Is the web browser performance rule “only 2 requests in parallel per hostname” still correct?

Question

In his book \"High Performance Websites\" Steve Souders wrote (2007) that browsers limit parallel requests to a domain/hostname to two at a time. Is this still valid today?<

Answer 1

Yes, there may be some variations, but that limitation is certainly still valid. Some browsers might allow more than two parallel requests to a host, but it's still only a few.

There may also be limitations on the server side. If you are requesting active pages, e.g. ASP/ASP.NET/PHP, they are usually limited to a single request at a time per user.

However, with bandwith increasing this limitation has a smaller impact than it had in 2007. Eventhough you can still only do a few requests in parallel, each request is faster so the limitation is not very noticable.