If a library that our program depends on is published on https://crates.io/, all we have to do to link it is add its linking code to the dependencies section. Let's say we want to use serde (a tool for turning Rust data into formats such as JSON and back) in our program. First, we find its linking code with: cargo search serde.

This will print out a list of matches that looks something like this:

     serde = "1.0.70"                          # A generic serialization/deserialization framework
     serde_json = "1.0.24"                 # A JSON serialization file format
     serde_derive_internals = "0.23.1"     # AST representation used by Serde derive macros. Unstable.
     serde_any = "0.5.0"                   # Dynamic serialization and deserialization with the format chosen at runtime
     serde_yaml = "0.7.5"                 # YAML support for Serde
     serde_bytes = "0.10.4"              # Optimized handling of `&[u8]` and `Vec<u8>` for Serde
     serde_traitobject = "0.1.0"       # Serializable trait objects.  This library enables the serialization of trait objects such…
     cargo-ssearch = "0.1.2"             # cargo-ssearch: cargo search on steroids
     serde_codegen_internals = "0.14.2"    # AST representation used by Serde codegen. Unstable.
     serde_millis = "0.1.1"                #     A serde wrapper that stores integer millisecond value for timestamps     and duration…
     ... and 458 crates more (use --limit N to see more)

The first one is the core serde library, and the linking code is the part of the line before the # symbol. All we have to do is copy and paste that into the dependencies section of Cargo.toml, and Rust will know that it should compile and link serde when it compiles our foo program. So, the dependencies section of Cargo.toml would look like this:

 [dependencies]
 serde = "1.0.70"