# AMO API inconsistent with Firefox behavior

**URL:** <https://discourse.mozilla.org/t/amo-api-inconsistent-with-firefox-behavior/11262>\
**Category:** addons.mozilla.org\
**Created:** [October 3, 2016, 5:41pm UTC](https://discourse.mozilla.org/t/amo-api-inconsistent-with-firefox-behavior/11262 "2016-10-03T17:41:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![XZS](https://avatars.discourse-cdn.com/v4/letter/x/da6949/32.png) [@XZS](https://discourse.mozilla.org/u/XZS)\
**Post date:** [October 3, 2016, 5:41pm UTC](https://discourse.mozilla.org/t/amo-api-inconsistent-with-firefox-behavior/11262/1 "2016-10-03T17:41:16Z")

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While packaging the extension for Arch Linux, I found that [the GNOME Keyring integration extension](https://addons.mozilla.org/en-US/firefox/addon/mozilla-gnome-keyring/) installs just fine on my Firefox 49, despite [the API](https://services.addons.mozilla.org/de/firefox/api/1.5/addon/mozilla-gnome-keyring) reporting it only to be compatible up to version 45.\*. Add-On compatibility checking was not manually disabled.

I expected this API path to be exactly the place a Firefox installation queries to see whether a locally installed Add-On is compatible. Where can I find the compatibility information Firefox actually considers?

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**Author:** ![jorgev](https://avatars.discourse-cdn.com/v4/letter/j/71c47a/32.png) [@jorgev](https://discourse.mozilla.org/u/jorgev)\
**Post date:** [October 4, 2016, 8:04pm UTC](https://discourse.mozilla.org/t/amo-api-inconsistent-with-firefox-behavior/11262/2 "2016-10-04T20:04:26Z")

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Compatibility is a complicated thing. Firefox by default will ignore the `maxVersion` in an add-on and assume it’s compatible. Exceptions to this rule are:

- If the add-on includes the `strictCompatibility` flag in its manifest. In this case the `maxVersion` determines compatibility. It looks like the API doesn’t expose that flag, though.
- If a compatibility problem and a compatibility override is added by an admin. This could even override versions included between the max and min versions in the add-on manifest. Also not exposed in the API.