How to generate API documentation?

[JoeanAmier]

I’ve used Python’s FastAPI, which can automatically generate API docs. I want to know if Express can also automatically generate API documentation.

Just like this:

[KhaledSaeed18]

Express doesn’t have built-in automatic API documentation like FastAPI, but there is a package that can help generate docs with minimal manual effort: swagger-autogen, which can automatically generate Swagger documentation by analyzing your code.

• https://www.npmjs.com/package/swagger-autogen
• https://swagger-autogen.github.io/docs/

[wesleytodd]

I also really need to find some time to help get https://github.com/wesleytodd/express-openapi updated for v5. I have been so focused on express itsef that I just have not had time to help unblock that.

[Yasir-Rafique]

You definitely can get automatic API docs with Express, though it works a bit differently than FastAPI, which has Swagger UI out of the box.

In Express, there are two main approaches:

JSDoc-style annotations:
Packages like swagger-jsdoc with swagger-ui-express let you add OpenAPI definitions right in your route comments. This way, you can keep docs close to your code, and the Swagger UI updates as you go. Downside: you do have to keep comments in sync with your code.

Code scanning/generation:
swagger-autogen is great if you want to skip writing docs manually. It analyzes your code and generates the Swagger docs automatically. This is quick for prototypes, but you may need to tweak things for more complex validation or custom logic.

If you just want to get up and running quickly, swagger-autogen is probably the fastest path. For bigger or longer-term projects, I personally find JSDoc comments with Swagger UI to be more robust, since it is easier for teams to maintain and review alongside the code.

After adding either approach, you will get an interactive Swagger UI usually at /api-docs very similar to FastAPI’s experience where you can test endpoints right from the browser.

So, Express does not bundle docs like FastAPI, but you can get a similar “try it out” experience with just a little setup using community packages.