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Countdown to switchover

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In February, UK Visas and Immigration (UKVI) moved the now defunct UK Border Agency website to GOV.UK.

Over the course of moving hundreds of sites, we have encountered all manner of glitches and problems so we have distilled what we learned into a simple, step-by-step process. UKVI is one of the largest agency websites in traffic terms but another smaller site, the Skills Funding Agency, moved on the same day, both following the same process.

Each time we move a site, we learn more so we can iterate the process to run as smoothly as possible for the agencies and arm’s length bodies moving to GOV.UK. This post outlines the high-level technical steps involved in redirecting a site.

The checklist

A successful move to GOV.UK depends on sharing the right information at the right time and knowing exactly what is transitioning. To do this, the transition technnical team creates a checklist for every site moving to GOV.UK which allows us to gather the critical information we need and decide the best way to redirect your site. It also clearly states who does what on both sides to make sure of a smooth and successful transition on the day. Talk to your transition manager about the checklist for your site.

We need to know the full list of domains and sub-domains for your site. Most importantly, we need to understand if there is anything staying behind. Some tools and transactions will need to function on old domains after transition, so it’s vital that we get this list right. A common blocker in previous transitions was the last-minute discovery of a sub-domain or tool.

Many organisations create friendly URLs and have existing redirects set up on their servers and we need to know about all of these to make sure they continue to work.

One of the biggest challenges we’ve faced in previous transitions is identifying the person who has responsibility for a site’s DNS configuration. On the day of switchover, it is this person who will actually make the transition happen, so it’s vital that we know not just who they are, but also who their back-up is. The checklist will include contact details for all the main technical people on both sides.

DNS and domains

When we transition a site, the DNS configuration of your site is changed to point the transitioning domain, eg, at the GOV.UK servers. Before we switch all the traffic to GOV.UK, we also need to make some DNS changes so we can make sure that the old sites can be mapped correctly to the new pages. I’ve written about this in a previous blog post.

For medium to large sites, the first change we make is to create ‘AKA’ and ‘old’ domains for all the domains and sub domains which are transitioning. AKA domains allow us to mirror the traffic on your site so we can test all the redirects before we go live. You can set up ‘old’ domains if you still want to access your site for a time after switchover.

For example for, we set up There are going to be different combinations of AKA domains we need to set up depending on the list of domains and subdomains you send us.

For smaller sites this approach is not necessary as it is possible to manage the transition manually. Your transition manager will be able to tell you if it’s necessary to set these up.

No big bang

The other vital ingredient of a successful transition is to publish your new GOV.UK content as it is completed. This, in combination with the AKA domains we put in place, means you can start mapping your old site in the Transition Tool.

It is impossible to make a smooth transition to GOV.UK if you publish everything at the last minute as you will have no time to map your content properly. From bitter experience we know that the end result of this approach is huge numbers of error pages and, worst of all, frustrated users.

You can access the tools to review and test mapping and archive links on your site’s dashboard page in the Transition Tool.

Full or partial transition

Most sites that move to GOV.UK will be what we call a ‘full transition’. This means that once new content is in place and mapped from the old site, we point the DNS for your site at GOV.UK’s servers which redirects all the site’s traffic to the new pages.

For some organisations, though, there are tools and transactions that are staying behind, so we need to make sure that these continue to work. The simplest approach to dealing with these is to move them to a new subdomain, for example,

If this is not possible, we will come up with an alternative “partial transition” approach which will use the AKA domains we have already created. The approach to transition will be determined once we have established the full list of domains and subdomains that are transitioning as we work through your checklist.

We will publish a more detailed post on partial transition soon.

Preparing for go-live

Before the day of transition, we will confirm again contact details for the person on the agency side who will actually make the DNS changes. When the date is confirmed, the first thing they will do is lower the Time to Live (TTL) to 300 (5 minutes). This needs to happen in advance, so if TTL is currently set to 2 days, it needs to happen 2 days before switchover.
Lowering the TTL means that within 5 minutes of the site switchover, everybody will see the GOV.UK site rather than a cached version of the old site.

After go-live, we then raise it back up to your department’s standard level (usually 24 hours).

On the day

By the day of the switchover, we will have completed work on mappings and tested all the redirect and archive links. This will give us the confidence to switch the traffic from the old site to GOV.UK.

At the agreed time, whoever is responsible for DNS on the agency side changes the DNS for the agency’s domain to point at the GOV.UK servers. This will be the same configuration as the AKA domains we have already set up.

Further information

If you need to understand the technical aspects of transition in more detail, talk to your technical team or your transition manager at GDS. We’ve also drawn up a glossary of technical terms for transition.

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