The short history of the “about:” URL (2013) (opens in new tab)

Note this was written by Lou Montulli who also wrote the amusing post about "The Origins of the <Blink> Tag" [1]

[1] http://www.montulli.org/theoriginofthe%3Cblink%3Etag

I didn't know about the about:about url, and have since found a number of amusing and useful links, for example:

Chrome:

chrome://site-engagement/

chrome://net-internals/#dns

chrome://net-export/

chrome://indexeddb-internals/#

Firefox:

about:mozilla

about:memory

about:robots

I'm Lou and I'm the author of that article.

If you have any questions I'm happy to answer them.

Firefox has a list of all "about:" pages at about:about

Not everything works in about:blank.

For example, if you go into devTools and try to build an SVG programmatically (or simply inject some innerHTML), the funcURLs won't pick up the ids in the <defs> section for things like gradients/patterns/etc.

I can't remember which part of which spec conflicts with the other on this. I just remember mentioning it on the SVG list and the Mozilla bug list. (It actually works in Chrome, which a Mozilla dev told me is a bug in Chrome. :)

slightly ot, but, if anyone else was distracted by the use of 3-4 spaces between each sentence, this JS snippet will fix it:

    document.querySelectorAll("td>div").forEach(x=>(x.innerHTML = x.innerHTML.replace(/ /g, " ")))

The complete list of to-date about:mozilla passages: https://www.mozilla.org/en-US/book/

I've always loved this easter egg.

about:legacy-compat made its way into HTML5 as the system identifier/URL of a (fictive) external SGML declaration set to contain declarations for the elements and attributes of HTML. It's required to make an HTML5 document a valid SGML application; if it weren't there, the declaration set would be treated as containing no declarations at all, which doesn't work for eg. empty (HTML "void") elements such as img and br, and also for writing enumerated attributes in their short forms such as in <option selected> etc.