Structured data

What it means

Structured data is a machine-readable description of a page in the schema.org vocabulary. It tells a search engine whether this is an organisation, a service, an article, a product, a question or a definition.

It is written into the page and invisible to visitors. The payoff is more accurate understanding of the content and eligibility for richer search results.

Structured data is neither meta tags nor keywords. A meta description is text for the snippet in results, whereas structured data describes relationships: who provides the service, where it is registered, which article belongs to which term. For SEO it is therefore a supplement that explains the content to the search engine, not a lever for choosing which queries the page appears for.

How it works in practice

For a company it makes sense to mark up the basics: the organisation itself, the services offered, frequently asked questions and expert articles. For a glossary, the individual definitions too.

The markup must match what the page actually shows. Where they diverge the engine ignores it and, at worst, treats it as manipulation.

Company details, meaning name, IČO, address and contacts, should read in structured data exactly as they do in the Commercial Register and in the site footer. When a client changes address or phone number, they must be updated everywhere at once; otherwise the search engine sees two different facts about one company and cannot tell which to trust.

What to watch out for

Structured data replaces neither content nor speed: without solid text and decent Core Web Vitals markup alone will not lift rankings. It is a complement, not a shortcut.

When moving to a new CMS or redesigning the site, structured data often disappears quietly, because a plugin that the new system lacks used to generate it. The site looks the same, but the rich result disappears and nobody knows why. After every major change it is worth running the pages through a validator again.