Media type / application
application/manifest+json
The web app manifest: name, icons, theme colour, and display mode that make a site installable as a progressive web app.
Served inline: Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
Browser behaviour
Downloads
Charset
charset ignored
Compression
Compress in transit
Send it like this
Content-Type: application/manifest+jsonThe format defines its own encoding, so no charset parameter is registered for this type. Sending one is harmless, but receivers are required to ignore it — it is not doing what people think it does.
Handling verdict
Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
The format defines its own encoding, so no charset parameter is registered for this type. Sending one is harmless, but receivers are required to ignore it — it is not doing what people think it does.
The payload is text-like or otherwise repetitive, so gzip or Brotli removes real bytes. Enable it at the server or CDN.
Registered with IANA through a public review process, so the name is stable and every implementation can rely on it meaning the same thing.
Anatomy of the name
RFC 6838Top-level type
application
Application
Subtype
manifest+json
Registered in the standards tree.
Structured syntax
+json
Any client that can parse JSON can read the payload, even without understanding this specific type.
Parameters
none
Beyond the charset rule above, this type defines no parameters of its own.
What trips people up
1 note- Fetched without credentials by default, so a manifest behind auth silently fails to load.
Response headers
Content-Type: application/manifest+json
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.webmanifest"
Vary: Accept-Encodingnosniff stops the browser second-guessing the type you declared, which is what makes the rest of this reliable. Content-Disposition: attachment names the saved file and removes any doubt about rendering.
Server configuration
extension mappingnginx
types {
application/manifest+json webmanifest;
}Apache
AddType application/manifest+json .webmanifestCaddy
@type path *.webmanifest
header @type Content-Type "application/manifest+json"Extensions and other spellings
declaredFile extensions
File signature
No fixed signature — this format has no reliable magic number, so identify it by parsing rather than by the first few bytes.