For some reason, it appears that writing an answer can become really slow for me when I use Safari. This happens especially when the answer gets a bit long. Has anyone else encountered this?

  • $\begingroup$ Not all the time and different browsers do behave different for me here… but “yes”, when Q&As get longer, or when there are more than a handfull of answers (which increases pagelength accordingly) I tend to experience smaller hickups due to render-lagging while the browser tries to repaint its client area. I suspect MathJax causes this, due to being a bit too eager to re-render things during edits and scrolling. On my system it’s only a few millisecs per sec, but it made me fall back on Firefox for the time being (lags too, but handles this best when comparing the Safari/Chrome/Firefox trio). $\endgroup$
    – e-sushi
    Jan 10, 2016 at 7:28
  • $\begingroup$ Thanks; disabling the fast preview and assistive MML seems to have helped. $\endgroup$ Jan 10, 2016 at 15:36
  • $\begingroup$ @IlmariKaronen I'd suggest adding your comment as an answer. I had no idea you could right click on a MathJax formula and change how it is rendered, etc. $\endgroup$
    – mikeazo
    Jan 11, 2016 at 13:19
  • $\begingroup$ There's now a user script by Davide Cervone (one of the MathJax devs) that improves MathJax preview while editing considerably. While the improved preview code will likely be eventually merged into the Stack Exchange editor itself, in the mean time I very much recommend installing the script. $\endgroup$ May 16, 2016 at 14:27

1 Answer 1


MathJax is one likely cause of slow editing — parsing and rendering math formulas can be kind of slow, and the live preview in the editor triggers a reparse on every keypress.

Some things you can try include:

  1. Change the math renderer. You can do this by right-clicking any math formula and selecting Math SettingsMath Renderer from the context menu that pops up:


    The default renderer here on Crypto.SE seems to be the old "HTML-CSS" renderer, but the MathJax version we have also supports the newer "Common HTML" renderer, which may be somewhat faster and more responsive.

    You can also try the SVG or MathML renderers, or, for absolute maximum speed, the "PlainSource" renderer, which just shows the unprocessed LaTeX source.

  2. Disable fast preview and assistive MML. The same context menu also has two on/off options labeled "Fast Preview" and "Assistive MML". Unchecking both of them should speed up MathJax rendering a bit.

    Assistive MML is an accessibility feature for visually impaired users with screen readers, and should be 100% safe to uncheck unless you're using one. Fast Preview, on the other hand, is a feature to speed up initial math display, by first pre-rendering all the math on the page with a "quick and dirty" renderer (IIUC, same as "Fast HTML" in the menu) before actually rendering them properly with the chosen renderer. While it makes math appear to render faster, the extra rendering pass actually takes more time overall.

  3. Disable MathJax while editing. Robjohn from Math.SE has a couple of bookmarklets to temporarily disable MathJax rendering (and also to enable MathJax in chat, which some folks might find useful). Just follow the instructions on the linked page.

Update: Davide Cervone (one of the MathJax developers) has released a user script that makes MathJax render faster while editing, and also includes a handy "Disable MathJax" checkbox for those times when even the improved MathJax preview is still too slow (basically replacing the bookmarklets by Robjohn mentioned above). I very much recommend installing it.

  • $\begingroup$ That last update should probably deserve it's own topic as feature request. $\endgroup$
    – Maarten Bodewes Mod
    May 17, 2016 at 9:43
  • $\begingroup$ @MaartenBodewes: If you mean making Davide's improved MathJax editing code the default, that's apparently already planned. $\endgroup$ May 17, 2016 at 9:54

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