Markdown Linter
Lint markdown style and structure issues
Input Markdown
Lint Report
What is a Markdown Linter?
A markdown linter is a code quality tool that analyzes markdown files and reports style violations, formatting inconsistencies, and structural issues that make documentation harder to read and maintain. Similar to how markdownlint works on desktop, this browser-based linter runs locally and identifies issues without uploading your content anywhere. Linting ensures all markdown files follow consistent rules, making them more professional and easier to work with across teams.
Most markdown linters check for problems like incorrectly nested heading levels (jumping from H1 directly to H3), excessive line lengths that wrap awkwardly, inconsistent list markers (mixing bullet styles), and missing blank lines around headings. The markdownlint project defines a comprehensive ruleset that has become the industry standard, with over 40 different rules covering everything from trailing spaces to code fence consistency.
By catching these issues early, a markdown linter saves time during documentation reviews and prevents reader confusion. The browser-based approach here means instant feedback on your markdown without any external dependencies, making it perfect for writing documentation, READMEs, blog posts, and technical guides in real time.
How to Use the Markdown Linter
Follow these steps to lint your Markdown for style and structure. Each step uses the actual buttons and panels on this page.
Paste, Upload, or Load Sample
Paste Markdown into the left Input Markdown panel, or click Upload to load a .md file. Click Sample to see example subscriber API docs with intentional style issues. Checks heading hierarchy, line length, list consistency, trailing whitespace.
View Lint Report
The right Lint Report panel lists issues with line numbers and descriptions. Fix heading jumps, long lines, mixed list markers, and spacing problems.
Copy or Download Report
Click Copy or Download to use the report. Use Clear to start fresh. All processing runs in your browser.
When You'd Actually Use This
Documentation Review Workflows
Before submitting pull requests for documentation updates, run the linter to catch style violations. This ensures consistency across your project's docs and reduces back-and-forth with reviewers over formatting issues. Teams maintaining large documentation sites like GitHub Docs use similar tools in their CI/CD pipelines.
Technical Writing Standards
Enforce consistent heading structure and formatting across blog posts, tutorials, and guides. Maintains professional appearance and ensures readers can navigate using headings predictably. Especially important for markdown-heavy platforms like dev.to or Medium.
Open Source Project Maintenance
Check contributor-submitted documentation for compliance with your project's style guide before merging. Running linter checks locally helps contributors self-correct before creating issues, reducing maintenance burden. Many projects add linting to GitHub Actions workflows.
Quick Content Quality Checks
Use it for a final pass on README files, API documentation, and release notes before publication. Catches easy-to-miss issues like extra spaces and invalid heading sequences that look unprofessional to readers. Particularly useful when content goes through multiple authors.
Common Questions (FAQ)
What's the difference between a linter and a validator?
A validator checks whether markdown is syntactically correct and renders properly. A linter goes further and enforces style consistency and best practices. Think of validation like spell-checking and linting like grammar-checking. The markdownlint documentation clarifies this distinction—a file can be valid markdown but fail linting checks.
Can I customize which rules the linter checks?
This browser-based linter uses a built-in default ruleset focused on the most common issues. If you need full customization, the desktop markdownlint package allows you to enable/disable specific rules via configuration files.
Does the linter send my markdown to any servers?
No—all linting happens entirely in your browser using JavaScript. Your markdown content never leaves your computer. This makes it safe for proprietary documentation, private projects, and sensitive information.
What markdown flavor does this linter support?
This linter follows CommonMark specification as the baseline, which is the most portable and widely supported markdown standard. GitHub Flavored Markdown extends CommonMark with tables and strikethrough.
How do I fix issues the linter finds?
Each issue in the report includes the line number and a description. Common fixes: reorder headings logically, remove trailing spaces, add blank lines around headings, keep lines under 80 characters, and use consistent list markers. The Markdown Guide has detailed syntax examples.
Can I use this for production documentation checks?
For one-off checks, yes. For automated enforcement in CI/CD pipelines, integrate the command-line markdownlint-cli into your build process on platforms like GitHub Actions, GitLab CI, or Jenkins.