WebExtensions Experiements have many similarities to traditional add-ons, therefore a lot of general documentation is already available on developer.mozilla.org. The following questions and answers are specific to WebExtensions experiments and should help you with common issues.

Can I include a chrome.manifest in an experiment?

The experiments do not support the ‘chrome.manifest’, and it will be ignored if included in the experiments add-on source directory. If you need an URI which points to assets packaged within the experiment (e.g. an image, an additional .jsm file, a frame script, etc.), you can register a path with the resource: protocol handler.

Why is my experiment undefined on Beta and Release?

On Nightly, Dev Edition or unbranded builds, you can install unsigned experiments if you flip two preferences: xpinstall.signatures.required and extensions.legacy.enabled. However unsigned experiments cannot be installed on Beta or Release regardless of any preference settings.

If you have any more questions you can’t find an answer to please get in touch.