Skip to main content

Transition technical glossary

Posted by: , Posted on: - Categories: Transition

Here's a glossary of technical terms you might come across during the transition to GOV.UK.

AKA domain

An ‘AKA domain’ creates a parallel version of a site (or domain) for our redirection software so we can check redirects are correct before we put a site live.


In the Transition Tool, ‘archive’ is a link to a page on GOV.UK with the option of either viewing the old page on The National Archives site or going to the new organisation’s GOV.UK homepage.


The ‘canonical’ list has all duplicates removed and creates a single version of mappings to work on.


The Domain Name System (DNS) connects domain names (eg with a server address. The switchover itself happens when the DNS entries for your site are changed to point at our servers, enabling our servers to redirect or show archive pages.


A domain name (eg is used to reach a site. One or more domains can be used for a single site. Sub-domains are domains in their own right.

Friendly URLs (FURLs)

A customised URL designed to be easily memorable to direct people at a specific page with a simple title, eg These are not picked up in log files so we need to know about these in advance.

Global redirect

All pages on a site are pointed to the same place.


Requests for a URL or document.


In this context, a host or hostname is the same as a domain name.


Mappings are created from each URL of sites that are moving to GOV.UK, to make sure users are not confronted with broken links. A mapping either redirects people to new pages on GOV.UK that meet the same user need or presents a link to view the old content on The National Archives. This means that any URLs indexed by Google and other search engines, links from other websites and bookmarks all continue to work after transition.

You create, edit and manage mappings in the Transition Tool.

Partial transition (domain)

In some situations it isn’t possible to switch an entire site over at once. This can happen in several situations:

  • multiple organisations share a site
  • some content on a site needs to remain available at that site


This is the part of a URL after the domain name. For example, in the URL, the path is: /government/organisations


This is the first part of a URL, either http or https.

Query parameters

A query parameter might appear in some URLs. It’s the part of a URL written to be read by a computer, for example:

 In order to reduce the number of mappings for you to write and maintain, we identify the significant query parameters in use on your site, which lets us de-duplicate many URLs. A query parameter is significant if changing it means a user sees different content.


A redirect means automatically taking a user from the old URL they requested to the new one identified in the mapping. For example redirects to


Usually the smallest unit of transition. Note that one or more domains can be used for a single site, often for historical reasons.

(HTTP) Status codes

Examples of HTTP Status Codes are: 404, 410, 301, 200 and 502. In transition there are a few which are important. 301 is used for a redirect, 410 is used for archive, and 404 means that there isn’t a mapping for the old URL yet.


Subdomains are domain names which have a parent domain name. For example: and are different subdomains of their parent domain


The National Archives is the government organisation responsible for creating archives of UK government websites to maintain the public record in the digital age. The Transition Tool provides users with a link to TNA to view archived pages on transitioned sites.

TNA Timestamp

The National Archives Web Archive will produce snapshots (or “crawl”) of a given website, which are labelled with timestamps, for example 20100202072553 is for a snapshot taken on the 2 February 2010 at 07:25:53.


Time To Live. This is the number of seconds for which a DNS record can be cached by your computer, for example, before being checked with a DNS server. We ask for the TTL for your sites to be lowered to 5 minutes before switchover so that there is a clean cut-over - rather than different users getting the old or new site until the change has propagated. Commonly, TTLs can be set to a day, which would lead to poor user experience as they would see the old or new site unpredictably.


A URL is how a web browser requests pages, images and other data from a website.


Redirect. These are labelled green in the Transition Tool.


Archive, labelled grey in the Transition Tool.


Not found, labelled red in the Transition Tool. If this is returned after switchover, this means there is a missing mapping.


Note: post updated May 15, 2014 with more information about mappings.

Sharing and comments

Share this page