Free Web Manifest Checker

A broken manifest silently kills PWA installability — and browsers won't let a page fetch another site's manifest to check it. NToolHub's Web Manifest Checker takes the working approach: paste your manifest JSON and get a real 10-point validation covering installability requirements, icons, colors and best practices.

ℹ️
Note: browsers won’t let a page fetch another site’s manifest.webmanifest (CORS). Instead, paste your manifest JSON below — open view-source: on your manifest URL or copy it from DevTools → Application → Manifest.
Private by design. Only the JSON you paste is analyzed, entirely in your browser — nothing is fetched or uploaded.

How to Use the Web Manifest Checker

  1. Copy your manifest JSON (DevTools → Application → Manifest → copy).
  2. Paste it into the box and click Validate Manifest.
  3. Fix any red items — name, start_url and icons are required.
  4. Add the amber recommendations (512px + maskable icon) for full installability.

Features

Paste manifest JSON for instant validation of name/short_name, start_url, display mode, icons array, 192px/512px/maskable icon requirements, theme_color and background_color formats — with a scored pass/warn/fail report.

Benefits & Use Cases

You catch the exact issues blocking the install prompt (usually a missing 512px or maskable icon) before users do — with specific, fixable findings instead of a vague 'not installable'.

Tips

Always include 192px and 512px icons plus a maskable one, validate JSON syntax first (one trailing comma breaks everything), and re-check after every manifest edit.

Frequently Asked Questions

Why do I paste the JSON instead of entering a URL?

Browsers block pages from fetching other sites' manifests via CORS. Pasting from DevTools (Application → Manifest) takes seconds and validates your actual file.

What makes a PWA installable?

A valid manifest with name, start_url, display mode, 192px+ and 512px+ icons, served over HTTPS with a registered service worker.

What's a maskable icon?

An icon with safe padding designed for Android adaptive-icon cropping ("purpose": "maskable"). Without it, launchers may cut off your logo.

My JSON won't parse — what now?

Trailing commas, comments and single quotes are the usual culprits — JSON allows none of them. Paste into a JSON validator, fix syntax, then re-run.

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