This article lists the supported variables you can use in GitHub Actions workflows, including environment variables, configuration variables, and default variables provided by GitHub. Use this reference to look up variable names, naming conventions, limits, and supported contexts when configuring your workflows.

For more information about variables, seeVariables.

Default environment variables

The default environment variables that GitHub sets are available to every step in a workflow.

Because default environment variables are set by GitHub and not defined in a workflow, they are not accessible through theenv context. However, most of the default variables have a corresponding, and similarly named, context property. For example, the value of theGITHUB_REF variable can be read during workflow processing using the${{ github.ref }} context property.

You can't overwrite the value of the default environment variables namedGITHUB_* andRUNNER_*. Currently you can overwrite the value of theCI variable. However, it's not guaranteed that this will always be possible. For more information about setting environment variables, seeStore information in variables andWorkflow commands for GitHub Actions.

We strongly recommend that actions use variables to access the filesystem rather than using hardcoded file paths. GitHub sets variables for actions to use in all runner environments.

Naming conventions for configuration variables

The following rules apply to configuration variable names:

• Can only contain alphanumeric characters ([a-z],[A-Z],[0-9]) or underscores (_). Spaces are not allowed.
• Must not start with theGITHUB_ prefix.
• Must not start with a number.
• Are case insensitive when referenced. GitHub stores secret names as uppercase regardless of how they are entered.
• Must be unique to the repository, organization, or enterprise where they are created.

Naming conventions for environment variables

When you set an environment variable, you cannot use any of the default environment variable names. For a complete list of default environment variables, seeVariables reference below. If you attempt to override the value of one of these default variables, the assignment is ignored.

Configuration variable precedence

If a variable with the same name exists at multiple levels, the variable at the lowest level takes precedence. For example, if an organization-level variable has the same name as a repository-level variable, then the repository-level variable takes precedence. Similarly, if an organization, repository, and environment all have a variable with the same name, the environment-level variable takes precedence.

For reusable workflows, the variables from the caller workflow's repository are used. Variables from the repository that contains the called workflow are not made available to the caller workflow.

Limits for configuration variables

Individual variables are limited to 48 KB in size.

You can store up to 1,000 organization variables, 500 variables per repository, and 100 variables per environment. The total combined size limit for organization and repository variables is 256 KB per workflow run.

A workflow created in a repository can access the following number of variables:

• Up to 500 repository variables, if the total size of repository variables is less than 256 KB. If the total size of repository variables exceeds 256 KB, only the repository variables that fall below the limit will be available (as sorted alphabetically by variable name).
• Up to 1,000 organization variables, if the total combined size of repository and organization variables is less than 256 KB. If the total combined size of organization and repository variables exceeds 256 KB, only the organization variables that fall below that limit will be available (after accounting for repository variables and as sorted alphabetically by variable name).
• Up to 100 environment-level variables.

Supported contexts

You will commonly use either theenv orgithub context to access variable values in parts of the workflow that are processed before jobs are sent to runners.