Simeon Vincent dotproto

This information was retrieved and collated on 2026-08-26.

Columns

Affects

The Affects column refers to how many records can be removed by a given removal method. This provides a high-level way to scope

one - The removal method can only remove one record in a call.
multiple - The removal method can remove one or more records in a call. If the method can also be used to remove a single record, it is still classified as "multiple".

Recently I was looking for ways for WebExtensions to back up critical state. The contents of this gist are the very rough test extension I was using to explore options.

There are two main ways of interacting with this extension:

The extensin's options page (options.html) has tests for working with <input type="file">, File System Access, and storing file handles in IndexedDB.
The action context menu test ways to save files to disk using web APIs and the WebExtensions Downloads API.

Warning

File System Access tests may be destructive! Create a new temp directory to prevent accidetnally overwiting other files.

Setup

Copy the files in this gist into a temporary a local directory.
CD into temporary directory and start a local HTTP server. I used npx http-server --proxy http://localhost:8080?, but anything should work
In your borwser of choice, load the webext directory as a temporary extension.
NOTE: You may need to grant additional host permissions after installation.
If the extension didn't, open a new tab to http://localhost:8080
Inspect the page, select the Network tab, and make the console visible.
Reload the page.

When the page reloads, you should see a set of network requests that were blocked by the extension either in the Network tab directly or in the console.

This gist contains a WebExtension that tests how the browser that runs it handles ports host permission patterns.

Running tests

(optional) Create a new browser profile to ensure that this test runs in a clean environment.
Load this extension in your browser.
Start a debug session for the extension's background context.
(optional) Diable "debug" or "verbose" log messages
Check if your browser auto-upgrades HTTP requests to HTTPS by calling testHttpUpgrades() in the console. If you see a console message that says "Your browser auto-upgraded one or more HTTP requests to HTTPS!", consult the HTTPs Upgrades section below.

timeout() is a promise-based version of setTimeout() with AbortSignal support.

Save the files from this gist in a local directory.
Load that directory in Firefox as a temporary extension.
Visit https://example.com and open developer tools.
Click the "Open port" button and note the logged messages.
Click the "Send message" button and note the logged messages.
Wait ~30 seconds. Observe that a "Port disconnected!" message is logged.
Wait another 30 seconds as described in the issue (#36097).
Click "Open port" again.

Result: Could not reproduce the issue. The backgroudn starts up, recieves the connection request, and opens a port as expected.

This gist contains a browser extension that tests browser support for testing how onAuthRequired event handlers handle different resoultion patterns. It created in support of reviewing https://github.com/mdn/webextensions-examples/pull/564.

Test #	extraInfoSpec	Description	Chrome	Firefox
1	`blocking`	Synchronous object response	✅	✅
2	`blocking`	Synchronous Promise response with async resolution	❌	✅
3	`asyncBlocking`	Synchronous object response	❌	❌
4	`asyncBlocking`	Synchronous Promise response with async resolution	❌	❌
5	`asyncBlocking`	Async callback call with object	✅	✅

	export class PermissionCache {
	static areas = ["origins", "permissions", "data_collection"];

	origins = [];
	permissions = [];
	data_collection = [];
	ready;

	constructor () {
	this.ready = browser.permissions.getAll().then((grants) => {

	class Singleton {
	static #instances = new WeakMap();

	/**
	* @param {Boolean} useSharedThis Specifies whether or not `this` should be the singleton itself.
	* If `true`, the Singleton class' constructor will return the singleton associated with the current
	* prototype being instantiated. As a direct result, instance fields on the inherting class will be
	* re-set on the singleton every time the descendant class is instantiated. This may created
	* unnecessary and avoidable work. The main advantage of selecting `true` is that the sub-class does
	* not have to explicitly return the singleton, since class constructors implicitly return `this`.

	(async () => {

	const stores = await browser.cookies.getAllCookieStores();
	const store = stores.at(1);

	const exp = /(firefox\|mozilla).(org\|com\|auth0.com)/;
	const allCookies = await browser.cookies.getAll({storeId: s.id});
	console.log("All cookies:", allCookies);
	const filteredCookies = allCookies.filter(c => c.domain.match(exp));
	const removeCookies = filteredCookies.map(cookie => {