Which browsers we support
GOV.UK shares the same browser support matrix with GOV.UK Frontend for pages served to the general public.
If the application you are working on is aimed at internal users rather than the general public you should look at your analytics data and check which browsers your users are using. Then you can then make an informed decision about which browsers to test with.
For more information around browser support, see the Service Manual page about Designing for different browsers and devices.