HTML Validator
FreeValidate HTML markup for W3C compliance
About HTML Validator
Browsers are forgiving, which is exactly why broken HTML can ship unnoticed until it confuses a screen reader, trips up a crawler, or renders differently across devices. The HTML Validator from ToolHub by Codaiman checks your markup against W3C rules so you can catch unclosed tags, misnested elements, and invalid attributes before they cause real problems.
Paste a full page or a fragment and the tool parses it, reporting errors and warnings with enough detail to locate each issue in your source. Cleaner markup means better accessibility, more predictable rendering, and fewer surprises for SEO crawlers. It works entirely in the browser, requires no account, and gives instant feedback, keeping your code on your machine while you tidy it up at no cost.
Common uses
- Checking a landing page for compliance issues before launch to improve accessibility and SEO
- Finding the unclosed or misnested tag responsible for a layout breaking unexpectedly
- Validating an HTML email template fragment for stray or invalid markup
- Reviewing CMS or template output to catch invalid attributes and deprecated elements
- Confirming generated or hand-written HTML follows W3C standards during a code review
How to use
- 1
Configure options
Set your preferences using the options panel below.
- 2
Click Generate
Click the process button to generate your result instantly.
- 3
Copy or download
Copy the result to clipboard or download it directly to your device.
Why ToolHub?
- Instant error detection
- Detailed error messages
- Standards compliant
FAQ
Does it follow W3C validation rules?
Yes. The tool checks markup against W3C standards and reports errors and warnings consistent with those rules.
Can I validate a fragment, not just a full page?
Yes, you can check partial markup such as a template snippet, though a complete document gives the most thorough results.
Does it check linked CSS or JavaScript?
No. It validates the HTML structure itself. Use the CSS Validator and JavaScript Validator for those languages.
Is my HTML sent to a server?
Validation runs in your browser, so your markup stays on your machine and is not stored.
Can I use HTML Validator on mobile?
Yes — ToolHub is fully responsive and works on iPhone, Android, tablets and all modern browsers. No app install needed.