How to migrate legacy extension preferences

Eric Bixby eric.k.bixby at
Sat Sep 30 23:06:34 UTC 2017

This blog post might be more helpful:

The article has a link to some example code.  You basically want to create
an embedded web-extension (or hybrid).

On Sat, Sep 30, 2017 at 2:22 AM, Neil Bird <lists at> wrote:

>   OK, so I have to use the new storage API for prefs. going forward, but
> I have found the following page confusing:
>   I have no idea what this page is telling me to do in order to ensure
> my users' prefs are migrated.  I think it's telling my add-ons prefs in
> prefs.js will be deleted upon FF57, and I need to have read them and
> re-written them to the storage API before then, even if I shan't get a
> new version of the extension released by then.
>   But under what circumstances can I do that?  Can I get at the storage
> API from my existing “legacy” code & upload a new version to migrate it
> in the meantime, or what?
>   Will I still be allowed to upload “legacy” format extensions in the
> short term (to allow this preparation)?  I had thought I read they were
> going to be rejected (although, of course, they'll still work with ESRs
> for a while).
>   If that's the case, I shall need to put my efforts now not into
> migrating the extension, but putting out an interim version that
> migrates the pref's. data.
> --
> [phoenix at fnx ~]# rm -f .signature
> [phoenix at fnx ~]# ls -l .signature
> ls: .signature: No such file or directory
> [phoenix at fnx ~]# exit
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