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Temporary Installation in Firefox

This article describes how an add-on developer can temporarily install an add-on in Firefox for testing and debugging. The add-on will stay installed until you restart Firefox. You can use this method with any kind of restartless add-on, including bootstrapped extensions and Add-on SDK add-ons. As of Firefox 55, the add-on developer temporarily install will remain after closing of Firefox.

Note that this is not how end users should install add-ons in Firefox. End users will install add-ons by downloading and opening packaged add-ons that have been signed by Mozilla. To learn how a WebExtension developer can get such a packaged, signed add-on, see Publishing your WebExtension.

To install an add-on temporarily:

  • open Firefox
  • enter "about:debugging" in the URL bar
  • click "Load Temporary Add-on"
  • open the add-on's directory and select any file inside the add-on.

The add-on will be installed, and will stay installed until you restart Firefox.

Reloading a temporary add-on

Starting in Firefox 48, there's a new button labeled "Reload" next to the add-on's entry in about:debugging:

This does what it says:

Note that in Firefox 48 only, "Reload" does not update the add-on's name and description that are displayed in about:debugging and about:addons. This is fixed in Firefox 49.

Using the command line

If you are already using the command line for development, check out the web-ext tool. It automates the temporary installation step and automatically reloads your extension when its source code changes.

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 Contributors to this page: hellosct1, wbamberg, kumar303
 Last updated by: hellosct1,