cargo run vs cargo build

cargo build compiles your project into a runnable binary, but it doesn't run that binary for you — it just leaves it sitting in the target/debug folder, waiting. cargo run does both steps in one: it compiles the project (recompiling only if something changed since last time) and then immediately runs the resulting binary.

cargo build
./target/debug/my_project

# vs. doing both in one step:
cargo run

There's also cargo check, which is faster than either: it asks the compiler to verify your code is correct without actually producing a runnable binary at all. It's handy while you're still writing code and just want quick feedback on whether it compiles.

Running ____ compiles a Rust project and then immediately runs the resulting binary, all in one step.

By default, both cargo build and cargo run produce a debug build: fast to compile, but not very optimized, and placed in target/debug. Adding the --release flag, as in cargo build --release, produces a much more optimized binary in target/release — it takes noticeably longer to compile, but the resulting program runs significantly faster, which is what you'd ship to real users.

cargo build --release
./target/release/my_project

Running cargo build without any flags produces an optimized binary in target/release.