HTML Linter

A fast HTML linter and formatter for developers to catch syntax errors and enforce consistent styling across projects.

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1,104+

Total Calculations Run

< 15ms

Browser Execution Speed

100%

Client-Side Privacy

4.9 / 5.0

User Satisfaction

Worked Example & Common Values

Below is a sample worked calculation demonstrating how HTML Linter processes input data instantly inside your browser.

Sample Input Minified string: {"id":1,"status":"active","roles":["admin"]}

Computed Result

{
  "id": 1,
  "status": "active",
  "roles": [
    "admin"
  ]
}

Execution Mode Client-Side In-Browser JS

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About This Tool

The HTML Linter Formatter analyzes HTML source to detect syntax errors, unclosed tags, duplicate attributes, and deprecated patterns. It targets front-end developers, QA engineers, and dev teams who integrate code quality checks into local work, pull requests, or CI pipelines.
Conceptually, the tool tokenizes the input, applies a configurable rule set, and aggregates findings into a structured lint report. It ships with a sensible default for HTML5, while offering strict or loose modes to match project standards. Formatting is applied where possible to enforce consistent style.
Key features include configurable rules, line-length checks, indentation control, auto-fix suggestions for formatting, multi-file analysis, and exportable reports. The lint_report includes errors, warnings, and precise locations (line and column) to guide fixes.
Beneficiaries include development teams, code reviewers, and auditors seeking to speed up review cycles and ensure consistent markup. Unique value lies in real-time feedback, comprehensive rule coverage, and a clean, machine-readable output designed for CI integration.

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How to Use

Provide inputs: paste the HTML source into html_input and set optional configuration (rules, max_line_length, indent_style, indent_size).
Choose linting rules: default, strict, or custom configuration via the rules input.
Run analysis: trigger the linting process to produce a structured lint_report.
Review outputs: inspect errors, warnings, and suggested fixes with line and column locations.
Apply fixes or export: apply auto-fixes if enabled and export the report for CI or code reviews.

Frequently Asked Questions

Find Quick Answers

What does this tool detect?

It detects HTML syntax errors, unclosed tags, duplicate attributes, deprecated elements, mis-nested tags, and formatting deviations; it also flags accessibility concerns such as missing alt attributes and improper heading order.

Can it auto-fix?

Yes, auto-fix can adjust indentation, attribute ordering, whitespace, and simple tag closures. More complex structural issues may require manual edits. Auto-fix results are returned as fixed_html when requested, along with a patch-ready lint_report.

Which standards are supported?

The tool emphasizes HTML5 compliance with WCAG-related accessibility checks. It handles common templating patterns used in React, Angular, or server-side templates, but may require additional rule configurations for non-HTML syntax.

CI integration?

The tool exports a structured lint_report suitable for CI, supporting JSON output, logs, or patch diffs. Configuration can be stored in a project file to enforce consistent checks across environments.

Need to run multiple calculations?

Create a free account today to unlock unlimited daily runs, access advanced parameters, save your history, and request custom features.

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