What is a Stack?
A stack defines the underlying operating system, runtime libraries, and system dependencies your application runs on. Gigalixir stacks are based on Heroku’s stacks, which are based on Ubuntu LTS releases.
| Stack | Base Image | Ubuntu Version |
|---|---|---|
| gigalixir-24 | heroku-24 | Ubuntu 24 |
| gigalixir-22 | heroku-22 | Ubuntu 22 |
| gigalixir-20 | heroku-20 | Ubuntu 20 |
| gigalixir-18 | heroku-18 | Ubuntu 18 |
| gigalixir-16 | heroku-16 | Ubuntu 16 |
| gigalixir-14 | heroku-14 | Ubuntu 14 |
The default stack for new apps is gigalixir-24.
For information about what packages are available in each stack, see the Packages & Dependencies documentation.
Stack Lifecycle
Over time, stacks stop receiving upstream security updates and must be retired. Each stack follows a predictable lifecycle with clear milestones.
| Phase | What It Means |
|---|---|
| Available | Fully supported. New apps can be created and existing apps can deploy and scale. |
| Sunsetting | Free tier apps are shut down. No new free tier apps can be created on this stack. Standard tier apps continue running and deploying. |
| Extended Support | Standard tier only. No new apps can be created. Billed at 2× standard pricing. |
| Retired | All apps are shut down. Deploys and scaling are disabled. |
Support Timeline
Each stack receives the following support window:
- 4 years of full support
- 6 months of additional full support for Standard tier during Sunsetting
- 18 months of Extended Support for Standard tier at increased cost
Current Stack Timeline
| Stack | Available | Sunsetting | Extended Support | Retired |
|---|---|---|---|---|
| gigalixir-26 | June 2026 | June 2030 | December 2030 | June 2032 |
| gigalixir-24 | May 2024 | June 2028 | December 2028 | June 2030 |
| gigalixir-22 | May 2022 | June 2026 | March 2027 | June 2028 |
| gigalixir-20 | 2020 | June 2026 | December 2026 | June 2028 |
| gigalixir-18 | 2018 | June 2026 | September 2026 | June 2027 |
| gigalixir-16 | 2016 | June 2026 | June 2026 | December 2026 |
| gigalixir-14 | 2014 | June 2026 | June 2026 | December 2026 |
Apps on retired stacks will be shut down and deploys disabled. We recommend upgrading before your current stack enters Extended Support or retirement.
How to Check Your Stack
You can view your app’s current stack using the Gigalixir CLI:
gigalixir apps:info
Or:
gigalixir ps
How to Select a Stack
When creating a new app, you can specify the stack:
gigalixir create --stack gigalixir-24
How to Upgrade Your Stack
To change the stack for an existing app:
gigalixir stack:set --stack gigalixir-24
After changing the stack, you must rebuild and redeploy your application.
We strongly recommend testing your application on the new stack in a staging environment before upgrading production.
Questions
If you have any questions or need help planning your stack upgrade, please contact Gigalixir Support.