Heroku-26 Stack

Last updated May 19, 2026

This article describes the Heroku-26 stack, based on Ubuntu 26.04. What is a stack?

What’s new

This stack is now based on Ubuntu 26.04, compared to Ubuntu 24.04 used in the Heroku-24 stack.

See the upgrade notes for more detailed change information.

Available software

Every stack on Heroku supports different operating system packages and language runtime versions. This support is typically confined to software that was still actively developed by the respective maintainers at the time the stack was first released.

Language runtimes

For the most accurate information on supported language runtime versions, please check the individual language pages:

Buildpack Shorthand Runtime versions
.NET heroku/dotnet Runtime versions
Go heroku/go Runtime versions
Java heroku/java Runtime versions
Node.js heroku/nodejs Runtime versions
PHP heroku/php Runtime versions
Python heroku/python Runtime versions
Ruby heroku/ruby Runtime versions

Operating system packages

For a full list of operating system packages available on Heroku-26, please refer to article Ubuntu Packages on Heroku Stacks.

Support period

Heroku-26 is based on Ubuntu 26.04. It will be supported through April 2031. Learn more about Heroku’s stack update policy.

Using Heroku-26

Heroku-24 is currently the default stack for newly created Cedar apps. It is also the default builder / base image for Fir apps.

Using Heroku-26 on Cedar

You can specify a stack when creating a Cedar app:

$ heroku create --stack heroku-26

You may change the stack on an existing app; the next build performed will then use the new stack:

$ heroku stack:set heroku-26

If you are using app.json, you should also specify the stack there to ensure that your Review Apps and Heroku CI runs use the same stack:

{
  "stack": "heroku-26"
}

An existing app’s stack cannot be changed using app.json. The stack specified is only applied to newly created apps that are a Review App, a Heroku CI test run app, or an app created using a Heroku Button.

Using Heroku-26 on Fir

The stack property of a Fir app is always cnb, and the base image is tied to the CNB builder, optionally defined in an app’s project.toml:

[_]
schema-version = "0.2"

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

Upgrading to Heroku-26

Please refer to the stack upgrading guide to understand the procedures to follow when upgrading to a new stack.

We recommend that you monitor your application closely after migrating an app to the new stack to ensure it’s performing correctly.

Upgrade notes

There are currently no known breaking OS changes that require action when upgrading from Heroku-24 to Heroku-26. If you do find a compatibility issue, please let us know via a support ticket or by using the “Submit Feedback” button at the bottom of this page.

Heroku-26 Docker images

Heroku-26 is available as two Docker images:

  1. The run time image (heroku/heroku:26), which is recommended over the build image for most workloads.
  2. The build image (heroku/heroku:26-build), which is larger as it includes development headers and toolchains. It is only recommended for customers that need to compile source code or dependencies.

Use the following command in your Dockerfile to use Heroku-26 as your base image:

FROM heroku/heroku:26

We publish these images as multi-architecture images, supporting both the amd64 and arm64 CPU architectures. By default Docker will use the image architecture that matches the machine on which it is being run. To force the use of a different architecture, pass --platform linux/<architecture> to docker build or docker run commands, or use FROM --platform=linux/<architecture> IMAGE_NAME in your Dockerfile.

The default Linux user for these images is heroku, which does not have root permissions. If you need to modify locations outside of /home/heroku or /tmp you will need to switch back to the root user. To do this add USER root to your Dockerfile when building images, or pass --user root to any docker run commands.

To learn more about deploying Docker images, please refer to the Heroku Container Registry and Runtime documentation.