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cargo-tarpaulin

cargo-tarpaulin is an Apache-2.0 code coverage tool for Rust projects, with ptrace and LLVM engines and HTML, LCOV, Cobertura XML and JSON reports plus Coveralls and Codecov support.

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Introduction

Tarpaulin is a code coverage reporting tool for the Cargo build system. It runs your tests and records which lines executed, then produces reports for humans and CI services. It has long been a popular choice in Rust CI pipelines because it is installed as a single cargo subcommand.

Its README explains that on Linux the default tracing backend is still ptrace, which only works on x86_64, and that you can switch to LLVM coverage instrumentation with --engine llvm; on macOS and Windows, LLVM is the default. Tarpaulin can also run in Docker for developers not on Linux. Output formats include HTML, LCOV, Cobertura XML and JSON, and it can upload directly to Coveralls, with LCOV or XML reports used for Codecov. Options cover workspaces, features, ignoring tests or panics, excluding files and failing under a coverage threshold (--fail-under). Version 0.37.6 was released on 5 November 2026.

The source code is at xd009642/tarpaulin on GitHub under the Apache-2.0 licence, with about 3,000 stars; the most recent commit was on 10 November 2026.

Features

  1. Single subcommand: cargo tarpaulin in any project.
  2. Two engines: ptrace on Linux x86_64 or LLVM instrumentation.
  3. Many formats: HTML, LCOV, Cobertura XML and JSON.
  4. Thresholds: --fail-under for CI gates.

Pros

  1. Free to use: Open source under the Apache-2.0 licence, so the core tool costs nothing to use.
  2. Actively maintained: The repository had commits as recent as 10 November 2026.
  3. Community: About 3,000 GitHub stars.

Cons

  1. Platform caveats: The ptrace engine is Linux x86_64 only.
  2. Accuracy differences: Line coverage can differ from LLVM region coverage tools.
cargo install cargo-tarpaulin
cargo tarpaulin --out Html --out Lcov
cargo tarpaulin --engine llvm --fail-under 80

Resources:

Pricing

cargo-tarpaulin is free and open source under the Apache-2.0 licence.

  1. Rust teams wanting simple coverage in CI.
  2. Projects reporting to Coveralls or Codecov.

Conclusion

cargo-tarpaulin is a long-standing, easy coverage tool for Rust; cargo-llvm-cov is an alternative when precise LLVM region coverage matters.

Alternatives

Other tools on CheckOps that cover similar ground. Open a page, or compare one with cargo-tarpaulin side by side.