Update our browser support strategy

[querkmachine]

What

We're looking to move to a graded system for defining the support received by the different browsers out there. This system will define not only in which browsers features run, but also the level of testing we intend to do with them and the priority we'll give to bugs.

Why

Currently Frontend uses specific versions of particular browsers to determine the minimum level of browser support and what polyfills/prefixes are needed: principally Internet Explorer 8 and Safari 9, which indirectly provide support for older versions of 'evergreen' browsers.

As we transition into reducing support for IE11, and dropping all supporting for IE8–10, we want to reassess how we decide how our minimum level of browser support will work in a world where we only (or mainly) support evergreen browsers.

Who needs to work on this

Developers, content designers

Who needs to review this

Developers, content designers

Done when

Tasks

Beta Give feedback

1. For each JavaScript component, document all possible levels of progressive enhancement (by browser support) #3227
   javascript +1
2. For each JavaScript component, document which ECMAScript version is required for each feature #3292
   javascript +1
   
3. Finalise browser support table and get feedback #3511
   +0
4. Update internal browser support documentation #2623
   documentation javascript +2
   

[querkmachine]

I started writing a document (internal only) positing various methods that we could determine future browser support.

[stevenjmesser]

We've unpacked the work needed to come to a decision on future browser support. It's kept in a Trello board which isn't open, but we'll add discrete actions to the team board.

[36degrees]

Main things left to do:

• Understand how browser support applies to CSS
• Review the existing draft and see if we can simplify it at all – see if rationale can be split out into a decision record / the PR
• Move browser support details from README to frontend docs and update

[romaricpascal]

README details are within the Browser and assistive technology support section

GOV.UK Frontend supports:

• recommended browsers and Internet Explorer 11
• recommended assistive technologies
• Internet Explorer 8, 9 and 10, although components may not look perfect
• your users overriding colours in Windows, Firefox and Chrome

[36degrees]

Gonna call this done!