How to Lint Markdown Files Without Installing Anything

You need to check a markdown file for style consistency, but you don't want to install Vale CLI, configure npm packages, or set up linting tools locally. Maybe you're on a borrowed computer, working on a system without admin rights, or just need a quick check before committing documentation changes.

Browser-based markdown linting solves this perfectly. No installation, no configuration, no local dependencies—just open a browser, paste your content, and get instant feedback from professional style guides.

Why zero-install linting matters

Installation friction kills productivity. Every tool you need to install, configure, and maintain adds overhead to simple tasks. For markdown linting, this overhead often exceeds the actual work:

Quick checks shouldn't require setup: When you just need to verify a README before pushing to GitHub, spending 15 minutes installing and configuring Vale CLI is overkill.

Not every environment allows installations: Corporate laptops with restricted admin rights, shared workstations, temporary computers, or systems you don't control make local tool installation impossible.

Contributors won't install tools: Open-source contributors, occasional documentation editors, and engineers who rarely write docs won't install dedicated linting tools. If checking requires installation, they'll skip it.

Configuration files complicate simple workflows: Local linting tools need .vale.ini files, package installations, and directory structures. For a single file check, this complexity is unnecessary.

Installation issues waste time: Dependency conflicts, version mismatches, path problems, and platform-specific bugs turn "quick check" into "troubleshooting session."

Browser-based linting eliminates all these friction points. If you can open a web browser, you can lint markdown files with professional style guides—in seconds, with zero setup.

How browser-based markdown linting works

Modern web browsers support WebAssembly (WASM), which allows compiled programs to run at near-native speed directly in the browser. Vale, the prose linting engine, can be compiled to WebAssembly and run entirely client-side.

Here's what happens when you lint markdown in the browser:

Vale WASM loads once: The first time you visit the linting tool, Vale's WebAssembly binary loads and caches. This is about 6.2MB compressed and happens automatically.
Rule packages download on demand: When you select a style guide (Microsoft, Google, Red Hat, etc.), the rule package downloads and caches in your browser's storage. Future sessions use the cached version.
Linting runs locally: When you paste markdown content or upload a file, Vale processes it entirely in your browser. No server contact, no data transmission—just local computation.
Results display instantly: Issues appear with line numbers, explanations, and suggestions. Many issues include one-click fixes you can apply directly in the browser editor.
Everything stays cached: The WASM binary, rule packages, and your preferences persist in browser storage (IndexedDB and Cache API). Subsequent visits are instant, even offline.

The entire process runs locally on your device. Your markdown content never leaves your browser, ensuring complete privacy for sensitive or unreleased documentation.

Step-by-step: linting markdown with zero installation

Let's walk through the complete workflow from start to finish:

Step 1: Open the browser editor

Navigate to the ProseLint Web editor. No sign-up, no account creation, no installation prompts. The editor loads immediately with a clean interface.

Step 2: Choose your markdown input method

You have three options for getting content into the editor:

Paste directly: Copy markdown text from your local file and paste into the editor. This works for quick checks and small files.

Upload files: Drag and drop markdown files (.md, .mdx) onto the editor or use the file picker. ProseLint Web supports Markdown, MDX, AsciiDoc, HTML, and plain text.

Type in the editor: Start writing directly in the browser editor. Useful when drafting new content and you want real-time linting feedback.

Step 3: Select a professional style guide

ProseLint Web supports multiple professional rule packages. Choose the one that matches your needs:

Microsoft Writing Style Guide: Best for general technical content, product documentation, and enterprise writing. Comprehensive rules for clarity, consistency, and accessibility.

Google Developer Documentation Style Guide: Optimized for developer-focused docs, API references, and technical tutorials. Emphasizes conciseness and developer-friendly language.

Red Hat Documentation Style Guide: Designed for enterprise technical documentation, system administration guides, and detailed reference materials.

Elastic Documentation Style Guide: Focused on search and observability product docs, with rules tuned for technical accuracy and user guidance.

GitLab Documentation Style Guide: Open-source and DevOps-oriented rules for documentation in software development contexts.

Select the package from the dropdown. If it's your first time using that package, it downloads automatically (typically 1-3 seconds). Subsequent uses are instant.

Step 4: Lint your markdown

Click the "Lint" button. Vale processes your markdown and highlights issues directly in the editor:

Error-level issues appear in red with clear explanations
Warning-level issues appear in yellow for suggestions
Info-level messages provide optional guidance

Each issue includes:

Line and column number for precise location
Rule name and explanation
Suggested fix (when available)
Severity level (error, warning, suggestion)

Step 5: Review and fix issues

Navigate through issues using the issues panel:

Apply quick fixes: Many issues include one-click fix buttons. Click to automatically apply the suggested replacement.

Understand the rule: Read the explanation to learn why Vale flagged the issue. This helps you improve your writing over time.

Decide on actions: Some suggestions are context-dependent. You might choose to keep original phrasing when it's intentional or technically accurate.

Filter by severity: Focus on errors first, then warnings, then suggestions. Prioritize what matters most for your content.

Step 6: Copy or download corrected content

Once you've addressed issues:

Copy from the editor: Select all text and copy back to your local file. Maintain your local workflow without needing export features.

Keep the session: The browser editor autosaves your content in IndexedDB. You can leave and return to the same content later (privacy-focused: data stays local).

Supported markdown formats and features

Browser-based linting isn't limited to basic markdown. ProseLint Web handles sophisticated formats and features:

Markdown flavors

Standard markdown: CommonMark-compliant markdown with full syntax support
GitHub-flavored markdown: Tables, task lists, strikethrough, and GitHub-specific extensions
MDX: Markdown with JSX components for modern documentation frameworks
Markdown with frontmatter: YAML frontmatter in documentation and blog posts

Document features Vale understands

Code blocks: Vale ignores code snippets and focuses on prose content
Inline code: Backtick-wrapped code treated as literal text, not prose
Links: Link text checked for style, URLs ignored
Headings: Heading text linted while respecting heading hierarchy
Lists: Both ordered and unordered list items checked for consistency
Blockquotes: Quote content linted according to style rules
Tables: Table cell content checked, formatting preserved

Beyond markdown

The browser linting tool also supports:

AsciiDoc: Technical documentation format popular in enterprise contexts
HTML: Direct HTML content with prose extraction
Plain text: Raw text files without markup

Use cases for zero-install markdown linting

Browser-based linting fits into workflows where local installation doesn't make sense:

Quick README checks before GitHub commits

You've updated a project README and want to verify consistency before pushing. Open the browser tool, paste the markdown, lint with your preferred style guide, fix issues, and commit—no CLI installation required.

Open-source contribution quality checks

Contributing documentation to an open-source project? Many projects enforce style guides in CI. Use the browser tool to self-check before submitting pull requests, ensuring your contribution meets quality standards without setting up local Vale CLI.

Documentation review on the go

Working from a tablet, Chromebook, or computer without your usual development environment? Browser-based linting works anywhere you have a web browser, no local setup required.

Team member onboarding

New team members can check their documentation contributions immediately without going through Vale CLI installation and configuration. Share a link to the browser tool in CONTRIBUTING.md—anyone can use it instantly.

Client or contractor work

Writing documentation for clients on short-term projects where setting up full linting infrastructure isn't justified? Browser-based linting gives you professional quality checks without tool commitment.

Quick style guide exploration

Testing different style guides to see which fits your organization's voice? Switch between Microsoft, Google, and Red Hat packages in the browser tool without modifying local configurations.

Browser linting vs. local CLI tools: when to use each

Browser-based linting and local CLI tools serve different needs. Here's how to choose:

Use browser linting when you need

Quick, one-off checks without installation
Linting on systems where you can't install tools
Instant access without configuration
Privacy-guaranteed processing (content never leaves device)
Easy style guide comparison and testing
Simple workflow for occasional contributors

Use Vale CLI locally when you need

Automated linting in pre-commit hooks
CI/CD integration for pull request enforcement
Bulk linting across entire documentation directories
Custom rule development and testing
Integration with text editors (VS Code extension)
Team-wide configuration enforcement via .vale.ini

Many teams use both: browser tool for individual writers doing self-checks, Vale CLI in CI/CD for enforcement. This approach combines convenience for authors with automation for quality gates.

Privacy and security with browser-based linting

Running linting entirely in the browser has significant privacy advantages:

No data transmission: Your markdown content processes locally in your browser. Vale WASM runs client-side, not on remote servers. Network activity is limited to one-time downloads of Vale binary and rule packages—never your content.

Offline functionality: After initial loads, the browser tool works completely offline. Cache API and IndexedDB store Vale WASM and rule packages locally. No internet required for linting.

No account requirements: No sign-up, no authentication, no user tracking. Your writing sessions are anonymous and local.

Client-side storage only: Content autosaved in the editor uses browser IndexedDB, stored locally on your device. No cloud synchronization, no server storage.

This architecture makes browser-based linting ideal for sensitive content: unreleased product documentation, confidential technical guides, or any writing that can't be uploaded to third-party services.

Getting started in the next 60 seconds

Try zero-install markdown linting right now:

Open the ProseLint Web editor in a new browser tab
Paste this sample markdown (or use your own):

# Getting Started

This is a really really simple guide to help you get started.
We're going to walk through the steps.

## Installation

Simply download the software and install it on your machine.

Select Microsoft Writing Style Guide from the package dropdown
Click "Lint" and watch Vale identify issues like:
- "really really" (redundant intensifier)
- "simple" (unnecessary qualifier)
- "simply" (adverb that weakens clarity)
Click quick-fix buttons to apply suggested improvements

You just linted markdown with a professional style guide—without installing anything.

Conclusion: linting shouldn't require installation

The barrier between "I should check this" and actually checking it should be as low as possible. Installation, configuration, and local setup create friction that prevents quality checks from happening.

Browser-based markdown linting eliminates that friction. Open a browser, paste content, get professional feedback—in seconds, with zero installation. Whether you're working on a borrowed computer, contributing to open source, or just need a quick check before committing, zero-install linting makes quality accessible.

Try the ProseLint Web editor with your next markdown file and experience the simplicity of linting without installation overhead.

Resources

ProseLint Web editor — zero-install markdown linting in your browser
Vale CLI — local installation for CI/CD and automation
Vale packages repository — professional style guides
CommonMark specification — markdown standard reference