Setting your Bun Version – Render Docs

Current default Bun version
1.4.2
Services created before 2026-09-09 have a different default version. See below.

To include Bun in your service's environment, you must do at least one of the following:

Otherwise, your service's environment will not include Bun.

Set your service's Bun version in any of the following ways (in descending order of precedence):

  1. Set the BUN_VERSION environment variable for your service in the Render Dashboard:

  2. Add a file named .bun-version to the root of your repo. This file contains a single line with the version to use:

.bun-version

1.4.2

You can specify either a semantic version number (such as 1.3.4) or use latest to always use the most recent version of Bun with every deploy.

History of default Bun versions

If you don't set a Bun version for your service, Render's default version depends on when you originally created the service:

Service Creation Date Default Bun Version
2026-09-09 and later 1.4.2
2026-07-16 to 2026-09-09 1.3.14
2025-12-08 to 2026-07-16 1.3.4
2025-08-18 to 2025-12-08 1.2.20
Before 2025-08-18 1.1.0