Hakarasenai — Google Analytics Opt-out door omikuji

Google publishes an official Google Analytics opt-out add-on, and there is a Firefox build of it. The trouble is how it works: it injects a script element into the page, and Firefox applies the page's own Content Security Policy to content scripts. On any site with a strict CSP the injection is blocked and the opt-out quietly does nothing — and nothing tells you it failed.

Hakarasenai uses the same official opt-out hook, but puts it where no CSP can reach it, and adds network blocking behind it as a second layer.

What it does

1. Tells the Google Analytics code on the page that you have opted out. The flag is the one Google Analytics reads itself (window._gaUserPrefs.ioo), set from a content script running in the page's own world at document start, so there is nothing in the DOM for a CSP to block.
2. Blocks the measurement hits. Five static declarativeNetRequest rules cover the /collect and /batch endpoints on google-analytics.com and analytics.google.com, including the regional hosts, plus stats.g.doubleclick.net.
3. Lets you exclude one site at a time from the toolbar button, if you actually want to be measured — verifying Analytics on your own site, for instance. Exclusions cover subdomains and turn off both layers.

What it does not block

The Tag Manager loader (gtag.js, gtm.js) and the scripts served by google-analytics.com are left alone. Opting out means letting the code load and not letting it report; taking out the loader would break whatever else a site drives through Tag Manager. No page resource is blocked, so this practically never breaks a site.

What it cannot do

Server-side tagging that collects on a site's own domain cannot be told apart from ordinary traffic to that site, so the blocking layer cannot catch it — the opt-out flag still applies there. Analytics products other than Google Analytics are out of scope.

Privacy

It collects nothing, sends nothing anywhere, and makes no network requests of its own. The only stored value is the list of hostnames you excluded, and it never leaves the device.

No options page, no filter subscriptions, no counters, no Pro version. MIT licensed, source at https://github.com/omikuji/hakarasenai