whatsdiff requires PHP 8.3 or higher and Composer.
Global installation
Install it globally so the whatsdiff command works in every project:
composer global require whatsdiff/whatsdiff
Check that it worked:
whatsdiff --version
The same install puts whatsdiff-mcp on your path. See MCP setup to connect it to your AI assistant.
Running it with cpx
cpx is Composer's answer to npx: it runs a command from any package without installing it, keeping the package isolated from both your project and your global Composer setup.
composer global require cpx/cpx
Then run whatsdiff without installing it at all:
cpx whatsdiff/whatsdiff analyse
Pin a version with standard Composer constraint syntax:
cpx whatsdiff/whatsdiff:^2.0 analyse
The first run downloads the package, and later runs reuse it. This suits a CI job or a one-off check on a machine you would rather not install anything on. For daily use, the global install is less typing.
Updating
composer global update whatsdiff/whatsdiff
Next, read the CLI overview for the available commands.