By Zach Wennstedt, founder of Eye To Ad Media · 2026-09-29
The most common schema markup mistakes are invalid JSON syntax, structured data that describes content not visible on the page, relative URLs and non-ISO dates, disconnected entities without @id links, self-serving review markup, and plugins that output duplicate or conflicting schema.
Schema markup is one of those things everyone agrees is important and almost nobody checks after it ships. Then a theme update breaks it, a plugin doubles it, and nobody notices for a year.
These are the mistakes we see most, roughly in order of how often we fix them.
1. The JSON does not parse
One trailing comma, one curly quote pasted from a word processor, one missing bracket, and search engines ignore the whole block. It is the most common problem and the easiest to catch. Paste your markup into our schema markup validator and it points to the line.
2. Markup describes things the page does not show
Google's structured data guidelines say markup should describe content that is visible to users. FAQ schema for questions that are not on the page, prices that are not shown, ratings that do not exist: at best ignored, at worst treated as spam.
3. Relative URLs and loose dates
Properties like url, image and logo should be absolute URLs. Dates should be ISO 8601, like 2026-09-29, not "last Tuesday" or "Sept 29."
4. Entities that never meet
A page has an Organization block, a WebPage block and a Service block, and none of them reference each other. Use @id to connect them: the Service is provided by the Organization, the WebPage is part of the WebSite. Our validator draws the graph so you can see floating nodes.
5. Reviewing yourself
Adding AggregateRating markup about your own business on your own site will not earn review stars in Google, which excludes self-serving reviews for local businesses and organizations. Show real reviews to people. Do not mark them up about yourself.
6. Three plugins, three versions of the truth
An SEO plugin outputs one Organization, the theme outputs another, a reviews widget outputs a third with a different name and phone number. Machines now have three conflicting answers. Pick one source of truth.
7. Generic types
"LocalBusiness" is fine. "Plumber," "Dentist" or "LegalService" is better. Use the most specific type that is accurate.
Want it engineered properly across your whole site instead of page by page? That is exactly what our technical SEO services cover.