# express-openapi-validator
> Automatically validate API requests and responses with OpenAPI 3 and Express.
Latest version **5.6.2** (published 2026-01-20) · MIT license · 0 weekly downloads
## Install
```sh
npm install express-openapi-validator
pnpm add express-openapi-validator
yarn add express-openapi-validator
bun add express-openapi-validator
```
## Health
**Score 60/100 (C)** — status: stable.
Positive: has types; no vulnerabilities; high maintenance score; high quality score.
Warnings: low downloads; no esm support.
## Facts
| | |
|---|---|
| Version | 5.6.2 |
| Published | 2026-01-20 |
| First published | 2019-03-25 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | CommonJS |
| Dependencies | 14 |
| Unpacked size | 428.4 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 1006 |
| Author | Carmine DiMascio |
| Maintainers | cdimascio |
| Keywords | openapi, openapi 3, expressjs, express, request validation, response validation, middleware, nodejs |
## Links
- npm: https://www.npmjs.com/package/express-openapi-validator
- Repository: https://github.com/cdimascio/express-openapi-validator
- Homepage: https://github.com/cdimascio/express-openapi-validator#readme
- Issues: https://github.com/cdimascio/express-openapi-validator/issues
- npm.io page: https://npm.io/package/express-openapi-validator
## Dependencies (14)
- [qs](https://npm.io/package/qs.md) ^6.14.1
- [ajv](https://npm.io/package/ajv.md) ^8.17.1
- [ono](https://npm.io/package/ono.md) ^7.1.3
- [multer](https://npm.io/package/multer.md) ^2.0.2
- [lodash.get](https://npm.io/package/lodash.get.md) ^4.4.2
- [ajv-formats](https://npm.io/package/ajv-formats.md) ^3.0.1
- [media-typer](https://npm.io/package/media-typer.md) ^1.1.0
- [ajv-draft-04](https://npm.io/package/ajv-draft-04.md) ^1.0.0
- [content-type](https://npm.io/package/content-type.md) ^1.0.5
- [@types/multer](https://npm.io/package/@types/multer.md) ^2.0.0
- [path-to-regexp](https://npm.io/package/path-to-regexp.md) ^8.3.0
- [lodash.clonedeep](https://npm.io/package/lodash.clonedeep.md) ^4.5.0
- [json-schema-traverse](https://npm.io/package/json-schema-traverse.md) ^1.0.0
- [@apidevtools/json-schema-ref-parser](https://npm.io/package/@apidevtools/json-schema-ref-parser.md) ^14.2.1
## Alternatives
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## Recent versions
- 5.6.2 (latest) — 2026-01-20
- 4.13.9 (v4-lts) — 2025-06-07
- 5.5.0-beta.2 (beta) — 2025-05-03
- 6.0.0-alpha.9 (alpha) — 2025-04-15
- 6.0.0-alpha.6 (alpha.6) — 2024-12-19
- 6.0.0-alpha.5 (alpha.5) — 2024-11-11
- 6.0.0-alpha.3 (alpha.3) — 2024-09-01
- 5.6.1 — 2026-01-17
- 5.6.0 — 2025-09-06
- 5.5.8 — 2025-07-27
- 5.5.7 — 2025-06-11
- 5.5.6 — 2025-06-07
- 5.5.5 — 2025-06-07
- 5.5.4 — 2025-06-07
- 5.5.3 — 2025-05-24
- … 295 more at https://npm.io/package/express-openapi-validator/versions
## README
# 🦋 express-openapi-validator
[](#) [](https://www.npmjs.com/package/express-openapi-validator) [](https://www.npmjs.com/package/express-openapi-validator) [](#contributors) [](https://coveralls.io/github/cdimascio/express-openapi-validator?branch=master) [](https://www.codacy.com/manual/cdimascio/express-openapi-validator?utm_source=github.com&utm_medium=referral&utm_content=cdimascio/express-openapi-validator&utm_campaign=Badge_Grade) [](https://gitter.im/cdimascio-oss/community) [](https://gitpod.io/#https://github.com/cdimascio/express-openapi-validator) [](https://cdimascio.github.io/express-openapi-validator-documentation/) [](#license)
**An OpenApi validator for ExpressJS** that automatically validates **API** _**requests**_ and _**responses**_ using an **OpenAPI 3** specification.
[🦋express-openapi-validator](https://github.com/cdimascio/express-openapi-validator) is an unopinionated library that integrates with new and existing API applications. express-openapi-validator lets you write code the way you want; it does not impose any coding convention or project layout. Simply, install the validator onto your express app, point it to your **OpenAPI 3.0.x** or **3.1.x** specification, then define and implement routes the way you prefer. See an [example](https://cdimascio.github.io/express-openapi-validator-documentation/guide-standard/).
**Features:**
- ✔️ request validation
- ✔️ response validation (json only)
- 👮 security validation / custom security functions
- 👽 3rd party / custom formats / custom data serialization-deserialization
- 🧵 optionally auto-map OpenAPI endpoints to Express handler functions
- ✂️ **\$ref** support; split specs over multiple files
- 🎈 file upload
- ✏️ OpenAPI 3.0.x and 3.1.x spec support
- ✨ Express 4 and 5 support
**Docs:**
- 📖 [documentation](https://cdimascio.github.io/express-openapi-validator-documentation/)
[](https://GitHub.com/cdimascio/express-openapi-validator/stargazers/) [](https://twitter.com/intent/tweet?text=Check%20out%20express-openapi-validator%20by%20%40CarmineDiMascio%20https%3A%2F%2Fgithub.com%2Fcdimascio%2Fexpress-openapi-validator%20%F0%9F%91%8D)
[Express 5](https://expressjs.com/en/5x/api.html) support available in `>=v5.5.0`!
[OAS 3.1](https://github.com/cdimascio/express-openapi-validator/pull/882) support available in `>=v5.4.0`!
[NestJS](https://github.com/cdimascio/express-openapi-validator/tree/master/examples/9-nestjs)
[Koa](https://github.com/cdimascio/express-openapi-validator/tree/lerna-fastify/packages/koa-openapi-validator) and [Fastify](https://github.com/cdimascio/express-openapi-validator/tree/lerna-fastify/packages/fastify-openapi-validator) now available! 🚀
## Install
```shell
npm install express-openapi-validator
```
## Usage
1. Require/import the openapi validator
```javascript
const OpenApiValidator = require('express-openapi-validator');
```
or
```javascript
import * as OpenApiValidator from 'express-openapi-validator';
```
2. Install the middleware
```javascript
app.use(
OpenApiValidator.middleware({
apiSpec: './openapi.yaml',
validateRequests: true, // (default)
validateResponses: true, // false by default
}),
);
```
3. Register an error handler
```javascript
app.use((err, req, res, next) => {
// format error
res.status(err.status || 500).json({
message: err.message,
errors: err.errors,
});
});
```
_**Important:** Ensure express is configured with all relevant body parsers. Body parser middleware functions must be specified prior to any validated routes. See an [example](#example-express-api-server)_.
## [Documentation](https://cdimascio.github.io/express-openapi-validator-documentation/)
See the [doc](https://cdimascio.github.io/express-openapi-validator-documentation/) for complete documenation
_deprecated_ [legacy doc](https://github.com/cdimascio/express-openapi-validator/wiki)
## License
[MIT](LICENSE)
---
_Source: https://npm.io/package/express-openapi-validator · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._