What does Syntax errors in items of unknown type mean in the Rich Results Test?

Definition: “Syntax errors in items of unknown type” is a Rich Results Test section for parser errors that stop the tool before it can determine the rich result type. The section identifies malformed or incorrectly typed structured data that the test cannot associate with a specific rich result type.

Key facts

• Google says the section appears when an error halts the parser before it can determine the rich result type in the Rich Results Test help.
• The help page lists JSON-LD, RDFa, and Microdata as the structured data formats supported by the test.
• Google’s structured data introduction says the Rich Results Test validates structured data and can preview a feature in some cases.
• Google’s general structured data guidelines say the test and the URL Inspection tool catch most technical errors.

Why does the test show this section?

The label describes a parser stage. The Rich Results Test found structured data, but an error prevented it from reading far enough to assign the item a rich result type. Google’s help page says the test lists found items, including items that are good, have warnings or errors, or are unparseable. It also says that an error description can open the code explorer at the corresponding location in the rendered source code.

The failure can happen before Google evaluates the requirements for a type such as Recipe or Product. The message therefore points to syntax or data-shape repair. It is separate from a missing required property on an item whose type the tool has already identified.

Which parser failures can cause it?

Google lists an invalid JSON document when the JSON has a top-level syntax error. It also lists an incorrect value type, such as a string where a number or array is expected. Other entries cover a missing colon between a field and value, a missing comma or closing brace, an incomplete array, and a property or value whose start and end cannot be found.

String and Unicode problems have their own entries. The list includes an empty escape sequence, a bad escape sequence, a truncated Unicode character, an invalid Unicode character, and malformed Unicode escapes. It also includes duplicate unique properties, an invalid top-level JSON-LD element, and an itemref attribute that points to a nonexistent identifier.

For example, the help page shows a bad escape sequence in a string:

"description" : "Some \q unknown sequence"

The same page shows that two definitions of a unique property, such as two @context values, can produce a duplicate unique property error. The exact message tells you which part of the parser needs attention.

How should you fix and check it?

Open the individual error in the test, then use its code explorer location in rendered source. Repair the reported JSON punctuation, value type, escape, Unicode sequence, duplicate property, top-level element, or itemref. If the input is a URL, Google requires page resources to be accessible to an anonymous user, and the test lets you choose a smartphone or desktop user agent. If the input is a snippet, choose Code, paste the markup, and rerun the test after each edit.

Google Search supports three structured data formats, and its introduction recommends JSON-LD when the site setup allows it because it is easier to implement and maintain at scale. The general guidelines state that structured data pages should not be blocked to Googlebot by robots.txt, noindex, or another access control method. A parser-clean item still needs the required properties and the feature-specific guidance for its type.

Related terms

• Structured data
• JSON-LD
• JavaScript rendering and AI crawlers

FAQ

Does this message identify the rich result type?

No. Google defines the section as the result of an error that stops the parser before the rich result type can be determined. Fix the listed parser error first, then rerun the test to see whether the item is identified.

Is an unknown type the same as an unsupported type?

The help page describes this section in terms of parser failure. It does not document the label as a statement that a schema.org type is unsupported.

Can a valid parser result still have an error?

Yes. Google’s guidelines separately require the properties for a specific rich result type and state that items missing required properties are not eligible for rich results. The parser section concerns reading the item; type requirements are checked after the item can be identified.

Sources

1. Google Search Central, “Rich Results Test”, undated
2. Google Search Central, “Introduction to structured data markup in Google Search”, 10 December 2025
3. Google Search Central, “General structured data guidelines”, 10 July 2026

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