Access-Control-Allow headers
Access-Control-Allow response headers are HTTP response headers that specify which cross-origin origins, methods, or request headers a server permits under CORS.
Spring Security in Action, Second Edition
Access-Control-Allow-Origin is an HTTP response header that specifies which origins may access a resource through cross-origin requests.
- How it is used
- Controls which foreign origins may use browser responses from an application during cross-origin requests.
- How deep it goes
- Explains browser rejection, default Spring Security behavior, related headers, and preflight testing without detailing header configuration code.
- Examples
- Uses an XMLHttpRequest from localhost to test, an iframe scenario, and a MockMvc OPTIONS test with an example origin.
- What you can do after
- Diagnose/debug browser CORS failures and verify allowed origins and methods with an OPTIONS-based test.
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Build Financial Software with Generative AI (From Scratch)
Access-Control-Allow-Origin is an HTTP response header that specifies which origins may access a resource.
- How it is used
- Resolves cross-origin API access failures by restricting which frontend origins may receive resources.
- How deep it goes
- Defines the header and demonstrates server middleware configuration, while deferring broader CORS behavior beyond essential preflight handling.
- Examples
- Uses a localhost frontend calling a localhost health endpoint and configures FastAPI middleware for that origin.
- What you can do after
- Operate/configure a FastAPI API to permit a specific frontend origin and required HTTP methods.
Related concepts
- CORSconfigures · Cross-Origin Resource Sharing (CORS) is a web standard that uses HTTP headers to let servers specify which origins may access their resources through browsers.
- access-control-allow-methodsconfigures · Access-Control-Allow-Methods is an HTTP response header specifying which HTTP methods are permitted in a cross-origin request.
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