I wish to review my Firefox Extensions, specifically I want to know the date when I installed all my extensions. Is this possible?

I know about Review installed extensions | Firefox Help support article but it's not helpful. And I know about about:addons

2 Answers 2


I am assuming Windows here. Go to %APPDATA%\Mozilla\Firefox\Profiles\. Go into your profile and then find extensions.json.

Each extension should have an installDate attribute. It will be in Epoch time (e.g. 1553267439302) so you'll want to convert it to a human readable format. Also has a defaultLocale | Name attribute which has the extension name in it.

  • Thanks for giving me the idea of how to do it. It's not particularly user friendly. I viewed the extension.json in Firefox and it had a nifty expandable tree view but I couldn't work out some of the extensions. I found the id attribute but that was sometimes gobbledy gook. Dec 23, 2019 at 16:50
  • 1
    Yeah I have a few of those as well. I couldn't find any listings to reconcile those. There might be a workaround you can try though. Go into the extensions folder and find the .xpi files with those GUID names. Drag the files into Firefox as a new tab and it should try to install those extensions, you can always cancel it. For me, they were mostly just Themes.
    – MC10
    Dec 23, 2019 at 16:58
  • This is all so fiddly. I wish there was an extension or web app where we can drop the extensions.json file to find a sortable list or table with extension name and install date. Ideally this would be in the about:addons page. I am also asking on Addons.Mozilla.org forum and support.mozilla.org forum. Dec 23, 2019 at 17:29
  • Kind of like Session History Scrounger for Firefox (with lz4 support) — Fx File Utilities but for extensions.json Dec 23, 2019 at 17:37

Firefox Extension Tracker, a one page web app, was kindly created by Jefferson Scher in response to my questions via this Issues post on his Github repo for Session History Scrounger for Firefox (with lz4 support) — Fx File Utilities. FireFox Extension Tracker displays for Extensions: Name and Version; installation date and updated date; Status; and ID and source. It solved all my original question but didn't solve my later wishes for sortable list but that may be in a future version.

To use:

  1. Press ⊞ Win + R
  2. Type into the text box %APPDATA%\Mozilla\Firefox\Profiles\.
  3. Select your profile (usually folder with .default)
  4. Find extensions.json
  5. Goto https://www.jeffersonscher.com/ffu/extensionsjson.html
  6. Drag and drop the previous extensions.json file into the Drop File Here box.
  7. The information is now displayed

Firefox Extension Tracker

With thanks to MC10 for pointing out the keywords to search for and where to look to get more help.

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