Use lowercase URLs

URL paths on the web are case-sensitive by specification in RFC 3986 (opens in a new tab). While many servers normalize case for you, inconsistent casing creates duplicate pages that split PageRank and often needs the same cleanup plan as canonical URL consolidation.

Code Example#

On Linux servers (used by most web hosts), /Products and /products are genuinely different URLs. Both may be served, indexed separately, and compete against each other:

https://example.com/Products/shoes     → 200 OK  ← duplicate
https://example.com/products/shoes     → 200 OK  ← canonical-url

Even on Windows/macOS (case-insensitive), Googlebot treats them as separate URLs.

Why It Matters#

Mixed-case URLs can create duplicate content. Search engines may index both /Product and /product as separate pages, splitting link equity and diluting rankings, which is why Google's URL structure best practices (opens in a new tab) still recommend simple, normalized paths.

Correct Pattern#

✅ https://example.com/products/running-shoes
✅ https://example.com/blog/how-to-pick-shoes
✅ https://example.com/about-us
 
❌ https://example.com/Products/Running-Shoes
❌ https://example.com/Blog/How-To-Pick-Shoes
❌ https://example.com/About-Us

Server-Level Fix#

Nginx:

# Redirect uppercase URLs to lowercase
if ($uri != $uri_lower) {
  rewrite ^(.*)$ $uri_lower permanent;
}

Apache (.htaccess):

RewriteEngine On
RewriteMap lc int:tolower
RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule (.*) ${lc:$1} [R=301,L]

Framework-Level Fix#

Next.js — next.config.js:

module.exports = {
  async redirects() {
    return [
      {
        source: '/Products/:path*',
        destination: '/products/:path*',
        permanent: true,
      },
    ]
  },
}

Express.js middleware:

app.use((req, res, next) => {
  const lower = req.path.toLowerCase()
  if (req.path !== lower) {
    return res.redirect(301, lower + (req.search || ''))
  }
  next()
})

Sitemap and Internal Links#

After enforcing lowercase URLs, audit with Screaming Frog (opens in a new tab) or an equivalent crawler:

1. XML sitemap entries — all <loc> values must be lowercase
2. Internal <a href=""> links — update any uppercase links
3. Canonical tags — <link rel="canonical"> must match the lowercase URL

Exceptions#

• Staging, utility, login, account, or internal search pages may intentionally use different crawl or index signals if they are not meant to rank.
• Temporary migration states can produce noisy intermediate signals; flag the live production URL pattern, not one-off transition artifacts.
• When redirects, canonicals, robots directives, or indexability signals conflict, fix the strongest final signal first instead of reporting every downstream symptom as a separate blocker.

Standards#

• Use these references as the standard for the final search-facing HTML, metadata, and crawl behavior.
• Check the implementation against Google Search Central: URL structure best practices before treating the rule as satisfied.
• Check the implementation against RFC 3986: URI syntax — case normalization before treating the rule as satisfied.

Verification#

Automated Checks#

• Inspect rendered HTML and HTTP headers to confirm the expected metadata or crawlability signal is present.
• Test the affected URL with Google Search Console or equivalent tooling where relevant.
• Re-crawl a representative page set after deployment.

Manual Checks#

• Confirm the change does not create conflicting canonical-url, robots, or structured-data signals.