webmanifest

A web manifest, formally the Web App Manifest, is a JSON file that provides metadata about a web application so it can be installed and launched like a native app. It is especially important for Progressive Web Apps (PWAs) and helps define how the app should appear and behave when added to a home screen or app launcher.

The manifest is linked from an HTML document using a link element with rel="manifest", for example href="/manifest.webmanifest". While commonly named manifest.webmanifest or manifest.json, the file is a JSON document served with an appropriate content type such as application/manifest+json. The manifest itself is not a requirement for a PWA, but it enables installation, launch behavior, and a cohesive branding and user experience.

A manifest contains a JSON object with various fields. Essential ones include name and short_name (display text for the app), start_url (the URL to open when launched), display (such as standalone or fullscreen), scope (navigation scope), background_color and theme_color (branding for splash and UI), and icons (an array of icon objects with src, sizes, and type). Additional fields may specify orientation, description, related_applications, and related preferences.

Browsers use the manifest to present install prompts, generate icons, and configure the launch experience. It complements service workers by providing the installable app metadata but does not itself implement offline behavior.

Validation and support vary by browser. Tools like Lighthouse and manifest validators can help check structure and fields. Proper hosting and correct MIME types are important for reliable interpretation.