We’ve recently updated the Service Manual guidance to help developers across government identify and test performance issues before they become a problem for users.

It’s part of an ongoing effort to make sure GOV.UK is as inclusive as possible. Research by Google in 2016 found 53% of users abandoned a mobile site if it took more than 3 seconds to load. For government, GOV.UK is often the only place a user can get information. If the website were to perform badly, we become a single point of failure.

Knowing more about our users

To help people get what they need from GOV.UK as quickly as possible, we need to understand the context and environments our users are in.

Different devices

Not all users can afford high-end devices and we’ve found cheaper devices with entry-level hardware already struggle with today’s web. We regularly assess what devices and browsers people use to access GOV.UK so we can make sure our frontend works effectively on all of them.

Varying connectivity

Even if a user does have a modern device, connection speeds across the UK vary.

While the UK average broadband speed in 2018 was 18.57 Mbps there can be a substantial variation in the speed of internet connections. For example, even residents in London, a city with global connections and infrastructure, can have poor internet connections. In so-called ‘not-spots’, residents have reported connection speeds as slow as 0.26Mbps.

There are also users who cannot even rely on their mobile data coverage in these situations as 15% of indoor spaces in the UK have no data coverage.

And, even if a user can get data coverage, lots of people in the UK are often excluded from accessing websites because the pages have lots of assets, which causes them to load and run slowly. By compressing assets we can reduce the data transfer needed and better serve users with low connectivity and older devices.

Data use can be expensive

In addition, Ofcom statistics show the average monthly mobile data plan in the UK costs £18.36. This plan gives users 1.9GB of data per month. Considering the median mobile page weight is almost 1.7MB, this data allowance does not stretch far over this time period.

By reducing the size of webpages we can improve the data consumption and associated battery life of the user’s device.

User stress

On top of this, poor website performance can increase a users stress level and damage their productivity. A study by Glasgow Caledonian University found that participants had to concentrate 50% more when trying to complete a simple task on a website using a slow connection. This extra concentration needed to perform a task led to an increase in overall stress levels.

When GOV.UK is the only place our users can get government information and services, slow web performance is unacceptable.

What we’re doing to improve performance

As well as providing guidance on how developers across government can improve the performance of their frontend work today, we’re also looking at wider technology choices for all GOV.UK frontend development that will help in future.

To do this, we’re running a series of investigations to find out what technologies have a significant impact on web performance so we can prioritise future work.

We’ve previously discussed our work on font loading, and we’re also looking into strategies such as:



using HTTP/2, which is now supported by all major browsers to optimise asset delivery to users’ devices

updating fonts, for better overall compression to reduce data usage

applying modern compression methods, such as Brotli , to reduce the size of our pages

We plan to blog about our findings as the investigations progress and will update our frontend performance guidance as we learn more. In doing so, we hope developers across government can learn from what we’ve started and help us identify what to research next.

Performance is everyone’s responsibility

Web performance can mean the difference in someone being able to get what they need from government or abandoning their task completely.

Performance is therefore an integral part of the service we provide and every member of a service team should be involved in the optimisation process. Even minor changes can make a huge difference for our users.