Developer Tools
ValidateHTML
HTML validation API and free online validator for deployed pages
ValidateHTML checks deployed web pages for HTML specification compliance, accessibility, meta tags, Open Graph cards and page weight through an API or free
Overview
The ValidateHTML homepage
ValidateHTML is a free set of online validators for HTML, CSS, XML, JSON and web accessibility. The HTML Validation API checks deployed URLs in CI/CD pipelines, fetching a page once and running five checks on that same response: accessibility, markup validity, meta tags, social cards and page weight. Results come filtered through false-positive work to provide one verdict your build can act on. An independent developer built and maintains the service, which uses specialized parsing engines for each standard and applies proprietary rules to determine which findings are reliable enough to report.
Capabilities
- Accessibility (WCAG) validation with machine-detectable failures
- HTML specification compliance checking
- Meta tags and viewport validation
- Open Graph checker
- Page weight measurement and compression analysis
- Single API endpoint with configurable checks
- Single verdict field for build pipeline integration
- Automatic AI-powered HTML fixes
- Weekly site audits with change notifications
- GitHub Actions integration
Pricing
Pricing model: Freemium
Free: unlimited validators and checkers, no account required, free site scans. Solo: 49 EUR per month including full site reports and monitoring of 1 site. Agency: 149 EUR per month including monitoring of 10 sites. Automatic fixes: from 3 EUR for 10 pages, 1 free fix daily without account. Full sit
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ValidateHTML fact sheet
| Community votes | 0 |
|---|---|
| Based in | Paris, France |
| Website | validatehtml.com |
ValidateHTML metrics
Vendor metrics for validatehtml.com: Ahrefs Domain Rating and Majestic link data, with the delta since the last review.
- Domain Rating
- 9
- no change since last check
- Trust Flow
- 10
- no change since last check
- Citation Flow
- 32
- no change since last check
- Referring domains
- 124
- no change since last check
- External backlinks
- 1,001
- no change since last check
Vendor Domain Rating (Ahrefs) checked 6 Nov 2026, spec changed 5 Nov 2026. Vendor topic: Business/Publishing and Printing (10). Vendor Majestic data checked 5 Nov 2026, spec changed 5 Nov 2026. Link metrics supplied by Majestic. Trust Flow, Citation Flow and Topical Trust Flow are trademarks of Majestic-12 Ltd.
ValidateHTML vendor domain
Open the vendor record
We read this from the registry's RDAP record on 5 Nov 2026, 18:50 UTC.
- Domain age
- 19 years
- Registered
- Expires
- Registrar
- NameCheap, Inc.
- DNSSEC
- Not signed
ValidateHTML post-launch report
| Measure | At launch, then latest |
|---|---|
| Domain Rating (Ahrefs) | 9 first measured 5 Nov 2026 |
| Trust Flow (Majestic) | 10 first measured 5 Nov 2026 |
| Referring domains (Majestic) | 124 first measured 5 Nov 2026 |
Day 0 since launch. Next receipt: day 30, 5 Dec 2026. Many things move these figures, so a change is not proof of cause. Only stored readings are shown.
About to launch?
Plan your launch with our free playbook, from preparing your listing to choosing more launch directories.
- The week before
- On the day
- Week one
- Beyond launch
Buyer questions
What is the difference between this API and html-validate?
This is not an API wrapper around html-validate. The library html-validate is free and better for validating files on disk. ValidateHTML adds orchestration: one deployed URL is fetched once and five checks read that same response, filtering findings through false-positive work, so you get one verdict your build can act on instead of parsing prose from five separate calls.
How many API calls does a free account get?
Every account gets 100 calls a month at no cost, which is enough to wire up a pipeline and see whether this belongs in yours. The allowance resets on the 1st and your account shows what it has spent.
What does the quality score measure?
The quality score ranges from 0 to 100 with letter grades A through F. It is based on the number of distinct issue types, not how many times each occurs. Each distinct error type multiplies the score by 0.85; each distinct warning type costs 3 points capped at 15 total, so best-practice advice can never drag valid code below a B.
Is the automated audit a compliance certificate?
No. Automated testing finds a real subset of accessibility failures and misses the rest. The monitoring page lists exactly what it cannot judge, and who should not buy it.
How long does it take to get a response to support inquiries?
ValidateHTML is built and maintained by an independent developer. Most emails are answered within 2-3 business days. Bug reports are prioritized.
Leave a review for ValidateHTML
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ValidateHTML has a free listing. The owner can unlock the full profile with a paid launch for $5:
- Founder story (locked)
- Milestones (locked)
- Demo video (locked)
- Dofollow website link (locked)
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