linter

A linter is a static analysis tool used in software development to examine source code for patterns that may indicate errors, bugs, stylistic inconsistencies, or potential security risks. Linters operate without executing the program, relying on rules to flag issues and guide developers toward higher code quality.

The term originates from the Unix tool lint, developed to detect quality issues in C code. Over time, linters have expanded to many languages and domains, delivering early feedback during editing, code review, and continuous integration.

Most linters analyze code by parsing it into a representation such as tokens or an abstract syntax tree, then applying a set of rules. Issues are reported with location, rule name, and a brief message. Some linters can automatically fix certain problems or reformat code.

Common examples include ESLint for JavaScript, PyLint for Python, RuboCop for Ruby, golangci-lint for Go, and ShellCheck for shell scripts. Linters may focus on style guidelines, potential correctness, reliability, complexity, or security vulnerabilities. They can be language-specific or multi-language and may support customizable rule sets and plugins.

Linters are frequently integrated into editors and IDEs, as well as into continuous integration pipelines, enabling automated checking on save or upon commits. They rely on configuration files to enable, disable, or tailor rules to a project’s standards; overly strict configurations can increase noise.

While powerful, linters are not substitutes for testing or formal verification. They may produce false positives or negatives and require tuning. They complement formatters, which focus on code appearance, by catching broader issues through static analysis.