Build image

Workers Builds uses a build image with support for a variety of languages and tools such as Node.js, Python, PHP, Ruby, and Go.

Supported Tooling

Workers Builds supports a variety of runtimes, languages, and tools. Builds will use the default versions listed below unless a custom version is detected or specified. You can override the default versions using environment variables or version files. All versions are available for override.

Default version updates

The default versions will be updated regularly to the latest minor version. No major version updates will be made without notice. If you need a specific minor version, please specify it by overriding the default version.

Runtime

Tool	Default version	Environment variable	File
Go	1.24.3	GO_VERSION
Node.js	22.16.0	NODE_VERSION	.nvmrc, .node-version
Python	3.13.3	PYTHON_VERSION	.python-version, runtime.txt
Ruby	3.4.4	RUBY_VERSION	.ruby-version

Tools and languages

Tool	Default version	Environment variable
Bun	1.2.15	BUN_VERSION
Hugo	extended_0.147.7	HUGO_VERSION
npm	10.9.2
yarn	4.9.1	YARN_VERSION
pnpm	10.11.1	PNPM_VERSION
pip	25.1.1
gem	3.6.9
poetry	2.1.3
pipx	1.7.1
bundler	2.6.9

Advanced Settings

Overriding Default Versions

If you need to override a specific version of a language or tool within the image, you can specify it as a build environment variable, or set the relevant file in your source code as shown above.

To set the version using a build environment variables, you can:

1. Find the environment variable name for the language or tool and desired version (e.g. NODE_VERSION = 22)
2. Add and save the environment variable on the dashboard by going to Settings > Build > Build Variables and Secrets in your Workers project

Or, to set the version by adding a file to your project, you can:

1. Find the filename for the language or tool (e.g. .nvmrc)
2. Add the specified file name to the root directory and set the desired version number as the file's content. For example, if the version number is 22, the file should contain '22'.

Skip dependency install

You can add the following build variable to disable automatic dependency installation and run a custom install command instead.

Build variable	Value
SKIP_DEPENDENCY_INSTALL	1 or true

Pre-installed Packages

In the following table, review the pre-installed packages in the build image. The packages are installed with apt, a package manager for Linux distributions.

curl	libbz2-dev	libreadline-dev
git	libc++1	libssl-dev
git-lfs	libdb-dev	libvips-dev
unzip	libgdbm-dev	libyaml-dev
autoconf	libgdbm6	tzdata
build-essential	libgbm1	wget
bzip2	libgmp-dev	zlib1g-dev
gnupg	liblzma-dev	zstd
libffi-dev	libncurses5-dev

Build Environment

Workers Builds are run in the following environment:

Build Environment	Ubuntu 24.04
Architecture	x86_64

Build Image Policy

Preinstalled Software Updates

Preinstalled software (languages and tools) will be updated before reaching end-of-life (EOL). These updates apply only if you have not overridden the default version.

• Minor version updates: May be updated to the latest available minor version without notice. For tools that do not follow semantic versioning (e.g., Bun or Hugo), updates that may contain breaking changes will receive 3 months’ notice.
• Major version updates: Updated to the next stable long-term support (LTS) version with 3 months’ notice.

How you'll be notified (for changes requiring notice):

• Cloudflare Changelog ↗
• Dashboard notifications for projects that will receive the update
• Email notifications to project owners

To maintain a specific version and avoid automatic updates, override the default version.

Best Practices

To avoid unexpected build failures:

• Monitor announcements via the Cloudflare Changelog ↗, dashboard notifications, and email
• Pin specific versions of critical preinstalled software by overriding default versions