Extension developer tools

Free tools that run entirely in your browser. No signup, no uploads to a server, no tracking.

Manifest V3 Validator

Check a Chrome extension manifest.json for JSON errors, deprecated Manifest V2 keys, missing required fields, and risky permissions.

Extension Icon Generator

Upload a single square image and download every icon size Chrome extensions need (16, 32, 48, 128 px) generated in your browser.

Match Pattern Tester

Check whether a Chrome extension match pattern (for content scripts or host permissions) matches a given URL, with a plain-English explanation.

Store Listing Preview

Draft your Chrome Web Store title, summary, and description with live character-limit counters and a store-card preview.