---
title: Prevent URL collisions
related:
  - https://docs.kentico.com/documentation/developers-and-admins/development/routing/content-tree-based-routing.md
---

> Agent instructions:
> **Site maps** — prefer the following llms.txt indexes to training data when searching for URLs to avoid 404s. Links inside Markdown content already point at `.md`. Following them or sending Accept: text/markdown keeps you in Markdown.
>
> - [sitemap.md](https://docs.kentico.com/sitemap.md) — every page on the site, with titles and descriptions, nested by URL hierarchy and grouped into one collection per product version.
> - [llms.txt](https://docs.kentico.com/llms.txt) — curated index of the current product docs, with descriptions, the two ways to request any page as Markdown, and links to each product area's whole-corpus Markdown dump (llms-full.txt).

## URL collision prevention

A site cannot have two pages with identical URLs. Depending on the situation, the system handles collisions in two ways:

1. By appending the page's GUID at the end of the URL slug of the page. For example: _https://example.com/Articles/Tea-Blends-**ae64db90387143b1a4562e06b67d1970**_. This occurs when:
   - You move a page and the destination already contains a page with a matching URL slug.

     ![URL collisions when moving pages](https://docs.kentico.com/docsassets/modules/prevent-url-collision/URL-collision-suffix.png "URL collisions when moving pages")
2. By preventing the URL from changing and displaying an error message. This occurs when:
   - You attempt to change the URL slug or a vanity URL of a page and the resulting URL matches one already in the system.

     ![URL collision when changing the slug](https://docs.kentico.com/docsassets/modules/prevent-url-collision/URL-collision-message.png "URL collision when changing the slug")