Browser Extension Permissions Explained (in Plain English)

When you install an extension, your browser shows a permissions popup — and most people click "Add" without reading it. But those permissions define exactly what the extension can do to your data. Here's what the common ones mean, and which should make you pause.

The big one: access to "all your data on all websites"

In an extension's manifest this is <all_urls> or a host permission like *://*/*. It means the extension can read and modify the content of every page you visit — including what you type into forms, the contents of your webmail, and pages behind your logins. Some extensions genuinely need it: an ad blocker has to inspect every page to block ads everywhere. A coupon finder arguably does too. But a simple theme switcher or a calculator does not. The question is always: is this scope justified by what the extension does?

Permissions worth a second look

• tabs / webNavigation — see the URLs of pages you open and your navigation between them. Fine for a tab manager; suspicious for a wallpaper extension.
• webRequest / declarativeNetRequest — observe or modify your network traffic. Essential for ad/content blockers; a powerful capability anywhere else.
• cookies — read your cookies, which can include session tokens that keep you logged in.
• history — read your full browsing history.
• nativeMessaging — talk to a separate program installed on your computer, outside the browser sandbox.
• management — see and disable your other extensions.
• debugger — one of the most powerful; it can inspect and control pages at a low level. Very rarely justified.

Manifest V3 vs V2

Newer extensions use "Manifest V3", a model designed to be more restrictive and sandboxed than the older "Manifest V2" — for example, V3 limits how extensions can intercept network requests. It isn't a guarantee of safety, but an extension still stuck on V2 is worth a closer look, especially if it hasn't been updated recently.

"Optional" vs required permissions

Some extensions request optional permissions only when you use a specific feature, instead of demanding everything up front. That's a sign of a developer who respects least-privilege — asking for the minimum needed. It's a small but real trust signal.

How we use this

Permissions are objective facts: they're declared in the extension's manifest, which is public. That's why Permissions & Access is the heaviest pillar (25 of 100 points) in our safety score — and why every extension profile lists exactly which higher-risk permissions it requests, with the manifest as the source. Check any extension's permissions on its profile page, or look them up directly with our safety checker.