# CORS Error when Sending POST requests to Express Backend

**URL:** <https://community.firebasestudio.dev/t/cors-error-when-sending-post-requests-to-express-backend/6246>\
**Category:** General\
**Created:** [October 15, 2024, 4:48am UTC](https://community.firebasestudio.dev/t/cors-error-when-sending-post-requests-to-express-backend/6246 "2024-10-15T04:48:19Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![kirupa](https://sea2.discourse-cdn.com/flex002/user_avatar/community.firebasestudio.dev/kirupa/32/4_2.png) [@kirupa](https://community.firebasestudio.dev/u/kirupa)\
**Post date:** [October 15, 2024, 4:49am UTC](https://community.firebasestudio.dev/t/cors-error-when-sending-post-requests-to-express-backend/6246/2 "2024-10-15T04:49:36Z")

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Are you running into this issue by any chance?

> [@Early preview of public ports!](https://community.firebasestudio.dev/t/early-preview-of-public-ports/1911/17):
>
> Found the problem! Thanks so much for helping us identify it. In short, one of our proxies is removing CORS headers (e.g. Access-Control-Allow-Origin) in the HTTP response for the browser’s OPTIONS request (aka “preflight”, which are used for POST requests). I haven’t found a good workaround yet, but we’ll follow up in [the bug you filed](https://issuetracker.google.com/issues/369331504) (thank you!). Hopefully this is something we can resolve shortly. EDIT: I updated the bug title and added repro steps, will now follow up with our infra teams …

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_[View the full topic](https://community.firebasestudio.dev/t/cors-error-when-sending-post-requests-to-express-backend/6246)._