Why it matters to a buyer
JSON-LD is worth knowing by name because it is the specific format Google recommends over the alternatives, microdata and RDFa, which require markup attributes scattered through the visible HTML and are easier to break during a redesign. For a buyer, a developer proposing microdata instead of JSON-LD without a strong reason is adding unnecessary fragility: JSON-LD can be generated, tested and updated as one clean block, independent of the page's visual template.
How it is measured or applied
A JSON-LD block is added as a script tag with type application/ld+json, describing the page's content using Schema.org vocabulary, such as Product, Article or Organization, with values that match what a visitor actually sees on the page. It is validated with Google's Rich Results Test and the Schema Markup Validator before launch, and monitored afterward through Search Console's enhancement reports, which show valid, warned and erroring items across the site so problems in a shared template are caught before they spread to every page that uses it.
Sources
- Introduction to structured data markup, Google Search Central
