# How to detect if WebExtension addon is installed?

**URL:** <https://discourse.mozilla.org/t/how-to-detect-if-webextension-addon-is-installed/9398>\
**Category:** Development\
**Created:** [June 23, 2016, 3:48pm UTC](https://discourse.mozilla.org/t/how-to-detect-if-webextension-addon-is-installed/9398 "2016-06-23T15:48:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ofer](https://sea1.discourse-cdn.com/flex001/user_avatar/discourse.mozilla.org/ofer/32/21819_2.png) [@ofer](https://discourse.mozilla.org/u/ofer)\
**Post date:** [June 23, 2016, 3:48pm UTC](https://discourse.mozilla.org/t/how-to-detect-if-webextension-addon-is-installed/9398/1 "2016-06-23T15:48:10Z")

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I’m developing a firefox add on, using the new web extension mechanism. Now I need to check in my web page if the extension is installed. I know that in chrome you have: chrome-extension://nnhadaeaehpngjcegobbnogakdapkiph/{your content} Is there something like that in firefox? Is there an alternative way?

Best,

Ofer

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**Author:** ![erosman](https://sea1.discourse-cdn.com/flex001/user_avatar/discourse.mozilla.org/erosman/32/15447_2.png) [@erosman](https://discourse.mozilla.org/u/erosman)\
**Post date:** [June 24, 2016, 4:43am UTC](https://discourse.mozilla.org/t/how-to-detect-if-webextension-addon-is-installed/9398/2 "2016-06-24T04:43:59Z")

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Developers often add a classname (or other identifier) to an element on the page (e.g. body) with the addon, that can be picked up by the site.

However … please note that, … Any tracking (e.g. affiliate/referral/install/uninstall/upgrade/disable/error etc) to outside sources requires clear disclosure in both the add-on description and the Privacy Policy.