1% of problems we won’t talk about here. None of this advice applies to you.
98% of “I have a slow WordPress site” problems:
Cache plugins will NOT speed up your website significantly.
The number of plugins will not effect your site speed.
Putting your site on a CDN will not speed up your site.
Slow shared hosting – This has nothing to do with WordPress per se. It’s just that there are many WordPress blogs on shared hosts and they are often slow. You can run any kind of website slowly on a shared host. Some companies like GoDaddy or BlueHost can have thousands of websites running on one physical system. The interesting thing is that high speed, cloud based servers on Amazon or Google are actually cheaper than shared hosts. Of course, you have to learn how to setup a server! So this is a funny issue because it isn’t really about WordPress, it’s more about the economics of computer systems and the economics of knowledge. Anyway, if you’re a human being raising your hand saying, “My WordPress website is slow” the answer to your problem is to learn how to setup a WordPress server, or hire someone who can. Your problem is you just don’t know how to do something simple. It’s like not knowing how to put gas in your car, and not understanding why it won’t move.
Improperly uploaded or linked images
The other 1% of WordPress speed problems come from improperly adding images. When you upload to the media library, dy default WordPress rescans the image into three different sizes. If you use a properly coded theme from the free repo, your theme will serve the correct image to the user.
Solution for 98%:
Properly upload images via the media uploader.
Simply pay for faster hosting.