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Setting your Bun Version

Current default Bun version

1.4.4

Services created before 2026-10-22 have a different default version. See below.

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

  • Set your service's Bun version using one of the methods below.
  • Include a bun.lock or bun.lockb file in your service's root directory.

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:

    Setting the BUN_VERSION environment variable

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

Supported version values

ValueDescription

A semantic version number (such as 1.4.4)

Uses the exact Bun version specified for every deploy. Recommended for most services.

latest

Uses the most recent stable release of Bun for every deploy.

canary

Uses the most recent canary build of Bun for every deploy.

Using latest or canary might introduce breaking changes in your service.

  • Because these versions change over time, a future release might be incompatible with your service's code or configuration.
  • Never use canary for a production service. Canary builds are untested pre-releases.
    • Instead, use canary in non-production services to preview upcoming Bun changes.

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 DateDefault Bun Version
2026-10-22 and later1.4.4
2026-10-12 to 2026-10-221.4.3
2026-09-09 to 2026-10-121.4.2
2026-07-16 to 2026-09-091.3.14
2025-12-08 to 2026-07-161.3.4
2025-08-18 to 2025-12-081.2.20
Before 2025-08-181.1.0

Setting your Bun Version
  • Supported version values
  • History of default Bun versions
Partially Degraded Service
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