Workflow triggers and scheduled runs

Workflow triggers are the events that cause a workflow to run: activity on GitHub, a scheduled time, or an external event, and not all webhook events trigger workflows. Many events have multiple activity types, and the types keyword limits runs to specific ones. The schedule event uses five-field POSIX cron syntax; runs are in UTC by default, accept an IANA timezone string, occur at most once every 5 minutes, and always target the latest commit of the default branch. Schedules can be delayed under high load — including the start of every hour — and in public repositories scheduled workflows are disabled after 60 days without repository activity; non-standard shortcuts like @daily or @weekly are unsupported. Workflows do not run on pull_request activity while a merge conflict exists. For mergeable pull requests, GITHUB_REF points at the merge branch, so actions/checkout tests the merged result; check out github.event.pull_request.head.sha to test only head commits. Pull requests created or updated with GITHUB_TOKEN require write-access approval for opened, synchronize, or reopened runs; other GITHUB_TOKEN-triggered events, except workflow_dispatch and repository_dispatch, create no runs at all. Scope: GitHub Actions. Reviewed October 4, 2026.