Vercel deploy errorVercel: “Serverless Function has exceeded the unzipped maximum size of 250 MB”

Why the function is too big, and the fix

1. 01

   One function bundle is over 250 MB uncompressed

   “the maximum uncompressed size is 250 MB including layers which are automatically used depending on runtimes.” Vercel, Vercel Functions Limits

   The limit counts everything the function ships with, uncompressed: your code, node_modules it uses and any file it reads. The error does not say which file is the problem, so measure first.

2. 02

   Measure which function and which files

   “VERCEL_ANALYZE_BUILD_OUTPUT environment variable with the value 1 and redeploy. The build logs then list each function's uncompressed size” Vercel, Vercel Functions Limits

   Add the environment variable VERCEL_ANALYZE_BUILD_OUTPUT with the value 1 in the project settings and redeploy. The build log then lists each function with its size and the largest files in it, so you know which package or folder to cut.

3. 03

   Heavy or duplicate packages

   “Duplicate copies of the same package also add size. Run npm ls <package> to see why a package is installed, and npm dedupe to remove duplicates.” Vercel, Vercel Functions Limits

   Some packages carry large binaries, such as headless browsers, image libraries or AI SDKs with native parts. Two versions of the same package double the cost. Run npm ls on the big ones to see who pulls them in, dedupe, and replace a heavy package with a lighter one or a hosted API where you can.

4. 04

   Files traced into the function by accident

   “Images, videos, or large JSON files that server code imports or reads are packaged with the function.” Vercel, Vercel Functions Limits

   An import or fs read with a path built at runtime can pull a whole folder into the bundle. Serve images, videos and large JSON from public or from storage, use fixed import paths, and exclude what the function never needs. In Next.js, list those paths under outputFileTracingExcludes in next.config.js.

   // next.config.js (Next.js 15 and later; on 14 it sits under experimental)
   // only exclude files the function never reads at runtime
   module.exports = {
     outputFileTracingExcludes: {
       '/api/*': ['./public/**/*', './data/large/**/*'],
     },
   };

Checked against the vendor’s docs on November 7, 2026: Vercel: Functions limits (bundle size, troubleshooting the 250 MB limit, large functions).

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