What is the status of is-attributes (custom element type extensions)?

[jarek...@gmail.com]

Is it safe to rely on is-attributes in production code? From my read of the public-webapps mailing list they are unlikely to be standardised. What are the chances that they will be deprecated and removed from Chrome like e.g. /deep/ selector?

[Dominic Cooney]

It's hard to predict whether "is" will make it into the standard.

Nobody is working on removing "is" right now.

If "is" isn't implemented by other browsers, here's typically what would happen:

1. We would add a use counter for the "is" attribute. (We don't have a use counter for it now, but you can see the use counter for document.registerElement as an example of what one looks like.)

2. When use drops below a certain level, usually around 0.03% of page views, we would discuss removing "is" on blink-dev and start to print a deprecation message on the devtools console when a page uses "is". There's absolutely no guarantee about this 0.03% level, by the way, it is just a guide. It may be much higher (if there are extenuating circumstances like the availability of a different, standards-based API for the same purpose) or lower (if we're working on other stuff that is higher priority.)

3. In the some subsequent version of Chrome (maybe the very next one) we would stop processing the "is" attribute.

You can read more about our deprecation process on the wiki.

Hopefully you can use this to inform your own decision about whether to use "is".

HTH,

Dominic