Guide
Structured Data Validation: Common Errors
The errors casino and sportsbook sites hit most are JSON syntax mistakes, misspelled type names, missing required properties, relative URLs and malformed dates. A JSON parser, the Schema Markup Validator and Google's Rich Results Test each catch different ones, and knowing which tool flagged an error tells you how to fix it.
Which tool checks what
| Tool | Question it answers | What it does not do |
|---|---|---|
| A JSON syntax check, such as the SchemaReel workbench | Does the markup parse, and are basic properties present? | Certify Google eligibility |
| Schema Markup Validator (validator.schema.org) | Is Schema.org vocabulary used "in widely understood ways"? | Check "the information needs of specific services" |
| Google Rich Results Test | Does the page meet the technical requirements of Google Search features? | Promise that a feature will appear |
The Schema Markup Validator launched in beta on May 21, 2021, as a general tool for Schema.org markup; Schema.org's announcement describes Google's Rich Results Test as the tool for Google's own features. Google's guidelines add that correct markup carries no guarantee: Google does not guarantee that structured data will show up in results, even when it passes the Rich Results Test.
Errors and fixes
JSON syntax errors
The most common cause is a trailing comma after the last property, followed by single quotes and comments. JSON allows none of these. Fix the template that writes the markup; do not patch the output. The workbench points to the line and column of the first error.
Wrong script type
JSON-LD must sit in <script type="application/ld+json">. A plain <script> tag runs as JavaScript and fails.
Missing or wrong @context
Without "@context": "https://schema.org", terms do not map to Schema.org. Inside an @graph, one context at the top covers every node.
Unknown types
Type names are case sensitive and use US spelling: Organization, WebSite, BreadcrumbList. Organisation and Website are not Schema.org types.
Missing required properties
Google says items "that are missing required properties are not eligible for rich results." Each feature has its own list: a BreadcrumbList needs position, name and item; a Review needs author and reviewRating; an AggregateRating needs ratingValue and a count. Organization and Article have no required properties, only recommended ones.
Relative, http or empty URLs
Use absolute https URLs for url, logo, image, item and sameAs. Google also requires image URLs in structured data to be crawlable and indexable.
Dates without time zones
Google's Article documentation recommends time zone information and otherwise uses Googlebot's time zone. Write 2026-10-26T09:00:00+01:00, not 2026-10-26T09:00.
Breadcrumb gaps
Missing positions, positions out of order and missing item URLs on middle levels. See breadcrumb trails by template.
Markup that is not on the page
No validator catches this one. Google's guidelines forbid marking up content that is not visible, and it is the error most likely to lead to a manual action.
{
"@context": "https://schema.org",
"@type": "Article",
"headline": "How we settle bets on postponed matches",
"author": "Dana Hollis",
"datePublished": "2026-09-14T09:00",
"image": "http://northwake.example/media/help.png"
}Where errors come from on gambling sites
- Plugins with defaults. SEO plugins that add FAQPage, ratings or SearchAction to every page.
- Shared templates across brands. One brand's logo or name hard-coded in a template used by another brand.
- Market editions. Copies of a template that drift apart over time.
- Content teams and markup out of sync. A visible date or author changes; the markup does not.
After the fix
Retest the page with the URL, not pasted code, so you see what Google sees. Then check the relevant rich result report in Search Console after Google recrawls the page. Validation reports can lag behind fixes by days or weeks, depending on crawling.
Questions
The Rich Results Test passes. Why no rich result?
Passing means the page meets technical requirements. Google says it does not guarantee that structured data will show up in results, and some features are limited by site type or no longer shown.
Should warnings be fixed?
Warnings usually mean a recommended property is missing. Add it when you have a true value; never invent one to clear a warning.
Is the SchemaReel workbench enough?
No. It is a learning tool for syntax and common rules. Use the Schema Markup Validator and Google's Rich Results Test before you publish.
Sources
How SchemaReel chooses, reads and dates its sources is set out on the data sources page.
- Google Search Central, General structured data guidelines, last updated July 10, 2026.
- Schema.org blog, Announcing Schema Markup Validator: validator.schema.org (beta), May 21, 2021.
- Google Search Central, Generate structured data with JavaScript, last updated December 10, 2025.
- Google Search Central, Article structured data, last updated September 8, 2026.
- Google Search Central, Breadcrumb structured data, last updated September 8, 2026.