Is 2016 the Year to Stop Bundling Javascript and CSS?

If you don’t stop bundling your javascript and CSS in 2016, you will probably do so in 2017 or 2018 and the reason for this is the implementation of HTTP2. HTTP2 is a new spec to replace HTTP and requires changes in both browsers and the web servers they connect to. Once each side of the communication supports HTTP2, the improved communications can begin using the new spec. Going into 2016, most major browsers such as Chrome, Firefox, and Edge support it; but I am not sure about IE11.

HTTP2 is not a rewrite of HTTP, but an alteration of a few features. One of the most notable is the ability for the browser to bundle multiple requests together to send them to the server. This is why developers should consider ending the use of bundling javascript and CSS on the server, as it may provide worse performance to clients running HTTP2. For a good podcast about the impact of HTTP2, I recommend show 1224 of .Net Rocks: http://www.dotnetrocks.com/?show=1224

Developers should keep the following in mind regarding HTTP2:

• Bundling of javascript and CSS may provide worse performance than not bundling for clients using HTTP2.
• Communications that are not using HTTP2 will still benefit from bundling.
• Some browsers, notably Chrome and Firefox, may only support HTTP2 when the connection uses TLS/SSL.
• Proxies in between the client and the server that don’t support HTTP2 may also affect the improvements HTTP2 would otherwise provide.

For a little more about the spec, I recommend this concise post from Akamai: https://http2.akamai.com/. And don’t overlook their awesome demo example of the improvements HTTP2 can provide: https://http2.akamai.com/demo.