Can I import an existing OpenAPI or Swagger file?

Yes. You can import an existing OpenAPI or Swagger JSON specification using the Import Spec feature. The builder will parse the file and populate the editor automatically.

What formats does this OpenAPI Builder export?

This tool exports OpenAPI specifications in both JSON and YAML formats, fully compatible with Swagger UI, Postman, Redoc, and API gateways.

When should I use this OpenAPI Builder instead of a Swagger Viewer?

Use this OpenAPI Builder when you need to create or modify an API specification. If you already have a completed OpenAPI or Swagger file and only want to view or explore it, a Swagger Viewer is more appropriate.

OpenAPI & Swagger Builder – Create API Documentation Online (Free)

OpenAPI Spec Builder

API Information

API Title

Description

Version

Format

Servers

Endpoints (Paths)

Security Schemes

Danger Zone: This will clear all your progress and reset the editor to defaults.

Documentation

Specification Code

When to Use This OpenAPI Builder

Create a new OpenAPI or Swagger specification from scratch
Generate API documentation without writing JSON or YAML manually
Prototype REST APIs before backend implementation
Produce Swagger files for Swagger UI, Postman, or API gateways

Start Designing

When to Use a Swagger Viewer Instead

You already have an OpenAPI or Swagger file
You want to view or test an existing API specification
You need an interactive Swagger UI to explore endpoints

Swagger Viewer ReDoc Viewer

Create OpenAPI & Swagger Specifications Online

Creating accurate, standard-compliant API documentation is critical for modern software development. Our OpenAPI Builder (also known as a Swagger Editor Online) allows you to build comprehensive API specifications without touching a single line of JSON or YAML. Whether you're a frontend developer mocking a backend or a backend engineer documenting a REST API, this tool simplifies the process through a clean, form-based interface.

Key Features of the Online OpenAPI Editor

No-Code Interface: Define endpoints, methods, and parameters via simple inputs.
Real-Time Swagger UI: See exactly how your documentation will look to users as you build it.
Dual Export: Generate standard-compliant JSON or YAML files with one click.
OpenAPI 3.0 Support: Built on the latest standards for maximum compatibility with modern tools.
Standards-Compliant Output: Generates valid OpenAPI 3.x specifications
Compatible Everywhere: Works with Swagger UI, Postman, Redoc, and API gateways
Privacy First: Your API design stays in your browser. No data is sent to our servers.

How to Create a Swagger Specification Step-by-Step

Define API Meta Info: Start by giving your API a title, version, and a helpful description.
Configure Servers: Add your production and staging URLs so users can test the API.
Add Endpoints: Create paths like /users or /login and choose the appropriate HTTP methods (GET, POST, etc.).
Define Parameters: Add query strings, path variables, or headers that your API expects.
Provide Request Samples: For POST/PUT requests, paste a JSON sample of the expected request body.
Preview & Export: Switch to the "Code" tab to copy your YAML/JSON or download it for your project.

Example Use Case

If you need to create an OpenAPI specification for a REST API with endpoints like /users or /orders, this builder allows you to define methods, parameters, and request bodies and instantly generate Swagger JSON or YAML.

How This Compares to Other API Documentation Tools

This OpenAPI Builder focuses on creating OpenAPI and Swagger specifications using a structured, no-code form interface. Traditional tools like Swagger Editor are designed primarily for manual YAML or JSON editing, which can be error-prone for beginners. Tools such as Redocly excel at rendering and publishing API documentation, but they assume you already have a valid OpenAPI file. Meanwhile, Postman focuses on API testing and collaboration, with OpenAPI support as part of a broader workflow. This builder fills the gap by helping developers generate a clean, standards-compliant OpenAPI specification from scratch—before testing, publishing, or sharing it with other tools.

Frequently Asked Questions

Is this OpenAPI Builder free?

Yes. This OpenAPI Builder is completely free, runs entirely in the browser, and does not require signup or account creation.

What is the difference between Swagger and OpenAPI?

OpenAPI is the specification itself (the standard), while Swagger is a suite of tools (like Swagger UI) used to implement that specification. This builder supports the OpenAPI 3.0 standard.

Can I import an existing file?

Yes! Use the "Import Spec" button at the top of the editor. Currently, this tool is optimized for building and refining specifications. If you want to view an existing file without editing, we recommend using our Swagger Viewer.

OpenAPI & Swagger Specification Builder — Create API Documentation Online