Optimizations to reduce website loading time

Question

What are some important optimizations that can be made to a website to reduce the loading time?

Answer 1

The first optimisation is: Decide if it is slow, and if not, don't bother.

This is trickier than it sounds, because it's not like testing a desktop app or game. A game is slow if when you play it on the target hardware, the frame rate is too low. This is very easy to measure.

A web site is trickier, because you, as the developer, are probably using a local test system with a very fast network. Even when you use your staging / system test servers, you're probably still on the local network. Even your production servers are in all likelihood, on the same continent.

The same is possibly not true for quite a lot of your users.

Therefore the options which exist are:

• Find out by asking your users, whether they find it to be slow
• Simulate a high latency environment and test it yourself (or your QA team)
• Guesswork

The latter is not recommended.

An option which the holier-than-thou Yahoo Web Sites performance book (which yes, is a book you can buy) doesn't mention a lot is HTTPS. Most web applications which handle important data run mostly or entirely over HTTPS, which changes the rules of the game rather a lot. Remember to do all testing with it enabled.