Is the HTML, CSS and JavaScript validator free to use?

Yes. The makeCSS.com Code Validator is 100% free with no signup, no account, and no usage limits. You can validate HTML, CSS, JavaScript, or full mixed documents directly in your browser.

Can I paste a full HTML document with CSS and JavaScript into the validator?

Yes. Auto mode accepts a complete HTML document and automatically splits embedded HTML, CSS, and JavaScript into separate analysis categories. The validator can also detect mixed full-page code even if you accidentally paste it into the HTML, CSS, or JavaScript tab.

What kinds of problems does the validator detect?

The validator checks for common HTML, CSS, and JavaScript mistakes such as unclosed tags, invalid attributes, malformed selectors, missing CSS syntax, suspicious values, brace mismatches, JavaScript syntax errors, DOM API typos, and other practical code issues.

Can I inspect only HTML, CSS, or JavaScript issues after validating a full page?

Yes. After validation you can switch between entire-code results and filtered HTML, CSS, or JavaScript issue lists. The upper code tabs and lower result filters stay aligned so you can inspect the extracted code and the matching issues together.

Does the validator work on mobile devices?

Yes. The validator is responsive and works on desktop, tablet, and mobile devices. On smaller screens the layout stacks vertically so you can still paste code, validate it, and review issues comfortably.

Is my code uploaded to a server?

No. Validation runs locally in your browser. Your code is not sent to a server, which makes the tool fast and convenient for quick checks while prototyping or debugging.

Free HTML Syntax Checker, CSS Syntax Validator & JavaScript Error Checker

Code Input

Paste your HTML code below and click Validate to check for errors.

Validation Results

Issues found in your code are listed below with line numbers and descriptions.

Waiting for input

Errors 0

Warnings 0

Language HTML

No results yet. Paste code and click Validate.

Free Online HTML Syntax Checker, CSS Syntax Validator & JavaScript Error Checker

The makeCSS.com Code Validator is a free browser-based HTML syntax checker, CSS syntax validator, and JavaScript error checker for common front-end mistakes, structural issues, and practical debugging problems. It is designed for developers, designers, students, and anyone who wants a fast way to validate front-end code without installing anything.

Why this validator is different

One validator for all three front-end languages – Check HTML, CSS, and JavaScript from a single interface.
Auto mode for full pages – Paste a complete HTML document with embedded <style> and <script> blocks and the tool splits and validates each part separately.
Mixed-code protection on every tab – If you accidentally paste a full page into the HTML, CSS, or JavaScript tab, the validator can still detect and split the content automatically when appropriate.
Per-language result filters – Switch between entire-code results and filtered HTML, CSS, or JavaScript issue lists.
Clickable issue reports – Click an error or warning to jump directly to the corresponding line inside the code editor.
Syntax highlighting with line numbers – Review your input in a readable, VS Code-inspired editor view.
Examples included – Load built-in sample code for HTML, CSS, JavaScript, or mixed Auto validation scenarios.
Free and local – No signup, no account, and validation runs directly in your browser.

What it can detect

The validator is tuned for practical front-end mistakes: unclosed HTML tags, malformed attributes, missing accessibility basics like alt, CSS property and value problems, missing punctuation, suspicious CSS values, JavaScript syntax errors, brace mismatches, common DOM API typos, and other mistakes that often appear while prototyping or debugging. If you need an HTML checker, CSS checker, or JavaScript validator in one place, this tool is built for exactly that workflow.

How to use the Code Validator

Paste your code into Auto, HTML, CSS, or JavaScript.
Click Validate to analyze the current input.
Review the Errors and Warnings counters at the top of the results card.
Use the lower result tabs to inspect Entire Code, HTML, CSS, or JavaScript issues separately.
Click any issue row to jump to the corresponding line in the editor.

This makes the validator useful for quick bug hunting, teaching, debugging broken snippets, checking generated code, and reviewing full single-page HTML documents with embedded styles and scripts.

Frequently Asked Questions

Is this HTML syntax checker, CSS validator, and JavaScript error checker free?

Yes. The makeCSS.com Code Validator is completely free, requires no signup, and can be used as often as you like.

Can I validate a full HTML document with embedded CSS and JavaScript?

Yes. Auto mode is built for full mixed documents. The validator splits the page into HTML, CSS, and JavaScript segments and reports issues per category.

What if I paste the full code into the wrong tab?

The validator is designed to handle that. If a full mixed document is pasted into the HTML, CSS, or JavaScript tab, the tool can detect and split it automatically during validation so the right issues still appear in the right categories.

Does the validator show separate HTML, CSS, and JavaScript results?

Yes. After validation you can switch between combined results and per-language issue filters, which is especially helpful when validating full documents in Auto mode.

Does the validator work on mobile?

Yes. The validator is responsive and can be used on mobile phones and tablets as well as desktop browsers.

Is my code sent to a server?

No. The validation runs in the browser, which makes the tool fast and convenient for checking snippets and full documents locally.

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