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GitHub Actions is moving `ubuntu-latest` to Ubuntu 26.04 — test before October 19

Ubuntu 26.04 runners are now generally available in GitHub Actions, and the floating `ubuntu-latest` label will migrate from 24.04 between October 19 and November 19, potentially breaking workflows that rely on changed or removed preinstalled tools.

Reviewed and published by Lars Jansen Updated 4 min read
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Key details

  1. Ubuntu 26.04 GitHub-hosted Actions runners are generally available on x64 and arm64.
  2. Explicit runner labels include `ubuntu-26.04` and `ubuntu-26.04-arm`.
  3. `ubuntu-latest` will migrate from Ubuntu 24.04 to Ubuntu 26.04.
  4. The migration window runs from October 19 through November 19, 2026.
  5. Ubuntu 26.04 changes or removes some tools and tool versions compared with the previous image.
  6. Teams that are not ready can pin jobs to `ubuntu-24.04`.

What builders should take away

  1. Add an Ubuntu 26.04 CI job now for workflows that currently rely on `ubuntu-latest`, especially release and deployment pipelines.
  2. Inventory commands that rely on runner-preinstalled software rather than project-managed dependencies.
  3. During the rollout window, include the runner image/OS in failure diagnostics because different jobs may encounter different default images.
  4. Pin `ubuntu-24.04` if a production-critical workflow cannot be made compatible before October 19, then track that pin as migration debt.
  5. Prefer explicitly installed or version-managed build dependencies where reproducibility matters rather than treating a hosted runner image as a fixed environment.

What changed

GitHub has moved its Ubuntu 26.04 hosted runner image out of public preview and into general availability for x64 and arm64. The explicit labels are `ubuntu-26.04` and `ubuntu-26.04-arm`. More importantly, GitHub will gradually move the floating `ubuntu-latest` label from Ubuntu 24.04 to Ubuntu 26.04 between October 19 and November 19, 2026. Jobs that continue using `ubuntu-latest` will therefore change base operating system during that rollout without a workflow-file change.

Why it matters

Many CI pipelines implicitly depend on the packages, compilers, runtimes and command-line tools preinstalled in GitHub's hosted images. Ubuntu 26.04 updates and removes some of those components. A workflow that looks pinned because its YAML has not changed can consequently start failing when `ubuntu-latest` moves. The month-long gradual rollout also means two otherwise identical runs may encounter different images during migration, making hidden environment assumptions harder to diagnose.

Ubuntu 26.04 is available for explicit testing now

Teams can opt into the new image immediately with `runs-on: ubuntu-26.04`, or use `ubuntu-26.04-arm` for arm64. That gives maintainers a pre-migration window to run existing workflows against the environment that will become the default.

`ubuntu-latest` changes between October 19 and November 19

GitHub says the floating label will migrate gradually from Ubuntu 24.04 to 26.04 across this period. Workflows that use the label do not need a repository change to move; the runner selection changes underneath them as GitHub rolls out the new default.

Preinstalled-tool assumptions are the main compatibility risk

GitHub explicitly warns that Ubuntu 26.04 contains updated and, in some cases, removed tools and tool versions compared with the previous image. Builds that call a preinstalled binary or assume a particular system library, compiler or runtime can therefore fail even when application dependencies are otherwise locked.

Pinning 24.04 buys migration time

Teams that cannot move by the rollout can replace the floating label with `ubuntu-24.04`. That avoids the automatic OS jump, but it also turns the decision into an explicit migration that will eventually need its own maintenance plan.

What to watch next

  • The start of the `ubuntu-latest` migration on October 19, 2026.
  • Compatibility reports involving tools removed or materially changed in the Ubuntu 26.04 runner image.
  • The completion of the gradual migration by November 19, 2026.
  • Future retirement timing for the Ubuntu 24.04 hosted image.

Still unclear

  • The gradual rollout means GitHub does not promise that every `ubuntu-latest` job switches on the same day.
  • Whether an individual workflow breaks depends on its reliance on system packages and preinstalled tool versions.

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