Getting started with firefox-addon – Installing a Temporary Add-on

To test an add-on you are developing, you will likely desire to install it in Firefox temporarily. You can do so by loading it as a Temporary Add-on. To do so:

  1. Go to about:debugging
  2. Click on "Load Temporary Add-on"
  3. In the file picker, navigate to the directory containing the add-on files
  4. Select any file in the folder
  5. Click "Open"

The following animation shows loading an add-on named "aaaaaaaaaaaaaaaaaa – demo add-on" from about:debugging and that the add-on then shows up in about:addons:

loading a temporary add-on

As a Temporary Add-on, you can load either an unpacked add-on (a directory which contains all files for the add-on which you would pack into an .xpi file), or an add-on which is packed into an .xpi archive. Temporary Add-ons do not need to be signed. Temporary Add-on remain installed until manually uninstalled, or Firefox restarts.

Mozilla documentation: Temporary Installation in Firefox

WebExtensions

WebExtensions can be loaded as Temporary Add-ons. This can be done with the add-on files either unpacked, or packaged in an .xpi file.

Firefox Add-on SDK

You can not load a Firefox Add-on SDK extension as a temporary add-on without first packaging it into an .xpi file with jpm xpi. In general, you will use jpm run to test your Firefox Add-on SDK extension.

The files which are typically edited for an Add-on SDK extension do not make a complete extension without some additional wrapping functions and the package.json file being translated into an install.rdf file and, possibly, a chrome.manifest file. This process wraps the Add-on SDK extension into a Bootstrap/Restartless add-on, which is understood by Firefox. Without this process, Firefox will not be able to load the add-on. This process is performed by jpm xpi resulting in a packed .xpi file. Executing jpm run also performs this process, but stores the resulting files in a temporary location and invokes Firefox with the add-on installed.

Bootstrap/Restartless

Bootstrap/Restartless add-ons can be loaded as Temporary add-ons. This can be done with the add-on files either unpacked, or packaged in an .xpi file.

Legacy/Overlay/XUL

Legacy/Overlay/XUL add-ons can not be loaded as temporary add-ons.

if you want to reproduce, please indicate the source:
Getting started with firefox-addon – Installing a Temporary Add-on - CodeDay