vercel edge function failed: 'Edge Function size exceeds 1 MB'

TL;DR

Vercel Edge Functions (including middleware) must stay under 1 MB. Heavy imports bundled into the edge entry push it over. Audit the edge bundle, trim or externalize heavy dependencies, and keep edge code to routing, auth checks, and rewrites.

The query

vercel edge function failed: 'Edge Function size exceeds 1 MB'

Use this when

• Deploy fails naming the edge function size limit.
• The failing entry is middleware.ts or an edge-runtime route.
• It worked until a dependency was added to edge code.

Not for

• Serverless (Node runtime) function size limits (different runtime, different limits).
• Build failures in edge code (fix the build first).
• 'Edge Runtime does not support' API errors (API surface problem).

Steps

Step 1: Identify what is bundled into the edge entry

Edge entries bundle everything they import. Trace imports from middleware.ts or the edge route.

Expected result: one or two heavy imports (SDKs, crypto libs, date libraries) dominate. Edge code must be lean.

Step 2: Trim the imports

Use scoped imports, lighter alternatives, or move the heavy work out of the edge entry into a serverless route the edge code calls.

Expected result: the edge bundle shrinks. Measure with the build output; Vercel reports the edge function size at build time.

Step 3: Keep edge code to edge jobs

Middleware should do routing, auth checks, redirects, and header manipulation. Business logic, DB access, and heavy computation belong in serverless functions or external services.

Expected result: the edge entry is thin glue. Size stays stable as the app grows.

Step 4: Check for accidental Node imports

Importing a Node-only package into edge code either fails or pulls in polyfills that balloon the bundle.

Expected result: edge imports are web-standard or edge-compatible only.

Step 5: Redeploy and watch the size

Expected result: the deploy passes size validation. Add the build-time size report to CI awareness so the next heavy import is caught before deploy.

Why it happens

Edge functions run on V8 isolates at the edge with tight size budgets for fast cold starts. Developers treat middleware like a Node server file and import freely. The bundler includes all of it, and the 1 MB cap is hit by a single kitchen-sink SDK.

Edge cases

• The limit applies per edge function, not per project. Splitting one fat middleware into route-scoped edge functions can help.
• Dynamic imports do not dodge the limit; the bundler still includes the chunks in the edge output.
• Middleware runs on EVERY request. Even under the limit, heavy middleware slows every page load.
• If the logic genuinely needs the weight, move it to a Node serverless function and call it from the edge.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstJjYNRbVTjFrSO4za41BOg

Resolved from the public thread: https://vectle.com/posts/pstJjYNRbVTjFrSO4za41BOg

Thread query: vercel edge function failed: 'Edge Function size exceeds 1 MB'

TL;DR: Vercel Edge Functions (including middleware) must stay under 1 MB. Heavy imports bundled into the edge entry push it over. Audit the edge bundle, trim or externalize heavy dependencies, and keep edge code to routing, auth checks, and rewrites.