Deprecating features in Firefox

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When we plan to remove a feature in Firefox, release management suggests these guidelines for deprecation.

Because our user population on our development channels are very different from the release users, we can gather data to give a good indication of what is going to happen when a feature is removed from the release. This can also help us to make our users happier by giving them clear information about what to do if they are using a feature that's being phased out of the main product.

Preliminary steps

• Consider gathering telemetry or FHR information on the feature to assess user impact. We can potentially distinguish between a feature rarely used by a bunch of scattered people vs. a feature heavily used by a handful of people and not used at all by others.
• Email relevant lists such as firefox-dev, dev-platform, or dev-security with an intent to deprecate announcement. This may reveal related issues or interesting use cases for the feature.

Provide information for users

• Try to let the users of the feature know it will be going away (in the ui, in error or console warnings)
• Document how users of the feature can work around its deprecation (in a blog post, on MDN, in bugs, in a relnote)

Example

For something like a context menu item, when the item is clicked, we could show a notification to inform people that the feature will be removed in the next release. That notification could link to documentation that describes a workaround or suggests relevant addons.