Handling CORS for Express Deployed on Vercel Using vercel.json
Overview This is a memo on how to handle CORS for Express deployed on Vercel using vercel.json.
Background I implemented CORS handling for the program introduced in the following article.
The following was used as a reference.
https://vercel.com/guides/how-to-enable-cors
Method The solution is as follows. While there may be other approaches, adding headers resolved the issue.
https://github.com/nakamura196/dts-typescript/commit/4c28f66b2af68950656dcb812f3e941d1b9b5feb
{ "version": 2, "builds": [ { "src": "src/index.ts", "use": "@vercel/node" } ], "rewrites": [ { "source": "/api/dts(.*)", "destination": "/src/index.ts" } ], "redirects": [ { "source": "/", "destination": "/api/dts", "permanent": true } ], "headers": [ { "source": "/api/(.*)", "headers": [ { "key": "Access-Control-Allow-Credentials", "value": "true" }, { "key": "Access-Control-Allow-Origin", "value": "*" }, { "key": "Access-Control-Allow-Methods", "value": "GET,OPTIONS,PATCH,DELETE,POST,PUT" }, { "key": "Access-Control-Allow-Headers", "value": "X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version" } ] } ] } Summary I hope this serves as a helpful reference.
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April 24, 2025 · Updated: April 24, 2025 · 1 min · Nakamura
