How to replace Diffuse?

It is possible to install from manually downloaded packages from 18.04 LTS:

cd ~/Downloads
wget http://archive.ubuntu.com/ubuntu/pool/universe/p/pygtk/python-gtk2_2.24.0-5.1ubuntu2_amd64.deb
wget http://archive.ubuntu.com/ubuntu/pool/universe/d/diffuse/diffuse_0.4.8-3_all.deb
sudo apt-get install ./diffuse_0.4.8-3_all.deb ./python-gtk2_2.24.0-5.1ubuntu2_amd64.deb

Other good alternatives are Meld (meld package) or KDiff3 (kdiff3 package).

The package was dropped from Debian back in 2019, thence from Ubuntu also.

• Looks like it was abandoned upstream. Their mailing list has no responses from the developers for several years.

As of summer 2020, the updated fork of diffuse at https://github.com/MightyCreak/diffuse is the best way to go. It is very usable directly from source on Ubuntu 20.04. The main prerequisites are python3 and python3-gi, both of which are new enough on Ubuntu 20.04. Install python3 and python3-gi with

sudo apt install python3-gi

On non-desktop machines, you may need to install also the following packages that are otherwise typically installed already:

sudo apt install gobject-introspection gir1.2-gtk-3.0 gnome-icon-theme python3-gi-cairo

Then clone the diffuse fork from github to a folder of your liking. To run diffuse, it's sufficient to call the python script src/usr/bin/diffuse. It may be even more convenient to add the bin-folder to your PATH:

export PATH="${HOME}/your/path/to/diffuse/src/usr/bin:${PATH}"

The path setting can also be placed in your shells startup scripts (i.e. .bashrc or similar) to have diffuse always available.