`\sideset` renders a blob of red text on yellow; this bug breaks Fractional calculus and probably other articles as well.
T437140	`\sideset{_a^b}{_c^d}{\mathop{D} } f(t)`	$\sideset {_{a}^{b}}{_{c}^{d}}{\mathop {D} }f(t)$	${}_{a}^{b}D_{c}^{d} f (t)$	${}_{a}^{b}D_{c}^{d} f (t)$	The above row is actually invalid LaTeX; the third argument is supposed to be a math operator. But a corrected version still breaks the MathML and client-side SVG renderers.
	`\mathop{X}_a^x`	$\mathop {X} _{a}^{x}$	$X_{a}^{x}$	$X_{a}^{x}$	`\mathop` does not work: should turn the content into an operator in the style of `\sum` Aside: as a feature request, it would be nice if all of the Wikipedia LaTeX renderers supported some command(s) along the lines of those provided by the scalerel package. There are several relatively common notations which are currently impossible to show correctly in Wikipedia because of the inability to resize symbols.
T435703 new task	`\underset{f'}\rightarrow`	${\underset {f'}{\rightarrow }}$	$\underset{f^{'}}{\to}$	$\underset{f^{'}}{\to}$	`\underset` is broken
	`\begin{align} \frac{\pi}{4} &= \sum_{n=0}^{\infty} \left(\frac{1}{4n+1}-\frac{1}{4n+3}\right) \\[6px] &= \sum_{n=0}^{\infty} \frac{2}{(4n+1)(4n+3)} \end{align}`	${\begin{aligned}{\frac {\pi }{4}}&=\sum _{n=0}^{\infty }\left({\frac {1}{4n+1}}-{\frac {1}{4n+3}}\right)\\[6px]&=\sum _{n=0}^{\infty }{\frac {2}{(4n+1)(4n+3)}}\end{aligned}}$	$\begin{matrix} \frac{π}{4} & = \sum_{n = 0}^{\infty} (\frac{1}{4 n + 1} - \frac{1}{4 n + 3}) \\ = \sum_{n = 0}^{\infty} \frac{2}{(4 n + 1) (4 n + 3)} \end{matrix}$	$\begin{matrix} \frac{π}{4} & = \sum_{n = 0}^{\infty} (\frac{1}{4 n + 1} - \frac{1}{4 n + 3}) \\ = \sum_{n = 0}^{\infty} \frac{2}{(4 n + 1) (4 n + 3)} \end{matrix}$	In `align` extra vertical spacing instructions at line breaks written in terms of 'px' units are visibly rendered instead of changing the spacing
T380654 reopened	`c(x) = \begin{cases} \dfrac{1+\sqrt{1-4x} }{2x} \\[4px] \dfrac{1-\sqrt{1-4x} }{2x} \end{cases}\,.`	$c(x)={\begin{cases}{\dfrac {1+{\sqrt {1-4x}}}{2x}}\\[4px]{\dfrac {1-{\sqrt {1-4x}}}{2x}}\end{cases}}\,.$	$c (x) = {\begin{matrix} \frac{1 + \sqrt{1 - 4 x}}{2 x} \\ \frac{1 - \sqrt{1 - 4 x}}{2 x} \end{matrix} .$	$c (x) = {\begin{matrix} \frac{1 + \sqrt{1 - 4 x}}{2 x} \\ \frac{1 - \sqrt{1 - 4 x}}{2 x} \end{matrix} .$	The above issue also affects the `cases` environment. This example is drawn from the article Catalan numbers.
	`\operatorname{gd} ({\pm \pi i} + \bar z) = \begin{cases} \pi - \overline{\operatorname{gd} z} \quad &\mbox{if }\ \ \operatorname{Re} z \geq 0, \\[5mu] -\pi - \overline{\operatorname{gd} z} \quad &\mbox{if }\ \ \operatorname{Re} z < 0, \end{cases}`	$\operatorname {gd} ({\pm \pi i}+{\bar {z}})={\begin{cases}\pi -{\overline {\operatorname {gd} z}}\quad &{\mbox{if }}\ \ \operatorname {Re} z\geq 0,\\[5mu]-\pi -{\overline {\operatorname {gd} z}}\quad &{\mbox{if }}\ \ \operatorname {Re} z<0,\end{cases}}$	$gd (\pm π i + \bar{z}) = {\begin{matrix} π - \overline{gd z} & if Re z \geq 0, \\ - π - \overline{gd z} & if Re z < 0, \end{matrix}$	$gd (\pm π i + \bar{z}) = {\begin{matrix} π - \overline{gd z} & if Re z \geq 0, \\ - π - \overline{gd z} & if Re z < 0, \end{matrix}$	Inconsistent overline thickness

Formatting notes

To add and example, use a line like

|-
|| {{phab|T1234}} status || {{/RowFormat| 1= \tbinom{n}{k} }} || Description

In one of the tables. This will automatically add four columns with the latex code,

There are some restrictions on the characters that you can use in parameters to the {{/RowFormat}} template. The character | is treated as a separator between template characters so can't be use directly, instead use the {{!}} special template that is converted to a pipe character in the template transclusion process. Double curly bracket either {{ or }} signify the start or end of a template to transclude. Here simply add a space between then, latex ignore the extra space.

example with pipe characters.
Number	LaTeX markup	Server-side SVG	Client-side SVG	Client-side MathML	Notes
1	`\left\| \frac 1 2 \right\|`	$\left\|{\frac {1}{2}}\right\|$	$\| \frac{1}{2} \|$	$\| \frac{1}{2} \|$	Produced with: {{/RowFormat\| 1= \left{{!}} \frac 1 2 \right{{!}} }}
2	`\overline{\frac{top}{bottom} }`	${\overline {\frac {top}{bottom}}}$	$\overline{\frac{t o p}{b o t t o m}}$	$\overline{\frac{t o p}{b o t t o m}}$	Produced with: {{/RowFormat\| 1= \overline{\frac{top}{bottom} } }} rather than {{/RowFormat\| 1= \overline{\frac{top}{bottom}} }} which causes errors.
3	<math>\left\|\overline{\frac{a}{b}}\right\|</math>	$\left\|{\overline {\frac {a}{b}}}\right\|$	$\| \overline{\frac{a}{b}} \|$	$\| \overline{\frac{a}{b}} \|$	Manual entry without using the RowFormat template. See souce code for format.

Adding Phabricator tasks

Task can be added to the Wikimedia Phabricator bug reporting system that the developers use. See mw:How to report a bug for the actual steps, how to log in and guidance on what makes a good bug report.

A few pointers for adding maths bugs

Go to https://phabricator.wikimedia.org/maniphest/task/edit/form/43/
Give a short description of the issue in the title say "\Omega rendered in italic rather than roman in Clientside SVG and MathML modes"
Under **Steps to replicate the issue** (include links if applicable):
- Add details of your preference setting: MathML only/MathML with SVG image (client side MathJax rendering)/MathML with SVG image (server side MathJax rendering)
- Add the math expression used say <math>\Omega</math>.
- Try to find the simplest example that creates the issue.
Under **What happens?**:
- Add a screenshot of the rendered equation, you can use examples from this page, its good if you can show the column headings.
- Add text describing why this is wrong
Under **What should have happened instead?**:
- Add a screenshot of the correctly rendered equation
- Add text describing why this is correct
Under **Other information** (browser name/version, screenshots, etc.):
- Say which browser you are using chrome/Firefox/safari is probably enough.
- Link to the Wikipedia article where the bug was first seen. Copy and paste the URL.
Add Math to the Projects section.

After creating the task you can then add parent tasks, typically

T375238 Client-side MathJax rendering problems
T375318 "MathML only" mode formatting bugs (mathmode=native)

You can do this using the "Edit related task -> Edit parent tasks" side bar option.