JSON-LD is an easy-to-use JSON-based linked data format that defines the concept of context to specify the vocabulary for types and properties. Gmail supports JSON-LD data embedded in HTML documents with the @context of schema.org, as in the following example:

<script type="application/ld+json">
  "@context": "http://schema.org",
  "@type": "Person",
  "name": "John Doe",
  "jobTitle": "Graduate research assistant",
  "affiliation": "University of Dreams",
  "additionalName": "Johnny",
  "url": "http://www.example.com",
  "address": {
    "@type": "PostalAddress",
    "streetAddress": "1234 Peach Drive",
    "addressLocality": "Wonderland",
    "addressRegion": "Georgia"

The full specifications and requirements for the JSON-LD syntax are available on json-ld.org, and you can also use our Schema Validator tool to try out JSON-LD and debug your markup.