> For the complete documentation index, see [llms.txt](https://developer.thunderbird.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.thunderbird.net/add-ons/updating/tb78.md).

# Update for Thunderbird 78

{% hint style="info" %}
Support for legacy WebExtensions was removed from Thunderbird Beta version 74, released in February 2020. Only modern WebExtensions are now compatible with Thunderbird 78.
{% endhint %}

## Required Changes

There are two types of changes which are required to make your legacy extensions compatible with Thunderbird 78:

* The legacy WebExtension must be converted to a modern WebExtension

{% content-ref url="/pages/DTjHmbwJ51QK1bJWb9zY" %}
[Convert legacy WebExtensions to modern WebExtensions](/add-ons/updating/historical-overview/legacy-to-modern.md)
{% endcontent-ref %}

* All extensions need to be updated to reflect changes in Thunderbird core, like renamed/replaced API calls, removed support for some XUL elements and much more.

{% content-ref url="/pages/-LmPscFTyqiM9ltgchMv" %}
[Adapt to Changes in Thunderbird 69-78](/add-ons/updating/tb78/changes.md)
{% endcontent-ref %}

## Additional Tips

{% content-ref url="/pages/-LclSX0RLl8c4AuEWlWp" %}
[Tips and Tricks](/add-ons/resources/tips-and-tricks.md)
{% endcontent-ref %}