SwiftLint

SwiftLint is a free, open-source linter that checks Swift code against community style conventions. It suits Swift developers who want configurable checks in their editor, build, or CI workflow. Its broad rule set and integrations make it a practical choice, provided your code compiles and SwiftLint uses the project’s toolchain.

Overview

SwiftLint combines a command-line interface with configurable rules for Swift projects. Its rules are predominantly based on SwiftSyntax; some use Clang and SourceKit to access type information. The command line also supports analysis, baselines, rule listings, and multiple reporters.

Over 200 built-in rules give teams a substantial starting point. Opt-in rules are disabled by default, so projects can choose stricter checks deliberately rather than inherit every rule. A .swiftlint.yml file controls enabled rules, paths to include or exclude, and rule settings.

Key features

Rules and corrections

Teams can define custom Swift rules, but those require building with Bazel. Regex-based custom rules are a more accessible option because official builds can run them. SwiftLint can also fix certain violations with --fix or --autocorrect. That saves manual edits for correctable issues, but corrections overwrite affected files on disk; review changes and keep a safe version of the source before applying them.

Project integrations

SwiftLint integrates with Xcode through a build tool plugin or a Run Script Build Phase, and with Swift Package Manager as a command or build tool plugin. Other documented connections include pre-commit, Fastlane, Docker, Visual Studio Code through the vscode-swiftlint extension, and MegaLinter. This range makes it feasible to run checks during local editing, builds, and CI rather than relying on a separate manual pass.

The build tool plugin does not directly support configurations outside the package or project directory, which can complicate repositories that centralize configuration elsewhere. The documentation also warns that disabling Xcode plugin and macro validation bypasses validation dialogs and implicitly trusts those components—an important security trade-off for unattended use.

Pricing

SwiftLint is free and open source, with no paid tier or trial to weigh against its core functionality. It is maintained by volunteers in their free time, and its maintainers say it is not a commercial product. Users who need help sustaining it can contribute, report issues, and support the community; volunteer time is limited, so this is not a substitute for a guaranteed commercial support arrangement.

Platforms

SwiftLint supports Linux, macOS, and Windows. The 0.65.1 release lists a universal macOS binary, Windows installers and AMD64 and ARM64 binaries, and AMD64 Linux binaries. Installation options include Homebrew, CocoaPods, Mint, Bazel, Swift Package Manager, prebuilt packages, and source builds.

Toolchain alignment matters: SwiftLint should run with the same Swift toolchain used to compile the project. Its development tests require Swift 6.1 or higher, while Swift Package Manager plugins work down to Swift 5.9. Check the toolchain requirements for the integration you plan to use rather than treating platform support alone as sufficient.

Who it's for

SwiftLint is a strong fit for Swift teams that want to enforce shared conventions across editors, builds, and CI, and that can configure rules to match their codebase. It is less suitable as a checker for code that is still syntactically broken: it is designed for valid, compilable source, and non-compiling code can produce unexpected results, especially with autocorrection. Analyzer rules are considerably slower than lint rules, so projects should account for that when deciding how broadly to run analysis.

Pros and cons

• Pros: More than 200 built-in rules and configurable opt-in checks let teams tune enforcement rather than accept a fixed style policy.
• Pros: Xcode and Swift Package Manager support, plus editor and CI integrations, fit SwiftLint into several stages of a project workflow.
• Pros: Free, MIT-licensed distribution and multiple installation routes make it accessible across supported platforms.
• Cons: It expects compilable Swift source, limiting its reliability while code is in an invalid state.
• Cons: Autocorrection overwrites files, so careless use can replace source changes.
• Cons: Matching the compiler’s toolchain and the plugin’s configuration-path restriction require setup attention; analyzer rules also run considerably slower than lint rules.
• Cons: Volunteer maintenance means support capacity is limited, which may not suit teams that require commercial support.

Alternatives

For Swift projects, SwiftLint is the focused option among these alternatives. Choose another tool when its language or target better matches your work:

• Biome is a free toolchain for web projects; choose it for web work rather than Swift linting.
• Cppcheck offers free core static analysis and a Project plan with custom pricing; consider it when C/C++ analysis is the need.
• Hadolint is a free, open-source Dockerfile linter; choose it for Dockerfiles.
• JSHint is a free JavaScript linter; choose it for JavaScript rather than Swift.
• PMD is a free, downloadable static code analyzer; consider it for code analysis outside SwiftLint’s specific Swift focus.
• Ruff is an open-source developer tool in the Python ecosystem; choose it for Python work.
• ShellCheck is free static analysis for shell scripts, available on the web, terminal, or in editors; choose it for shell code.
• actionlint is a free, MIT-licensed command-line static checker with a browser playground; consider it for the checks it provides.

Browse more options in Linters.

Verdict

SwiftLint is an easy recommendation for Swift developers who want a free, adaptable style checker integrated into their project workflow. Its rule depth and broad integration options are the main reasons to choose it. Look elsewhere if you need analysis of non-compiling code, guaranteed commercial support, or a tool for a language other than Swift.