Best Practices for Implementors
From WHATWG Wiki
Adding new features
- Before adding a new feature, even one that's as simple as a new <meta> value, please ensure you have discussed it with other browser vendors. You can use the email@example.com mailing list for this purpose.
- If you're adding a feature that's not in a spec, make sure to first address any concerns that the relevant spec's editor may have. You might have missed some reason why it's not in the spec. If the spec's editor has given reasons why the feature is a bad idea, but you think you should implement it anyway, make sure to make this clear in public both to the editor in question and to other browser vendors.
- If there are multiple specs that could apply, e.g. because it cross multiple topics or because the spec in question is forked, make sure to raise it with all the relevant editors, not just one of them.