# Replacing dependencies with patch

The `[patch]` section of your `Cargo.toml` can be used when you want to override certain parts of your dependency graph.

> Cargo has a `[replace]` feature that is similar; while we don't intend to deprecate or remove `[replace]`, you should prefer `[patch]` in all circumstances.

So what’s it look like? Let’s say we have a Cargo.toml that looks like this:

    [dependencies]
    foo = "1.2.3"

In addition, our `foo` package depends on a `bar` crate, and we find a bug in `bar`. To test this out, we’d download the source code for `bar`, and then update our `Cargo.toml`:

    [dependencies]
    foo = "1.2.3"

    [patch.crates-io]
    bar = { path = '/path/to/bar' }

Now, when you `cargo build`, it will use the local version of `bar`, rather than the one from crates.io that `foo` depends on. You can then try out your changes, and fix that bug!

For more details, see the documentation for `patch`.