Required steps to update add-ons for Thunderbird Beta.
This section covers the required update steps for add-ons which are already compatible with Thunderbird 91 and need to be made compatible with Thunderbird Beta (91+).
Changes in WebExtension APIs
Our WebExtension APIs are meant to be stable, but we are adding new features and since this is a very young technology this might also require backward incompatible changes. All WebExtension API changes are listed in our API documentation: