W3C_CSS_Validator
W3C •
Since 1996
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Official Docs
What is W3C_CSS_Validator?
The W3C CSS Validator is a free service provided by the World Wide Web Consortium (W3C) that checks Cascading Style Sheets (CSS) for compliance with W3C standards. This tool helps web developers ensure their CSS code follows proper syntax and best practices. The validator can check CSS by URI, file upload, or direct input. It's an essential tool for maintaining code quality and cross-browser compatibility. While modern browsers are forgiving of CSS errors, validation helps catch potential issues and ensures long-term maintainability.
User Agent String
Jigsaw/2.3.0 W3C_CSS_Validator_JFouffa/2.0
How to Control W3C_CSS_Validator
Block Completely
To prevent W3C_CSS_Validator from accessing your entire website, add this to your robots.txt file:
# Block W3C_CSS_Validator
User-agent: W3C_CSS_Validator
Disallow: /
Block Specific Directories
To restrict access to certain parts of your site while allowing others:
User-agent: W3C_CSS_Validator
Disallow: /admin/
Disallow: /private/
Disallow: /wp-admin/
Allow: /public/
Set Crawl Delay
To slow down the crawl rate (note: not all bots respect this directive):
User-agent: W3C_CSS_Validator
Crawl-delay: 10
How to Verify W3C_CSS_Validator
Verification Method:
W3C validator user agent
W3C validator user agent
Learn more in the official documentation.
Detection Patterns
Multiple ways to detect W3C_CSS_Validator in your application:
Basic Pattern
/W3C_CSS_Validator/i
Strict Pattern
/^Jigsaw/2\.3\.0 W3C_CSS_Validator_JFouffa/2\.0$/
Flexible Pattern
/W3C_CSS_Validator[\s\/]?[\d\.]*?/i
Vendor Match
/.*W3C.*W3C_CSS_Validator/i
Implementation Examples
// PHP Detection for W3C_CSS_Validator
function detect_w3c_css_validator() {
$user_agent = $_SERVER['HTTP_USER_AGENT'] ?? '';
$pattern = '/W3C_CSS_Validator/i';
if (preg_match($pattern, $user_agent)) {
// Log the detection
error_log('W3C_CSS_Validator detected from IP: ' . $_SERVER['REMOTE_ADDR']);
// Set cache headers
header('Cache-Control: public, max-age=3600');
header('X-Robots-Tag: noarchive');
// Optional: Serve cached version
if (file_exists('cache/' . md5($_SERVER['REQUEST_URI']) . '.html')) {
readfile('cache/' . md5($_SERVER['REQUEST_URI']) . '.html');
exit;
}
return true;
}
return false;
}
# Python/Flask Detection for W3C_CSS_Validator
import re
from flask import request, make_response
def detect_w3c_css_validator():
user_agent = request.headers.get('User-Agent', '')
pattern = r'W3C_CSS_Validator'
if re.search(pattern, user_agent, re.IGNORECASE):
# Create response with caching
response = make_response()
response.headers['Cache-Control'] = 'public, max-age=3600'
response.headers['X-Robots-Tag'] = 'noarchive'
return True
return False
# Django Middleware
class W3C_CSS_ValidatorMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
if self.detect_bot(request):
# Handle bot traffic
pass
return self.get_response(request)
// JavaScript/Node.js Detection for W3C_CSS_Validator
const express = require('express');
const app = express();
// Middleware to detect W3C_CSS_Validator
function detectW3C_CSS_Validator(req, res, next) {
const userAgent = req.headers['user-agent'] || '';
const pattern = /W3C_CSS_Validator/i;
if (pattern.test(userAgent)) {
// Log bot detection
console.log('W3C_CSS_Validator detected from IP:', req.ip);
// Set cache headers
res.set({
'Cache-Control': 'public, max-age=3600',
'X-Robots-Tag': 'noarchive'
});
// Mark request as bot
req.isBot = true;
req.botName = 'W3C_CSS_Validator';
}
next();
}
app.use(detectW3C_CSS_Validator);
# Apache .htaccess rules for W3C_CSS_Validator
# Block completely
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} W3C_CSS_Validator [NC]
RewriteRule .* - [F,L]
# Or redirect to a static version
RewriteCond %{HTTP_USER_AGENT} W3C_CSS_Validator [NC]
RewriteCond %{REQUEST_URI} !^/static/
RewriteRule ^(.*)$ /static/$1 [L]
# Or set environment variable for PHP
SetEnvIfNoCase User-Agent "W3C_CSS_Validator" is_bot=1
# Add cache headers for this bot
<If "%{HTTP_USER_AGENT} =~ /W3C_CSS_Validator/i">
Header set Cache-Control "public, max-age=3600"
Header set X-Robots-Tag "noarchive"
</If>
# Nginx configuration for W3C_CSS_Validator
# Map user agent to variable
map $http_user_agent $is_w3c_css_validator {
default 0;
~*W3C_CSS_Validator 1;
}
server {
# Block the bot completely
if ($is_w3c_css_validator) {
return 403;
}
# Or serve cached content
location / {
if ($is_w3c_css_validator) {
root /var/www/cached;
try_files $uri $uri.html $uri/index.html @backend;
}
try_files $uri @backend;
}
# Add headers for bot requests
location @backend {
if ($is_w3c_css_validator) {
add_header Cache-Control "public, max-age=3600";
add_header X-Robots-Tag "noarchive";
}
proxy_pass http://backend;
}
}
Should You Block This Bot?
Recommendations based on your website type:
| Site Type | Recommendation | Reasoning |
|---|---|---|
| E-commerce | Optional | Evaluate based on bandwidth usage vs. benefits |
| Blog/News | Allow | Increases content reach and discoverability |
| SaaS Application | Block | No benefit for application interfaces; preserve resources |
| Documentation | Selective | Allow for public docs, block for internal docs |
| Corporate Site | Limit | Allow for public pages, block sensitive areas like intranets |
Advanced robots.txt Configurations
E-commerce Site Configuration
User-agent: W3C_CSS_Validator
Crawl-delay: 5
Disallow: /cart/
Disallow: /checkout/
Disallow: /my-account/
Disallow: /api/
Disallow: /*?sort=
Disallow: /*?filter=
Disallow: /*&page=
Allow: /products/
Allow: /categories/
Sitemap: https://example.com/sitemap.xml
Publishing/Blog Configuration
User-agent: W3C_CSS_Validator
Crawl-delay: 10
Disallow: /wp-admin/
Disallow: /drafts/
Disallow: /preview/
Disallow: /*?replytocom=
Allow: /
SaaS/Application Configuration
User-agent: W3C_CSS_Validator
Disallow: /app/
Disallow: /api/
Disallow: /dashboard/
Disallow: /settings/
Allow: /
Allow: /pricing/
Allow: /features/
Allow: /docs/
Quick Reference
User Agent Match
W3C_CSS_Validator
Robots.txt Name
W3C_CSS_Validator
Category
other
Respects robots.txt
Yes
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