> For the complete documentation index, see [llms.txt](https://claycms.gitbook.io/clay/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://claycms.gitbook.io/clay/clay-data-structures/uris.md).

# Uris

## What is a Uri?

A uri is binding between a publicly accessible url and a specific [page](/clay/clay-data-structures/pages.md) in your Clay instance. When your browsing the web you're generally navigating between human-readable URLs like [www.vulture.com/movies/](http://www.vulture.com/movies/) or [www.thecut.com/2018/08/baby-squirrel-attack-germany.html](https://www.thecut.com/2018/08/baby-squirrel-attack-germany.html). But when you're creating and editing pages in Clay you're normally dealing with page instances with random ids, like [www.thecut.com/\_pages/cjko0bdjj008qi5ye57e00qyk.html](https://claycms.gitbook.io/clay/clay-data-structures/www.thecut.com/_pages/cjko0bdjj008qi5ye57e00qyk.html). This is where uris come in. 

*Uris are a bridge between a public facing url and a specific page instance*. When a page is published a public url for the page is determined ([see "Publishing" in Amphora docs](https://claycms.gitbook.io/amphora/basics/publishing)), and when that happens a uri is created. 

## Anatomy of a Uri

A uri is the most simple data structure in Clay and follows the following pattern: `domain.com/_uris/:id`

The `:id` value for a uri is a *base64 encoded string of a public url **without the scheme***. For example, if we're trying to find the uri that for [https://www.vulture.com/movies/](https://claycms.gitbook.io/clay/clay-data-structures/www.vulture.com/movies), we must simply base64 encode the  url without `https://` and we'll be able to find the specific uri: [`www.vulture.com/_uris/d3d3LnZ1bHR1cmUuY29tL21vdmllcy8=`](http://www.vulture.com/_uris/d3d3LnZ1bHR1cmUuY29tL21vdmllcy8=)

If you follow that uri above, you'll see that it's value is simply a text string which points to a specific page, thus forming a bridge between a public url and a specific page instance. 

## Redirects in Clay

But what happens if a page is published and then edited in such a way that changes the public url? Amphora handles the redirects for you! 

If Amphora finds that a previously published page's public url is changing, a redirect will be made. Internally Amphora is changing the original uri to point to a new uri for the new public url. When a user requests the old url, Amphora will respond with a `301` status and redirect the user to the new url. Handling this internally allows editors to iterate on their content without already shared links losing their content.

## Request Lifecycle For Public Routes

When a request for [www.vulture.com/movies/](https://claycms.gitbook.io/clay/clay-data-structures/www.vulture.com/movies) comes into Clay, the following happens:

1. The url is base64 encoded without the scheme of the request, this forms the `id`of the uri.
2. A lookup for the specific uri is performed.

   a. If it's a page instance, proceed

   b. If it's another uri, redirect and restart the process

   c. If it doesn't exist, send a `404` 
3. Proceed to compose the page and render it in the requested format