Today we are entering the public beta phase of MathJax v2.6. This release focused on two main features:

Completing the CommonHTML output, a faster HTML output that can be generated on both client and server.

Accessibility improvements in the form of
 an extension to expose MathJax’s internal MathML to screenreaders
 making the MathJax Menu accessible.
The v2.6 release also includes over 30 bug fixes to increase the quality and stability of MathJax (see below for details).
The beta is available via our CDN at beta.mathjax.org/mathjax/latest/MathJax.js which you can load it in place of the version you are currently using. Alternatively, you can get a ZIP archive or access the branch on GitHub.
Please note the following.
Changes to the default MathJax “TeX” fonts
We have updated our default MathJax “TeX” fonts to improve the CommonHTML output and simplify its layout process. If you have previously installed a copy of the MathJax TeX fonts to your local system, please update that copy to ensure correct rendering in the CommonHTML output.
You can check this using the embedded page below (external link) which will detect whether you need to update installed MathJax “TeX” fonts installed.
See the Pen MathJax Font Check by MathJax (@mathjax) on CodePen.
Note: Other applications may have installed the MathJax “TeX” fonts for you.
Note: The changes to the MathJax “TeX” fonts are backward compatible to previous versions of MathJax so you can install them without worrying about sites using older MathJax versions. Of course you do not need to install the fonts as MathJax can automatically load webfonts instead.
Changes to the combined configuration files
If you are using a combined configuration, please note the following:

We have added several new combined configuration files. In particular, you can use the new CommonHTML output by chosing a combined configuration ending on
_CHTML
. 
The new
AssitiveMML.js
extension is included in these configurations. If you want to deactivate it, add, e.g., the following to your page beforeMathJax.js
is loaded.
Remember that this is still beta software, so if you are not an experienced user, you may want to wait for the official 2.6 release. We do not recommend that you use the 2.6beta version for production environments, but do encourage you to test your content with it.
If you are linking to http://cdn.mathjax.org/mathjax/latest/MathJax.js, note that at the point of the official release of v2.6, the address will begin to serve MathJax v2.6. You can also continue to use v2.5 by linking to http://cdn.mathjax.org/mathjax/2.5latest/MathJax.js instead — and you can change to that version at any point (it is available now). Once the official v2.6 release is made, the v2.6beta address will be removed from the CDN.
The official release of v2.6 should occur within the next three weeks, but we want you to be able to start to test out the v2.6 features now. Please report any bugs you find to the issue tracker at https://github.com/mathjax/MathJax/issues.
Thanks for your continuing interest in MathJax. We hope that this release makes your MathJax experience even better.
The MathJax Team.
New in MathJax v2.6
MathJax v2.6 includes a number of new features, as well a more than 30 important bug fixes. The following are some of the highlights.
Features
 Improved CommonHTML output. The CommonHTML output now provides the same layout quality and MathML support as the HTMLCSS and SVG output. It is on average 40% faster than the other outputs and the markup it produces are identical on all browsers and thus can also be pregenerated on the server via MathJaxnode. The fast preview mechanism introduced in v2.5 continues to develop as a separate output as PreviewHTML and the fastpreview extension.
 Accessibility improvements. We thank the AT community for their guidance, support, and feedback in our efforts towards making MathJax completely accessible to all users.
 Screenreader compatibility. The new
AssistiveMML
extension enables compatibility with most MathMLcapable screenreaders by inserting visuallyhidden MathML alongside MathJax’s visual output. See screenreader support for details on the expected behavior as well as background on the limitations due to lack of web standards and browser/OS technology.  Accesssible UI. We have improved the accessibility of the MathJax menu to enable assistive technology users to easily access its features, cf. MathJax UI.
 Screenreader compatibility. The new
 Semislim MathJax repository for bower. You can now use
bower install components/MathJax
for a fork of MathJax without PNG fonts. Many thanks to @minrk from the IPython/Jupyter team and to the team at components!  Deprecated: MMLorHTML extension. We have deprecated the
MMLorHTML
extension. For a detailed guide on configuring MathJax to choose different outputs on different browsers, please see Automatic Selection of the Output Processor for more information.
Numerous bugs and issues have also been resolved; for a detailed listing please check the release milestone.
Interface
 #938 Expose MathML for accessibility; cf. screenreader support.
 #939 Make MathJax contextual menu properly accessible.
 #1088 MathJax Menu: drop PNG images in menu.
 #1210 Update
MathZoom.js
: global borderbox support. Special thanks to @CalebKester
HTML/SVG/nativeMML display
 #1095 HTMLCSS output: prevent collapse of table borders.
 #596 SVG Output: Fix overlapping equation labels in SVG output
 #994 SVG Output: Change default
blacker
setting to 1.  #995 SVG output: fix baseline alignment issues.
 #995 SVG output: fix failure to scale all but the first glyph in a fraction when
useFontCache=false
.  #1233 SVG output: make maligngroup and malignmark produce no output.
 #1035 PreviewHTML output: fix fractions formatting in WebKit and IE.
TeX emulation
 #567 Add macro for
overparen
andunderparen
to provide stretchy arcs above/below  #956 Simplify the
mhchem
extension to use multiscripts, cf. #1072.  #1028 Fix spacing in
\alignedat
.  #1194 Fix problem where automatic numbering affects
\binom
and friends.  #1199 Fix problem with dot delimiter not being recognized as a delimiter.
 #1224 Handle braces properly in text mode when looking for matching math delimiters.
 #1225 Fix
\operatorname
not ignoring\limits
that follow immediately after.  #1229 Fix wrong spacing of trailing binary operators.
Asciimath
 asciimath/#31 Add support for
overparen
,underparen
to producemover
andmunder
constructs.
MathML
 #1072 Rightjustify prescripts in
mmultiscript
elements (after clarification in MathML 3 editors’ draft); cf. #956.  #1089 Fix
toMathML
from changing<maligngroup>
to<malign>
 #1188 Fix
mmultiscripts
with odd number of postscripts not rendering correctly.  #1231 Fix
<math>
element not being treated as an<mrow>
for embellished operator spacing.  #1233 Make
<maligngroup>
and<malignmark>
be selfclosing in MathML input.  #1238 Fix Content MathML extension not handling namespace prefixes.
 #1257 Improve
mml3.js
: better RTL support in HTMLCSS; improved IE/Edge compatibility.
Fonts
 #928 Add data for stretchy
U+2322 (FROWN)
,U+2323 (SMILE)
, and alsoU+2312 (ARC)
to be aliases for the top and bottom parentheses. This enables stretchy constructions; cf. also #567.  #1211 Fix web font detection for GyrePagella etc. in IE10+.
 #1251 Fix primes in STIXweb font being too small in SVG output.
Localization
 #1248 Updated locales thanks to the contributors at Translatewiki.net; activate locales for Bulgarian, Sicilian, and Lithuanian.
APIs
 #1216 Add debugging tips to console output.
Misc.
 #1074 Fix regression in v2.5 regarding MathPlayer on IE9.
 #1036 Improve CDN rollover behavior.
 #1085 Fix detection of Windows Phone mobile IE.
 #1155 Work around websites using user agent filtering
 #1173 Avoid warning message in debug mode.
 #1208 Fix CHTML preview from setting chunking parameters even when disabled.
 #1214 semislim official MathJax repository for bower; use
bower install components/MathJax
for a copy without PNG fonts. Special thanks to @minrk from the IPython/Jupyter team and to the team at components!  #1254 Improve examples in
/test
: add viewport meta tags, improve dynamic examples.