Introducing HTTP File Generator: Generate .http Files from OpenAPI Specifications

Testing a REST API is a daily task. Postman and Insomnia are popular, but a plain-text .http file does the same job and lives in the repository, next to the code it calls. Visual Studio, Rider and the REST Client extension for VS Code all run it.

HTTP File Generator writes those files for you. You upload an OpenAPI specification, pick the endpoints you need, preview the result and download a ZIP archive. Everything runs in your browser: the specification never leaves your machine.

What is a .http file?

A .http file holds one or more HTTP requests, separated by ###. Each request has a method, a URL, headers and an optional body. Lines that start with @ declare variables, which the requests reference with {{name}}:

@baseUrl = https://api.example.com
@token = your_token_here

### Get all products
GET {{baseUrl}}/products
Authorization: Bearer {{token}}

### Create a product
POST {{baseUrl}}/products
Authorization: Bearer {{token}}
Content-Type: application/json

{
  "name": "Widget",
  "price": 9.99
}

You can send these requests from Visual Studio, from Rider or from VS Code with the REST Client extension: open the file and click Send Request above a request.

Why generate them?

A specification can describe hundreds of endpoints. Writing a request for each one by hand is slow, and the hand-written copy drifts from the API. HTTP File Generator:

• parses the specification for you: OpenAPI 3.x in .json, .yaml or .yml, uploaded or loaded from a URL;
• shows a live preview that follows your selection;
• builds a ZIP archive with one .http file per tag, split by path, so the files mirror the structure of the API.

How to use it

Step 1: load the specification

Open HTTP File Generator and drop your specification on the upload area, or click Browse files. The URL tab loads a specification from a public address instead; the server that hosts it must allow cross-origin requests, because the browser fetches it directly.

The file is parsed and its $refs resolved in the browser with @apidevtools/swagger-parser. The specification is never sent to a server.

Step 2: select the endpoints

The selection screen lists the operations grouped by tag, with the method, the path and the summary of each one. You can:

• filter by HTTP method or by tag;
• search by keyword, with the list narrowing as you type;
• select or clear a whole tag, or every endpoint at once;
• expand an endpoint to inspect its parameters, request body, responses and referenced schemas.

The preview panel updates each time you toggle an endpoint.

Step 3: download

Click Download to get the ZIP archive, or Copy to put the preview on your clipboard.

Here is what the tool generates for two endpoints of the Swagger Petstore specification:

# Petstore v1.0.0
# Base URL: https://petstore3.swagger.io/api/v3

@baseUrl = https://petstore3.swagger.io/api/v3
@token = your_token_here

### Add a new pet to the store
POST https://petstore3.swagger.io/api/v3/pet
Authorization: Bearer {{token}}
Content-Type: application/json

{
  "id": 1,
  "name": "doggie",
  "status": "available",
  "photoUrls": [
    "photoUrls1",
    "photoUrls2"
  ]
}

### Find pet by ID
@petId = 1
GET https://petstore3.swagger.io/api/v3/pet/{{petId}}
Authorization: Bearer {{token}}

• The header declares the first server URL and a @token placeholder: replace your_token_here with a real token before you send anything.
• Path and query parameters become variables, with a default taken from the specification (example, default, the first enum value) or from the parameter's type.
• A JSON body is built from the schema's example, or from its properties when there is none.

The repository's format reference lists every rule.

Tech stack

The interface is available in English and French, with light, dark and system themes.

Running it locally

You need Node.js 20.9 or later, the minimum Next.js 16 supports:

git clone https://github.com/Blouppy/http-file-generator.git
cd http-file-generator
npm install
npm run dev

The development server listens on http://localhost:3000. npm test runs the unit tests and npm run lint the linter. For the end-to-end tests, download the browser once with npx playwright install chromium, then run npm run test:e2e: Playwright builds the application and starts it before the tests.

Conclusion

HTTP File Generator removes the chore of writing .http files by hand. Drop in a specification, choose the endpoints and get files you can commit next to your code.

The project is open source on GitHub: Blouppy/http-file-generator.

References

• OpenAPI Specification — the format the tool reads.
• Use .http files in Visual Studio — Microsoft Learn: syntax, variables and sending requests.
• HTTP Client in Rider — JetBrains: the same format in Rider.
• REST Client for VS Code — the extension that runs .http files in VS Code.
• Cross-Origin Resource Sharing (CORS) — MDN: why loading a specification from a URL needs the host's consent.
• Swagger Parser — parsing, validating and dereferencing the specification.
• JSZip — building the archive in the browser.
• Next.js App Router — the framework the application is built on.
• Blouppy/http-file-generator — the source code, with the generated format reference.