Technique · schema.org · JSON‑LD · Microdata · Open Graph

Structured data, JSON‑LD and rich snippets

Structured data is information about a page written in a standardised vocabulary (schema.org) that a machine can read without guessing: "this is a product, it costs 199 zł, it is in stock, it is rated 4.7". Search engines show it as rich snippets (enhanced results with price, stars, FAQ, breadcrumbs), AI assistants quote it as fact, and screen readers and other tools rely on the same idea — explicit structure instead of appearance. The act does not require it. But a page with good structure for people usually has it for machines too — and vice versa.

Three formats, one vocabulary

Plus Open Graph (og:title, og:image…) and Twitter Cards — not schema.org, but the same goal: a link preview in messengers and social media. This site has both JSON‑LD and Open Graph — view the source.

Example: a product in a shop

<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Lumen 7 e‑reader",
  "image": ["https://shop.example/img/lumen-7.jpg"],
  "description": "A 7\" e‑reader with front light and text‑to‑speech.",
  "sku": "LUM-7",
  "brand": { "@type": "Brand", "name": "Lumen" },
  "offers": {
    "@type": "Offer",
    "url": "https://shop.example/lumen-7",
    "priceCurrency": "PLN",
    "price": "699.00",
    "availability": "https://schema.org/InStock",
    "hasMerchantReturnPolicy": { "@type": "MerchantReturnPolicy",
      "returnPolicyCategory": "https://schema.org/MerchantReturnFiniteReturnWindow",
      "merchantReturnDays": 14 }
  },
  "aggregateRating": { "@type": "AggregateRating", "ratingValue": "4.7", "reviewCount": "128" },
  "accessibilityFeature": ["readingOrder", "textToSpeech"],
  "accessibilitySummary": "Voice‑operated menu; Polish text‑to‑speech."
}
</script>

The last two fields are no accident: schema.org has the properties accessibilityFeature, accessibilityHazard, accessibilityControl and accessibilitySummary. For products covered by the act (e‑readers, computers, terminals) this is a ready‑made place for the accessibility information that art. 18(1) requires a shop to provide — readable by the customer and by the search engine.

Types worth having

The rules that decide whether it works

1. The data must match what is shown

   Google penalises ratings that are not on the page, prices other than the visible ones, FAQ hidden from the user. It is the same rule as in accessibility: structure describes content, it does not replace it.

2. One main object per page

   A product page is one Product; a product list is an ItemList with links, not 40 full products.

3. Valid JSON

   One comma too many and the whole block is ignored without a message. Our checker parses every JSON‑LD block and reports the unparseable ones (rule pad-structured-data).

4. Test

   Google's Rich Results Test and the Schema Markup Validator (validator.schema.org) show what was read and which fields are missing for a rich result.

5. Don't invent fields

   The schema.org vocabulary is closed; unknown properties are ignored. When something is missing, use additionalProperty.

What this has to do with the act

Directly — nothing: neither the EAA, nor the Polish act, nor WCAG require schema.org. Indirectly — a lot:

• The same discipline. A page where the price is text (not an image), breadcrumbs are a list, the FAQ is headings and paragraphs, and the product has a name, description and photo with an alternative — is accessible and ready for structured data. A page built of images and divs is neither.
• Product accessibility information (art. 18(1)) has ready fields in schema.org that comparison sites and search engines understand.
• Statement and terms. WebPage types with accessibilitySummary and an "Accessibility" page linked from Organization make the art. 32 information easier to find — also for the authority.
• AI assistants increasingly answer questions about a shop from structured data and the llms.txt file. This site has both.

What the checker shows

In the page profile the report lists the schema.org types found (e.g. Organization, Product, BreadcrumbList), the number of blocks and any unparseable ones, and the e‑commerce signals detected from, among others, Product/Offer. A lack of structured data is marked as information, not as a breach — because it is not one.

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