cargo-avail

Check whether crate names are truly available on crates.io.

Unlike simple "does this crate exist?" checkers, cargo-avail uses the actual crates.io validation logic to catch names that would be rejected at publish time:

• Syntactic validation (character rules, length limits, leading digits)
• Reserved names (Rust internals like std, core, alloc; Windows device names like nul, con, aux, com0-com9, lpt0-lpt9)
• Canonical collision detection (hyphens and underscores are equivalent: foo-bar and foo_bar are the same crate)
• crates.io API lookup with canonical matching

Install

cargo install cargo-avail

Usage

# Check one or more names
cargo avail my-crate another-name

# Pipe names from stdin
printf "my-crate\nanother-name\n" | cargo avail

# Only show available names
cargo avail -a name1 name2 name3

# Quiet mode: exit code only
cargo avail -q my-crate

# JSON output for scripting
cargo avail --json my-crate another-name | jq '.status'

# Print version
cargo avail --version

Output

Tab-separated: name\tstatus

my-crate        available
serde           taken
std             reserved
foo+bar         invalid: invalid character `+` in crate name: `foo+bar`, characters must be ASCII alphanumeric, `-`, or `_`

With --json, one JSON object per line (NDJSON):

{"name":"my-crate","status":"available"}
{"name":"serde","status":"taken"}
{"name":"std","status":"reserved"}
{"name":"foo+bar","status":"invalid","error":"invalid character `+` in crate name: `foo+bar`, characters must be ASCII alphanumeric, `-`, or `_`"}

Exit Codes

Code	Meaning
0	All names are available
1	One or more names are unavailable (taken, reserved, or invalid)
2	Usage error (no names provided, stdin read failure)
3	Partial failure: some names could not be checked (network error)

Library Usage

cargo-avail also exposes a library crate for programmatic use:

use cargo_avail::check::{Client, check_name, Availability};

let client = Client::new();
match check_name(&client, "my-cool-crate") {
    Ok(Availability::Available) => println!("go grab it!"),
    Ok(status) => println!("{status}"),
    Err(e) => eprintln!("error: {e}"),
}

Limitations

• Cannot detect recently deleted crates (requires database access).
• A name passing all checks could still fail at publish time due to server-side race conditions or policy changes.

License

GPLv3. See LICENSE.