With around 2 million page views a month, our website is the primary platform for us to deliver high quality data to inform the UK, improve lives and build for the future. Therefore, it’s essential that our website is performant, reliable, and gives our users the information they need, when they need it and in the way they want it.
Our busiest time is at 7am when we publish our popular market sensitive releases – we usually see about 50,000 hits a minute. The code of practice for statistics requires that “statistics should be available to all users at the same time” so we must ensure our website can meet demand. To do this, we cache our website content and explain here why we do it, the different types of caching and how to make sure your browser downloads our releases at the time of publication.
The different types of cache
Caching our website content ensures that all users can get the latest release as close to the publication time as possible. A round trip to our servers for the release would reduce the response time and introduce unnecessary server requests – once published, the release content is static, so we use a Content Delivery Network (CDN) to take a copy of the content and serve it to browsers.
By using a CDN, our content is cached closer to our end users on geographically distributed servers, allowing quicker download of the release and the files which make up the web pages. Browsers on end user devices also use caching. Every time a user visits a webpage, the browser downloads everything on that webpage - HTML, JavaScript, stylesheets, images etc. To speed up the time it takes to display the page again, the browser caches everything it downloads by saving a copy of the files on the device. Browsers store these files until their time to live (TTL) expires or users manually clear their browser cache (TTL tells the browser how long to cache the content before downloading it again).
At the time of release
We can only update the CDN at the point of release and until then, the CDN will have a copy of the pre-release page. To do this we need to clear the CDN cache to force it to load the new release page. This is currently done manually, and we’ll soon be introducing an automated clear to further reduce the time taken.
To make sure you get the content promptly, forcing your browser to refresh the cache it holds for the page will make sure it downloads and displays our latest release. Here’s how to do it.
How to clear local browser cache
Clear cache for current page
Windows:
- Hold down Ctrl and Shift and then press ‘R’ key (Chrome, Edge, Firefox)
- Hold down Ctrl and Shift, and then press the Refresh button (Chrome, Edge)
- Hold down Ctrl and press the F5 key (Chrome, Edge, Firefox)
Mac OS:
- Hold down ⌘ Cmd and Shift, and then press ‘R’ key (Chrome, Firefox)
- Hold down Shift and click the Reload button (Chrome, Firefox)
- Hold down the Option + ⌘ Cmd key and then press the ‘E’ key (Safari)
Clear all browser cache (not just current page)
Windows (Chrome, Edge)
- Press the keys Ctrl, Shift and Delete (alternatively can be accessed via Settings and Privacy menus)
- Choose ‘Delete browsing data’
- Only check the ‘Cached images and files’ option
- Choose a time range e.g. last hour
- Choose ‘Delete data’
Windows (Firefox)
- Press the keys Ctrl, Shift and Delete (alternatively can be accessed via History and Clear Recent History menus)
- Only check the ‘Cache’ option
- Choose a time range e.g. last hour
- Choose ‘Clear now’
Mac OS (Chrome)
- Press the keys Ctrl, ⌘ Cmd and Delete (alternatively can be accessed via Settings and Privacy menus)
- Choose ‘Delete browsing data’
- Only check the ‘Cached images and files’ option
- Choose a time range e.g. last hour
- Choose ‘Delete data’
Mac OS (Firefox)
- Press the keys Ctrl, ⌘ Cmd and Delete (alternatively can be accessed via History and Clear Recent History menus)
- Only check the ‘Cache’ option
- Choose a time range e.g. last hour
- Choose ‘Clear now’
Clear cache on mobile devices
iOS (Safari)
- Open Settings on your mobile device
- Go to Apps and tap Safari
- Tap Clear History and Website Data
- Choose a time range e.g. Last hour
- Tap Clear History
Android (Chrome)
- In the Chrome app on the right of the address bar, tap More
- Tap Delete browsing data.
- Choose a time range e.g. Last hour
- Tap Delete data
We’d love to hear more from users of our services so that we can keep you updated and to learn more about your needs. If you’d like to stay up to date, please subscribe to this blog. You can submit feedback through our feedback form
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