Tab-size initial value to 4?

This would be a suggestion for the CSS WG but I’m not on that mailing list and before I bother registering and submitting there — tried in the past, failed, I guess must be doing this thing very wrong —, I thought I’d ask for feedback here.

CSS Text Module specifies tab-size with an initial value of 8 (eight). Indeed most if not all browsers seem to render tabulation characters with the width of 8 space characters.

Today, this doesn’t make much sense. The web author reaction to tab-is-eight-spaces is generally WHOA THAT’S WAY TO BIG WHAT HAPPENED?!?

I propose changing the specified initial value to 4.

Why 4?

That seems to be the contemporary de facto standard, the value that most people expect.

A tab-size:4 initial value would be closer to the expectations of both authors and users (wild guess, I know). That would map more closely to the default values used in most code editors, including browser devtools;

  • Chrome devtools: tab-size:4 in “Edit as HTML” (and more).
  • Firefox devtools: -moz-tab-size:4 in “Edit as HTML” (and more).

2 is also a common value, but is more like a personal preference that some people use in their code editor of choice.


  • Web authors would display code and other types of tab-indented text in <pre> elements without having to convert tab characters to either 2 or 4 spaces because WHOA THAT’S WAY TO BIG WHAT HAPPENED? That would make use of author-specified tab-size optional, rather than mandatory.
  • View-source views in browsers would be more reasonably indented.


  • Breaking some ASCII art that uses tab characters and relies on tab-is-8-spaces.

[Send an email to with “subscribe” in the subject first. Or click on the “subscribe” link here.]

It’s precisely that breakage that’ll probably make this impossible. People unfortunately mix tabs and spaces together in practice, and expect them to stay aligned.

It’s not difficult to add a * { tab-size: 4; } at the top of your stylesheet. If you use a reset or normalize stylesheet, just throw it in there.

Feel free to file a bug on browsers to use a more reasonable tab-size value for their view-source pages; that doesn’t require any spec changes to fix.

Re. browser tools: looks like Firefox’s updated view-source (in Aurora) now uses tab-size:4. I opened a bug for Chromium.

I still believe web authors would benefit from a tab-size:4 initial value. I’ve witnessed many beginner authors trying to show code online and having to convert tabs to spaces (which they’re often not yet comfortable doing using a code editor) because the default tab-size made their code too wide to show comfortably. Of course now they could use tab-size:4 themselves, but they would have to know about it and know about current browser support etc., which is unlikely for beginners.

Not a very big use case in the grand scheme of things, but still.

I’ve browsed a few ASCII art galeries with tab-size:40 on, and they seem devoid of tab characters, but of course it might not be representative of actual web content people rely on.

Update on reasonable tab-size in developer tools:

  • Firefox now uses tab-size:4 in view-source and tab-size:2 in “Edit as HTML” boxes (probably to avoid big indentation in the “Edit as HTML” boxes which are generally not very wide, especially if devtools are docked to the right).
  • Chrome uses tab-size:4 in their devtools but still the default 8 in view-source (so I opened a bug).
  • Edge uses 4-space tabs in their Debugger view (which is their new “View Source” view), and 8-space tabs in their “Edit as HTML” view (bug report on Twitter).

Can you please file a bug regarding this on Edge via rather than referencing a tweet. Thanks!!

Apparently a Edge bug was filled here: and closed because Edge does not support tab-size.