What are the most common errors in structured data testing?

Short answer: The most frequent errors are mismatches between visible content and schema, missing required fields, wrong type choice, invalid value formats, and mistaking a testing tool’s pass for live validation.

Common error patterns

• Content mismatch: information in the schema that is not visible on the page; it violates guidelines and costs trust.
• Missing required fields: offers on Product or author on Review; the rich result is lost.
• Wrong type: Product on a service page, or an ill-fitting LocalBusiness subtype.
• Format errors: dates not in ISO 8601, prices without currency, broken JSON-LD syntax.
• Relying on one tool: even when the rich results test passes, Search Console validity and guideline reports must be watched.

A solid testing routine

When schema comes from templates, test every variant rather than one sample page; validate on staging before release, then compare the Search Console validity report against the baseline after release.