Actions authors can now specify that their action can run in Node.js 16 by specifying runs.using as node16 in the action's action.yml. This is in addition to the existing Node.js 12 support; actions can continue to specify runs.using: node12 to use the Node.js 12 runtime.

Runners supporting Node.js 16 actions are available on all GitHub-hosted runners and in GitHub Enterprise Server 3.4 and newer. GitHub Enterprise Server 3.3 and newer can manually install a newer runner to add support for Node.js 16 based actions.

As a result, actions authors who move from targeting Node.js 12 to Node.js 16 should release with a new major version number to communicate that there is a possible breaking change for GitHub Enterprise Server 3.3 and earlier.