Google treats the portion of a URL after the domain name as case-sensitive. Thus Google could index both domain.com/example and domain.com/EXAMPLE but combine domain.com/example and DOMAIN.com/example.
This matters because content management systems typically generate URLs from page titles and often retain capitalization, resulting in three problems for search engine optimization:
- Duplicate content. Google may index both versions of the URL if they serve the same content.
- Link equity splitting. Capitalized URLs with lowercase inbound links can split link equity, hurting the ranking of the primary version.
- Internal errors. Sites hosted on Linux servers (such as Shopify and, often, WooCommerce) will display a 404 error page for capitalized URL characters when users enter lowercase versions.
Most web crawlers (and Search Console) do not offer case-sensitive URL filters, making detection challenging. The best way to prevent them is to ensure your server redirects all versions of a URL to the desired version. Each of these could redirect to domain.com/url, for example:
- domain.com/URL
- domain.com/Url
- domain.com/uRl
Some content management systems will automatically redirect, but always check to confirm. Enter the three URL versions above in your browser. If all load the same version (usually lowercase), no further action is required. If any result in an error page, fix immediately.
Depending on the CMS, plugins and apps can help set up cross-site redirection rules. Software engineer Brian Love’s guide explains how to enforce lowercase URLs.
Choosing URLs
For SEO, there is no URL rule as long as all versions redirect to the preferred version. I like lowercase URLs for simplicity and ease of cross-site redirect setup, although some users prefer capitalized URLs for readability, branding, and ad performance.
Cross-site URL consistency will not produce material ranking increases. But it will help Google understand your site structure, improve crawlability, and clarify what’s indexed.
