How to fix diff tool 'vimdiff' is not available in Git

First, see what Git is trying to use:

git config --get diff.tool

If this returns nothing, Git will try to use a default tool. To see all available built-in tools, run:

git difftool --tool-help

This shows which tools Git recognizes and which are currently available on your system.

Check if your diff tool is actually installed and accessible:

# For vimdiff (vim)
vim --version

# For meld
meld --version

# For Beyond Compare (Windows)
bcomp /?

# Generic check if tool is in PATH
which vimdiff  # Linux/macOS
where meld     # Windows

If the command is not found, you need to install the tool first.

Install the diff tool if it's missing:

Ubuntu/Debian:

sudo apt update
sudo apt install vim        # for vimdiff
sudo apt install meld       # for meld

macOS:

brew install vim
brew install meld

Windows:
- Download and install [Meld](https://meldmerge.org/)
- Or [Beyond Compare](https://www.scootersoftware.com/)
- Or use vim from [Git for Windows](https://gitforwindows.org/) (includes vimdiff)

Red Hat/CentOS/Fedora:

sudo yum install vim-enhanced
sudo yum install meld

Set the diff tool in your Git configuration:

For vimdiff:

git config --global diff.tool vimdiff
git config --global difftool.prompt false

For meld:

git config --global diff.tool meld
git config --global difftool.prompt false

For Beyond Compare 3:

git config --global diff.tool bc3
git config --global difftool.prompt false

The difftool.prompt false setting prevents Git from asking for confirmation before launching the tool each time.

If the tool is installed but not in your system PATH, configure the full path:

Windows (Beyond Compare 4):

git config --global difftool.bc3.path 'C:/Program Files/Beyond Compare 4/bcomp.exe'

Windows (Meld):

git config --global difftool.meld.path 'C:/Program Files/Meld/Meld.exe'

macOS/Linux (custom location):

git config --global difftool.meld.path '/usr/local/bin/meld'

Note: Use forward slashes (/) even on Windows, or escape backslashes properly.

Verify git difftool now works:

# Make a change to a tracked file
echo 'test change' >> README.md

# Try launching difftool
git difftool

Your configured diff tool should open and display the changes. If you want to see all changes in directory diff mode:

git difftool -d

This copies modified files to a temp location and shows a directory comparison, which is more efficient for reviewing many files.