OpenAPI 3.1 Spec Validator
Paste your OpenAPI YAML or JSON to get instant validation with errors, warnings, and auto-fix suggestions. Supports OpenAPI 3.1, 3.0, and Swagger 2.0. Checks $ref resolution, operationIds, deprecated nullable patterns, and JSON Schema alignment.
Frequently Asked Questions
What is OpenAPI 3.1 and how does it differ from 3.0?▼
OpenAPI 3.1.0 (released February 2021) aligns fully with JSON Schema 2020-12, whereas 3.0 used a custom subset. Key differences: (1) nullable is replaced by type arrays like type: [string, null], (2) webhooks object added for async event definitions, (3) pathItems can be reused via $ref in paths, (4) schema composition (anyOf, oneOf, allOf) is more powerful, (5) info.license now supports SPDX expression identifiers.
What does the 'nullable: true' warning mean?▼
In OpenAPI 3.0, nullable: true was the way to allow null values for a field. In OpenAPI 3.1, this is removed in favor of the standard JSON Schema approach: use type: ['string', 'null'] (or any base type + 'null'). The validator flags nullable: true as a warning in 3.1 specs and suggests the correct replacement.
Why should every operation have an operationId?▼
operationId is used by SDK generators (openapi-generator, swagger-codegen), documentation tools, and API gateways to name methods and functions. Without it, generators create ugly names like 'getApiV1Users'. A good operationId is camelCase, unique across your spec, and describes the action: listUsers, createUser, getUserById.
Does this validator support YAML and JSON?▼
Yes. Paste your spec in either YAML or JSON format — the validator auto-detects the format. Both OpenAPI 3.1, 3.0, and Swagger 2.0 are supported, with upgrade suggestions when using older versions.
How does $ref validation work?▼
The validator resolves all internal $ref references (those starting with #/) and checks that the target path exists in the spec. External $refs (pointing to other files or URLs) are not resolved since this is a browser-based tool, but they are detected and reported.
What are auto-fix suggestions?▼
For each validation error or warning, the validator provides a concrete fix suggestion. For example: 'Missing info.version → Add version: 1.0.0', or 'nullable:true → Replace with type:["string","null"]'. Toggle 'Show fixes' in the results panel to see or hide them.
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Paste your OpenAPI 3.x spec (YAML or JSON) to validate structure, find missing required fields, detect duplicate paths, check for missing operationIds, and get errors and warnings with path references.
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