Comma decimal in ratingValue or price: an invalid number

What it means

A ratingValue or price property in this page's JSON-LD uses a comma as the decimal separator — for example "4,4" or "19,99". JSON requires a period (.) for decimals, so a comma-delimited value is parsed as a string, not a number. Google's structured-data parser rejects it and the associated rich result — a review star rating or product price — will not render.

Why it matters

JSON has one decimal format: the period (RFC 8259). A value like "4,4" is a string, semantically no different from "hello" to a JSON parser, so "ratingValue": "4,4" cannot be treated as a number and the review snippet fails to qualify. Google's Review Snippet documentation calls this out by name as a common error. The impact is real: star ratings are suppressed in the SERP (losing a CTR signal), Merchant Center integrations reading Offer.price fail to parse it, and it is a silent failure — the markup is valid JSON and throws no parse error, so teams often miss it. The cause is almost always locale-specific number formatting (German, French, Russian, and other markets where , is the decimal separator) applied to JSON-LD output that should always use period notation regardless of locale.

How to fix it

1. Search your JSON-LD templates and generation code for ratingValue and price output.
2. Format the number with a period decimal separator before writing it into JSON-LD.
3. Remove any locale-specific number-formatting functions applied to these fields.
4. Prefer emitting numeric values as bare JSON numbers (no quotes) to remove any format ambiguity — both a quoted string with a period and a bare number are acceptable to Google; a comma-delimited string is not.
5. Validate the corrected markup in Google's Rich Results Test.

When it's not a problem

False positives are near zero — a comma in a numeric ratingValue or price field is never valid notation, and there is no edge case where "4,4" is the correct way to express 4.4 in JSON-LD. A comma inside a different kind of value (a SKU or a title string) is not matched, because the check targets only numeric-looking ratingValue/price values.

How common is it?

7 audited sites in our corpus currently show this issue. The breakdowns below show which platforms, gatekeepers, verticals and countries are most exposed.