Product analytics for browser extensions

Do you have a Firefox or Chrome browser plugin with a user interface and want to understand how it's being used? PostHog is the perfect way to do just that.

Setup for Firefox & Chrome plugins

Installing PostHog inside your plugin

Open the HTML file used in your default_popup and add the PostHog array.js script. To do this you'll need to either:

1. Copy the latest version of array.js from: https://app.posthog.com/static/array.js and import it locally using <script src="array.js" /> before the </head> tag
2. If you're packaging your plugin automatically use the npm module for posthog.js

All you need to do now is initialize PostHog, add the following code to a new js file and import it into your default_popup html file to initiate PostHog.

posthog.init('your_project_token',{api_host:'https://app.posthog.com',persistence:'localStorage'})

• your_project_token - This is the Project API key which can be found on PostHog under Project Settings
• api_host - This is the URL to your PostHog instance (if you're not using PostHog Cloud)
• persistence - This indicates we should store user data in localStorage rather than cookies - there are issues with cookie persistence on Firefox plugins

Tracking events

One of the best things about using PostHog is, all the interactions like clicks will automatically generate events in PostHog, so you don't need to do anything else to start analyzing.

If you'd like to instrument your own custom events, all you need to do is:

posthog.capture('custom_event_name', {})

See our browser JS library guide for more details

Session replay

Due to the new content security policies in Manifest v3 about unsafe-eval and remote code execution, importing only array.js isn't enough since the array.js code will try to load the the recorder from the PostHog CDN. This will be blocked by the browser.

To fix this instead of importing the array.js, you can import the array.full.js, follow the install step 1. but instead of using the former use the latter from https://app.posthog.com/static/array.full.js, also remember to change the script src to array.full.js or follow the install step 2. and install the npm module for posthog.js.

Import the recorder to avoid the remote code execution if using the script from the step 1.

import "posthog-js/dist/recorder.js"

Import the recorder to avoid the remote code execution if using the npm module from step 2.

import rrwebRecord from "posthog-js/dist/recorder"