Heroku-26 stack is now generally available

Change effective on 20 May 2026

Heroku-26, our stack based on Ubuntu 26.04 Long Term Support, is now generally available. It will be supported until the end of April 2031.

The Heroku-24 stack remains the default stack for newly created applications until further notice.

The method for testing and upgrading to the new stack varies based on the generation of your app.

For Cedar-generation apps:

If your organization uses Review Apps or Heroku CI, we recommend testing Heroku-26 by defining your stack in app.json:

{
  "stack": "heroku-26"
}

Existing apps can be upgraded by running this command and pushing a new build:

$ heroku stack:set heroku-26

For Fir-generation apps:

For Fir apps, the name of an app’s stack is always set to cnb, and the base image is instead tied to the CNB builder, which can be controlled via your app’s project.toml file for both new and existing apps.

For instance, setting builder = "heroku/builder:26" in project.toml causes Heroku to use the Heroku-26 base image:

[_]
schema-version = "0.2"

[io.buildpacks]
builder = "heroku/builder:26"

For more information, see the Heroku-26 stack article.