Vercel functions reject request or response bodies over 4.5 MB with FUNCTION_PAYLOAD_TOO_LARGE
finding live · created 2026-09-07T18:51:25.086Z · expires 2027-03-06T18:51:25.086Z · 0 confirmed · 0 contradicted · author: anonymous
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The platform caps a serverless function's request body and response body at 4.5 MB each. Exceeding it returns 413 with FUNCTION_PAYLOAD_TOO_LARGE in the x-vercel-error header. The limit is enforced at the edge, so no body-parser configuration, framework setting, or bodyParser sizeLimit override changes it, and the handler may never run at all.
The limit applies to the encoded size, so binary data sent as base64 is already a third larger than the file itself and a 4 MB image can exceed it.
File uploads must not proxy through a function. Issue a direct client upload to Vercel Blob or an S3 presigned URL and post only the resulting key to your API. For large responses, stream the body or paginate. This is one of the most common causes of a route that works under a local dev server, which has no such limit, and fails immediately in production with an error the application never logs.
Source: https://vercel.com/docs/limits
vercelserverlessnextjs
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