Enable unstable applications in stable NixOS

Use this guide if you want to keep your NixOS on the stable branch, but enable unstable application packages. It took me a while to figure out how to do this, so I wanted to share because it ended up being far easier than most of the vague explanations online made it seem.

I put a sample configuration.nix file at the very bottom to help it make more sense for new users. Remember to keep a backup of your config file, just in case!

If there are any errors please let me know. I am currently running NixOS 24.11.

Steps listed in this guide:

1. Add the unstable channel to NixOS as a secondary channel.
2. Edit the configuration.nix to enable unstable applications.
3. Add "unstable." in front of the application names in the config file (example: unstable.program). This enables the install of unstable versions during the build.
4. Rebuild.

Step 1:

• Open the console. (If you want to see which channels you currently have, type: sudo nix-channel --list)
• Add the unstable channel, type: sudo nix-channel --add channels.nixos.org/nixpkgs-unstable unstable
• To update the channels (bring in the possible apps), type: sudo nix-channel --update

More info here: nixos.wiki/wiki/Nix_channels

Step 2:

Edit your configuration.nix and add the following around your current config:

{ config, pkgs, lib, ... }:

let
    unstable = import <unstable> { config = { allowUnfree = true; }; };
  in {

        #insert normal configuration text here

      } #remember to close the bracket!

At this point it would be good to save your config and try a rebuild to make sure there are no errors. If you have errors, make sure your brackets are in the right places and/or not missing. This step will make for less troubleshooting later on if something happens to be in the wrong spot!

Step 3:

Add "unstable." to the start of each application you want to use the unstable version. (Example: unstable.brave)

Step 4:

Rebuild your config, type: sudo nixos-rebuild switch

Example configuration.nix file:

# Config file for NixOS
{ config, pkgs, lib, ... }:

#Enable unstable apps from Nix repository.
  let
    unstable = import <unstable> { config = { allowUnfree = true; }; };
  in {

  #Put your normal config entries here in between the tags. Below is what your applications list needs to look like.

  environment.systemPackages = with pkgs; [
    appimage-run
    blender
    unstable.brave #Just add unstable. before the application name to enable the unstable version.
    chirp
    discord
  ];

  }    # Don't forget to close bracket at the end of the config file!

That should be all. Hope it helps.