JSON-LD
JSON-LD is the structured data format Google recommends. It sits in a script block in the page head, separate from the visible markup, which makes it far easier to add and maintain than inline formats such as Microdata or RDFa.
Why it matters for your rankings
JSON-LD won because it decouples the machine-readable description of a page from its HTML. You can change your entire front-end design without breaking your structured data, which is not true of Microdata.
It is also the format most easily consumed by AI answer engines, which increasingly rely on structured data to establish facts about businesses, products and articles. The most common implementation error is drift: the markup says one price, the visible page says another, because they are maintained by different systems. Google treats mismatches between markup and visible content as a guidelines violation, and the penalty is losing rich results entirely, usually without a clear explanation of why.
How to check it on your site
Validate every template
Run one URL per page type through Google's Rich Results Test and the Schema.org validator. They catch different problems.
Check for content mismatch
Compare prices, ratings, availability and dates in the markup against what the page actually displays.
Watch for duplicate blocks
Plugins and themes frequently each inject their own schema, producing conflicting Organization or Article entries on the same page.
Monitor Search Console enhancements
The Enhancements section reports structured data errors Google found across the whole site.