Structured data: describing a page in a way machines can read
Valid markup and correct markup are different things. Only one of them describes the page in front of the reader.
What structured data does
Structured data is a machine-readable description of what a page contains, added alongside the visible content. It does not change what the reader sees; it tells a parser that this number is a price, this text is a question, this date is when an event starts.
Its practical use is that search engines can display pages differently when they trust the description — and that trust depends entirely on the description being accurate.
Valid is not the same as correct
A validator checks syntax and required properties. It cannot check whether the marked-up rating exists on the page, whether the price is real or whether the question is one the page answers. Markup can pass validation perfectly and still be wrong.
Marking up content that is not visible to the reader is the single most common cause of trouble, and it is the one search engines' guidelines are most explicit about.
What goes wrong most
| Problem | Symptom | Fix |
|---|---|---|
| Markup does not match the page | Nothing appears, or it is removed | Mark up only what is visible |
| Required property missing | Validator error | Read the type's documentation |
| Wrong type chosen | Valid but useless | Match the type to the content |
| Markup on a template, not the item | Every page claims the same thing | Generate per page |
| Stale data | Prices or dates out of date | Generate from the same source as the page |
| Duplicate blocks | Conflicting descriptions | One description per entity |
A workable order
- Decide what the page really is: an article, a product, an event, a set of questions.
- Read the documentation for that type and note the required properties.
- Generate the markup from the same data that renders the page, so the two cannot drift apart.
- Validate a sample of pages, not one hand-built example.
- Check reports in the search engine's own tools after a few weeks.
- Re-check after template changes, which is when markup silently breaks.
Where it is not worth it
For a small site of ordinary text pages, elaborate markup rarely repays the effort. Describing the page and its author accurately is enough. The types that earn their keep are the ones that describe something with real structure: products, events, recipes, questions.