Structured data is a standardized way of describing what is on a page so that a machine can read it without guessing. It’s part of technical SEO, the work of making a site readable by search engines, and its purpose is specific: adding it can make a page eligible for a richer appearance in search results. It doesn’t make a page rank higher, and Google’s own documentation is careful about the difference.
In plain English
The difference between a letter and a form.
You could write: the workshop runs on the fourth, at the Rose Hotel, and tickets are $80. A person reads that and extracts three facts without effort. A machine has to infer that “the fourth” is a date, that the Rose Hotel is a venue, and that $80 is a price rather than a room number.
Or you fill in a form. Date. Venue. Price. Same facts, no inference required.
That’s all structured data is. And it carries the obvious constraint of any form: if the form says 80 and the letter says 120, you haven’t created a better description. You’ve created a discrepancy.
Why this matters for your site
The visible effect is the search result itself. A result that carries a star rating, a price, a cook time, an event date, or a set of breadcrumbs occupies more space and gives a searcher more to act on before they click.
Google’s documentation cites its own case studies with numbers attached: Rotten Tomatoes measured a 25% higher click-through rate on 100,000 pages with structured data compared to those without, and Nestlé measured an 82% higher click-through rate for pages appearing as rich results.
The less visible effect is that structured data also helps Google understand the page. Google says it uses what it finds to build its understanding of the content, and of the people, books, and companies described in the markup.
How it actually works
The format. Google supports three: JSON-LD, which it recommends, plus Microdata and RDFa. JSON-LD sits in a script block in the page’s code, separate from the visible markup, which is why it’s easier to generate and maintain than the alternatives.
The vocabulary. The types and properties come from schema.org, a shared vocabulary used across search engines rather than something Google invented alone.
What it can produce. These are the rich results, meaning search results with extra visual detail. Google’s gallery covers articles, breadcrumbs, courses, events, FAQs, job postings, local businesses, products, recipes, reviews, videos, and a long list of others.
Eligibility, not entitlement. Google’s wording is that implementing structured data makes your site eligible for these results, that the actual appearance may differ, and that you can preview most features with the Rich Results Test. Correct markup is a requirement, not a guarantee.
The rules that matter. Google’s general guidelines are short. Don’t block pages carrying structured data from being crawled or indexed. Keep the information current, since Google won’t show a rich result for time-sensitive content that is no longer relevant. Provide original content. Don’t mark up content that isn’t visible to readers: if the markup describes a performer, the body of the page must describe that same performer. And don’t mark up irrelevant or misleading content, fake reviews being the named example.
The consequence of breaking them. Google states that a structured data issue can result in a manual action, meaning a penalty applied by a human reviewer at Google. The scope is narrow and worth knowing precisely: the page loses eligibility for rich results, and it doesn’t affect how the page ranks in web search.
AI features. Google states there is no special markup required for its generative AI features, including AI Overviews, the generated summaries shown above results.
What this looks like in practice
A training company marks up its courses with prices and start dates. Six months later the prices change on the pages, because the pages are edited by the marketing team, while the markup is a static block nobody remembers exists.
Search results now advertise last year’s prices. Visitors arrive with an expectation the page contradicts in its first line, and the sales team spends the quarter explaining a discrepancy the website created.
The failure isn’t technical. The markup is valid and Google is displaying it correctly. It’s a process failure: markup that’s written by hand once will drift from a page that’s edited continuously.
What people usually get wrong
“Adding schema will improve our rankings.” Google frames it as eligibility for a richer appearance. The click-through gains are real. The position gains are not what’s being offered.
“Mark up the reviews we’re about to collect.” Google’s guidelines require markup to describe content visible on the page. Fake or unshown content risks the page’s rich result eligibility.
“We added it, so we’ll get stars.” Eligibility isn’t display. Google says appearance may differ and recommends previewing with the Rich Results Test.
“AI search needs its own schema.” Google says it doesn’t.
What you can do about it
Start with the types that describe what your business actually is. A local business, an organization, a product, an article, an event. Resist the urge to mark up everything.
Use JSON-LD, and generate it from the same data that renders the page. Markup maintained separately from the content it describes will eventually contradict it.
Run the Rich Results Test on one page of each template before rolling anything out, and again after any redesign.
Watch the Enhancements reports in Google Search Console, which flag errors across all pages using a given type rather than one at a time.
If rich results disappear, check the Manual Actions report before assuming a technical fault. That report distinguishes a markup penalty from a broken implementation, and the two need completely different responses.
Words you will hear
Structured data. A standardized, machine-readable description of a page’s contents.
Schema markup. The same thing, named after the schema.org vocabulary it uses.
JSON-LD. Google’s recommended format, written as a script block in the page code.
Schema.org. The shared vocabulary of types and properties that the markup draws on.
Rich Results Test. Google’s free tool for checking what a page is eligible to display.
Markup. Code that describes content rather than displaying it.
For rich result, SERP and text result, see What is a SERP? For crawler and index, see How search works.
