So this post was initially created for myself, so I could remember all the really good and helpful testing tools. As it became a good resources I changed it a bit and and added more details to make it super useful for everyone.
When working on optimizations it is always good to know where you started and where you get to, that way you can measure the improvements and gains you have made. Or perhaps can learn what not to change.
Below are the tools that I commonly use to get a before and after snapshot to see the improvements.
Here is a list of tools for Testing WordPress Speed, Performance and Code Optimization.
This is a great tool and has a cool retest feature. To use this feature, copy the URL of your before or initial test, make your changes, run a 2nd GTMetrix test then click the compare button and paste the URL from your first test. You are now presented a page where you can easily tell what changes have been made.
They also have a Pro Version. the pro version gets you priority in running your tests and can run from about $15/month to $150/month. When you pay money you can monitor more sites,
Steven Johnson, a WP Hosting Reviews senior editor, works from Atlanta and covers all things related to WordPress and Hosting.
He graduated from Georgia Tech in Chemical Engineering, has managed hosting companies and now builds WordPress and Joomla Websites for small to medium companies full time.