JSON-LD vs Microdata vs RDFa: which format in 2026?

JSON-LD, no contest. Recommended by Google, Bing and Apple, most LLM-readable, easiest to maintain. Microdata and RDFa are legacy: migrate if you still carry them.

JSON-LD vs Microdata vs RDFa: which format in 2026, in 2026?

Three formats have coexisted since 2010. Microdata (HTML attributes itemscope, itemtype, itemprop) is the ancestor, heavy and intertwined with markup. RDFa (property, typeof) is more academic, scarcely adopted outside research. JSON-LD, created in 2014 by W3C, isolates the markup in a <script type="application/ld+json"> block separate from HTML, cleaner, more testable, more readable.

The LLM-specific advantage

"For LLMs, JSON-LD has a structural advantage: it can be extracted as a single block without parsing the surrounding HTML," explains Lorenzo Eeman, founder of PROEMA. An agent can fetch + JSON.parse and grab the full semantics in two operations. Microdata forces a full DOM parse, costlier and more fragile. Google publicly reaffirmed its preference for JSON-LD in 2025 in its Search Central documentation: « Google generally recommends JSON-LD for structured data if your site's setup allows it » (developers.google.com/search/docs/appearance/structured-data/intro-structured-data). Microsoft Bing and Apple align that recommendation for Copilot and Apple Intelligence. RDFa, effectively dead in technical marketing, still appears in academic and library contexts, irrelevant for B2B GEO.

Migration and common audit mistakes

PROEMA recommends JSON-LD for 100% of new sites and priority migration for legacy. Validation tools, in this order: Google Rich Results Test (official Google), Schema Markup Validator (official schema.org), json-ld.org/playground (visualisation). Common audit finding: legacy Microdata coexisting with JSON-LD with divergent values, the LLM picks one, sometimes wrong, and confidence drops. One source of truth per page. Other trap: generating JSON-LD server-side without validating types, a mistyped @type ("Articel") renders the block invisible. Validation at every deploy is non-negotiable.