Scarb is the package manager and build toolchain for Starknet ecosystem. Those coming from Rust ecosystem will find Scarb very similar to Cargo.

Starknet Foundry uses Scarb to:

One of the core concepts of Scarb is its manifest file - Scarb.toml. It can be also used to provide configuration for Starknet Foundry Forge. Moreover, you can modify behaviour of scarb test to run snforge test as described here.

📝 Note Scarb.toml is specifically designed for configuring scarb packages and, by extension, is suitable for snforge configurations, which are package-specific. On the other hand, sncast can operate independently of scarb workspaces/packages and therefore utilizes a different configuration file, snfoundry.toml. This distinction ensures that configurations are appropriately aligned with their respective tools' operational contexts.

Last but not least, remember that in order to use Starknet Foundry, you must have Scarb installed and added to the PATH environment variable.