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maxLength JSON Schema Keyword

Use maxLength to limit a string to a maximum number of Unicode characters.

String

Schema template

Try in Validator

JSON Schema

{
  "type": "string",
  "maxLength": 12
}

Valid example JSON

"short-name"

Invalid example JSON

"this-name-is-too-long"

Fields

FieldTypeRequiredDescription
maxLengthintegerYesThe inclusive maximum string length. Use this to protect storage, UI layout, and downstream systems.

How to use this schema

Use maxLength for usernames, labels, slugs, titles, and free-text fields that must fit product or database limits.

Version support and combinations

This keyword or pattern is commonly supported across modern JSON Schema workflows. Check your validator for Draft-04, Draft-07, 2019-09, and 2020-12 behavior before relying on newer composition or conditional features.

Common combination: pair this reference with type, required, and properties so validation errors are specific enough for API clients and form users.

Batch validation seed

Want to validate JSON Schema in bulk? Toolumina Pro can grow into batch validation for 100+ files, saved schemas, and repeatable API contract checks.

Related reference pages

minLength JSON Schema KeywordUse minLength to require a string to contain at least a minimum number of Unicode characters.pattern JSON Schema KeywordUse pattern to require a string to match a regular expression, such as an internal code, slug, SKU, or constrained identifier.type JSON Schema KeywordUse type to require a JSON value to be a string, number, integer, boolean, object, array, or null before other rules are evaluated.