Manifest V3 without the guesswork

The file the browser judges you by

A browser extension is installed or rejected on the strength of one JSON file. manifest.json decides which surfaces exist (popup, options, side panel, new tab, DevTools), what the extension may do, and which pages its content scripts touch. Get a match pattern wrong and the browser rejects the whole extension — not the pattern, the extension.

The manifest generator is a free, no-login form that assembles a Manifest V3 file from the same vocabulary Nodlume uses to scaffold whole extension projects.

Permissions with reasons

Every permission checkbox shows why you'd want it and what install-time warning it triggers. That's a principle, not a nicety: a permission surface where boxes tick themselves with no argument is how extensions end up over-privileged. Implied permissions are handled for you — pick the side panel surface and the sidePanel permission follows.

Validated, never repaired

Match patterns are checked as you add them, against the real grammar. An invalid pattern shows the reason and is not added — silently "fixing" *://example.com into something plausible would ship a pattern you never wrote. An overly-broad pattern like <all_urls> is accepted with a caution, because sometimes you mean it, and you should know when you do.

There's also a standalone match pattern validator on the page — paste a pattern, get an instant verdict with the reason.

From manifest to project

The output is a clean, pretty-printed manifest.json — popup on by default, because an extension with no surface is one nobody can open. When you want more than the manifest, Nodlume's structure painter sketches the surfaces themselves, and the full workspace scaffolds the entire MV3 project: views, a generated hash router, a background service worker, content scripts, and cross-browser code on webextension-polyfill.