# Develop REST APIs using OpenAPI in API Gateway
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You can use API Gateway to import a REST API from an external definition file into API Gateway. Currently, API Gateway supports [OpenAPI v2.0](https://github.com/OAI/OpenAPI-Specification/blob/main/versions/2.0.md) and [OpenAPI v3.0](https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.1.md) definition files, with exceptions listed in [Amazon API Gateway important notes for REST APIs](api-gateway-known-issues.md#api-gateway-known-issues-rest-apis). You can update an API by overwriting it with a new definition, or you can merge a definition with an existing API. You specify the options by using a `mode` query parameter in the request URL. 

For a tutorial on using the Import API feature from the API Gateway console, see [Tutorial: Create a REST API by importing an example](api-gateway-create-api-from-example.md).

**Topics**
+ [Import an edge-optimized API into API Gateway](import-edge-optimized-api.md)
+ [Import a Regional API into API Gateway](import-export-api-endpoints.md)
+ [Import an OpenAPI file to update an existing API definition](api-gateway-import-api-update.md)
+ [Set the OpenAPI `basePath` property](api-gateway-import-api-basePath.md)
+ [AWS variables for OpenAPI import](import-api-aws-variables.md)
+ [Errors and warnings from importing your API into API Gateway](api-gateway-import-api-errors-warnings.md)
+ [Export a REST API from API Gateway](api-gateway-export-api.md)