Use lowercase URLs
SkillFiles & storageLowercase is a skill for auditing URL structure and configuring routing on a new site. It guides an agent through checking for uppercase letters in URLs, setting up 301 redirects to lowercase equivalents, and normalizing incoming URL case in server or framework configuration. It applies to any ser
Available today. Use it from your connected AI after setup.
No other account needed.
Have a site whose URLs, routes, and sitemap can be inspected, and access to its server configuration or framework router.
Then ask your AI: use the Use lowercase URLs skill
What your AI can do with it
- Scan internal links and server-side routes for URLs containing uppercase letters
- Check HTTP response codes to confirm uppercase variants return 301 redirects, not 200
- Configure server or framework routing to normalize incoming URLs to lowercase
- Add 301 redirects from existing uppercase URLs to their lowercase equivalents
- Check the sitemap for uppercase <loc> entries
- Review route definitions and framework router configuration for URL case handling
Getting started
- Have a site whose URLs, routes, and sitemap can be inspected, and access to its server configuration or framework router.
- Add the skill to the agent's available skills.
- Ask the agent to audit the site's URLs for uppercase letters and test whether uppercase variants redirect with 301.
- Follow the skill's fix guidance to normalize URL case in the server config or router and update internal links and sitemaps.
- Consult references/rule.md for implementation details and framework-specific guidance.
What this skill tells your AI
The instructions your AI receives, as published by thedaviddias/front-end-checklist in skills/lowercase/SKILL.md and read by ahel’s review.
Mixed-case URLs can create duplicate content—search engines may index both /Product and /product as separate pages, splitting link equity and diluting rankings.
Quick Reference
- URLs should be entirely lowercase to prevent duplicate content issues
- Most web servers treat /Page and /page as different URLs, creating duplicates
- Redirect uppercase and mixed-case URLs to their lowercase equivalents with 301
- Apply lowercasing in your server config or framework router, not ad hoc
Check
Scan the site's internal links and server-side routes for URLs containing uppercase letters. Check HTTP response codes for uppercase variants of key URLs to confirm whether they redirect (301) to lowercase.
Fix
Configure your server or framework to normalize all incoming URLs to lowercase before routing. Add 301 redirects from any existing uppercase URLs to their lowercase equivalents. Update internal links and sitemaps to use only lowercase URLs.
Explain
URL case matters for SEO because case-sensitive servers treat /Page and /page as different resources, creating duplicate content. Even on case-insensitive servers, inconsistency confuses crawlers and splits PageRank across URL variants.
Code Review
Scan the site's route definitions, server configuration, and internal links for uppercase letters in URL paths. Test key URLs in uppercase and mixed case — verify they return 301 to the lowercase version, not 200. Check the sitemap for any uppercase entries. Verify framework router is configured to normalize URL case.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/seo/lowercase
Signals
- GitHub stars
- 74k
- Forks
- 7k
- Last commit
- Aug 2026
Questions
- When should this skill be used?
- Use it when auditing URL structure or configuring a new site's routing. It applies to any server or framework that allows case-insensitive file systems; Linux servers are case-sensitive by default.
- Why do URL case and SEO matter together?
- Case-sensitive servers treat /Page and /page as different resources, so search engines may index both as separate pages, splitting link equity and diluting rankings. Even on case-insensitive servers, inconsistency can split PageRank across URL variants.
Advanced
- Item type
- skill
- Key
lowercase- Source
- github.com/thedaviddias/front-end-checklist