Advanced validator that extracts, merges, and validates HTML/CSS (including external styles) via W3C standards.
Users
180
+18 in 30 days
Rating
4.4 / 5
unchanged in 30 days
Ratings
5
0 in 30 days
Store rank
#66K
#56K among extensions
Version
1.5
updated 30 Aug 2026
Users
monthly, 8 months
Latest, 15 Oct 2026:180 usersMove the mouse over the chart for any month
Ratings count
monthly, 8 months
Latest, 15 Oct 2026:5 ratingsMove the mouse over the chart for any month
The Chrome Web Store rounds user counts down to the leading digit, so the user line moves in steps. The ratings count is exact and is the better signal of real adoption.
About HTML & CSS W3C Validator Pro
HTML & CSS W3C Validator Pro
Ensure your code meets World Wide Web Consortium (W3C) standards with a single click.
Developing clean, standards-compliant websites is essential for SEO, accessibility, and cross-browser compatibility. This extension streamlines the debugging process by sending your page's code directly to the official W3C Validators, eliminating the need for manual copy-pasting.
Unlike basic tools, this extension is built for the modern web: it handles dynamic DOM states, external frameworks, and complex stylesheets effortlessly.
🚀 KEY FEATURES
Advanced HTML5 Validation: Captures the current state of your DOM, including elements generated dynamically by JavaScript.
Smart CSS Validation (Pro): Overcomes CORS restrictions to analyze stylesheets that standard validators often miss.
Merge & Validate: Automatically fetches all internal and external styles (including CDNs like Bootstrap or Tailwind), merging them into a single block for a complete audit.
Used CSS Analysis: Focus on efficiency by extracting and validating only the rules currently affecting elements on your page.
Source Validation: Ideal for checking raw .css files or the direct page source in the browser.
👨💻 DEVELOPER-CENTRIC WORKFLOW
Official Standards: Direct integration with validator.w3.org and jigsaw.w3.org.
Visual Feedback: Provides immediate status indications and cursor updates while processing complex data.
Privacy-Focused: Built on Manifest V3 with no tracking or ads; your code is only sent to W3C servers for analysis.
Secure Execution: Utilizes safe fetching methods to protect user privacy while retrieving external assets.
🎯 IDEAL FOR
Web Developers: Identify unclosed tags, invalid attributes, and CSS syntax errors during production.
SEO Specialists: Ensure semantic markup is valid to improve search engine crawling.
Accessibility Experts: Verify code structure to maintain compatibility with screen readers.
QA Testers: Streamline technical audits for complex, framework-heavy applications.
Start writing higher-quality code today. Install HTML & CSS W3C Validator Pro.
Growth
Window
Users
Change
Ratings
Rating
7 days
+3
+1.7%
0
0.00
30 days
+18
+11.1%
0
0.00
6 months
+109
+153.5%
+1
−0.60
Chrome Web Store search rankings
Where HTML & CSS W3C Validator Pro appears when people search the store, with the 30 day change