Difference of the "Browser." and "Messenger." when using a webextension/javascript API

Question

Good day, I am new to using webextension and javascript apis. Just wondering what is the difference of using messsenger.(API) and Browser.(API)

Answer 1

I'm not 100% sure, but my understanding is that the following: Both browser and messenger are namespaces that can be used to call WebExtension API in Thunderbird. I suppose that browser exists because it was inherited from Firefox, from which Thunderbird gets some of the code for WebExtensions (they have many APIs in common). But Thunderbird is not meant to be a browser, above all it's an email client. So I suppose the messenger namespace was added to reflect that.

This seems to be corroborated by the documentation for the MailExtensions API

In Thunderbird, all WebExtension API can be accessed through the browser.* namespace, as with Firefox, but also through the messenger.* namespace, which is a better fit for Thunderbird.

I would see it pretty much as the same thing as WebExtensions being called indifferently WebExtensions or MailExtensions for Thunderbird.

Assuming my hypothesis is correct, there should be no practical difference in using one over the other.