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Handle CORS issues in Fastapi

Donald Le
1 min readSep 12, 2021

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Photo by Tuyen Vo on Unsplash

When using REST API in front-end recently, I met an issue when front-end keep throwing error

network error when attempting to fetch resource.

this issue turns out to be a problem due to CORS.

Cross-Origin Resource Sharing (CORS) is an HTTP-header based mechanism that allows a server to indicate any origins  (domain, scheme, or port) other than its own from which a browser  should permit loading of resources. CORS also relies on a mechanism by  which browsers make a "preflight" request to the server hosting the  cross-origin resource, in order to check that the server will permit the  actual request. In that preflight, the browser sends headers that  indicate the HTTP method and headers that will be used in the actual  request.

So in order to get rid of CORS issues, we need to tell Fastapi to trust some origins and add middlewares :

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Donald Le
Donald Le

Written by Donald Le

A passionate automation engineer who strongly believes in “A man can do anything he wants if he puts in the work”.

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