errors/generatebuildid-not-a-string.mdx

---
title: '`generateBuildId` did not return a string'
---

## Why This Error Occurred

The most common cause for this issue is a custom `next.config.js` with the `generateBuildId` method defined, but it does not return a string.

## Possible Ways to Fix It

Always return a string from generateBuildId.
docs: Migrate error messages to MDX and App Router. (#52038) This PR is part of a larger effort to migrate error messages to MDX and use App Router: https://github.com/vercel/front/pull/23459 2023-07-05 14:11:16 +01:00			`---`
			title: '`generateBuildId` did not return a string'
			`---`
Trim buildId returned from generateBuildId (#5634) * Trim buildId returned from generateBuildId * Pass dir to function 2018-11-12 15:57:48 +01:00
docs: Migrate error messages to MDX and App Router. (#52038) This PR is part of a larger effort to migrate error messages to MDX and use App Router: https://github.com/vercel/front/pull/23459 2023-07-05 14:11:16 +01:00			`## Why This Error Occurred`
Trim buildId returned from generateBuildId (#5634) * Trim buildId returned from generateBuildId * Pass dir to function 2018-11-12 15:57:48 +01:00
			The most common cause for this issue is a custom `next.config.js` with the `generateBuildId` method defined, but it does not return a string.

docs: Migrate error messages to MDX and App Router. (#52038) This PR is part of a larger effort to migrate error messages to MDX and use App Router: https://github.com/vercel/front/pull/23459 2023-07-05 14:11:16 +01:00			`## Possible Ways to Fix It`
Trim buildId returned from generateBuildId (#5634) * Trim buildId returned from generateBuildId * Pass dir to function 2018-11-12 15:57:48 +01:00
			`Always return a string from generateBuildId.`