application/ld+json
applicationThe MIME type for JSON-LD (Linked Data) documents. Used by Google for structured data in HTML pages (inside <script type='application/ld+json'> tags) for rich search results. Also used by ActivityPub for Fediverse federation. The +json suffix indicates the document is parseable as JSON.
Details
application/ld+json is defined by the W3C JSON-LD specification. The +json suffix follows RFC 6838 structured syntax convention – the content is valid JSON and also carries semantic linked data meaning.
Google structured data: Google's primary supported format for rich results (schema.org markup). Added to HTML pages as: <script type="application/ld+json"> { "@context": "https://schema.org", "@type": "Article", ... } </script>
ActivityPub: the Fediverse federation protocol uses application/ld+json with an ActivityStreams @context for actor documents and activities.
Parsing: any JSON parser can read the content; a JSON-LD processor additionally understands the @context semantics.
Common use
Google structured data in HTML, ActivityPub federation, semantic web APIs