Google     PageSpeed      Insight

1   

It provides PageSpeed score and suggestions to make web site faster.

    GTmetrix      

2   

Easy to use through its clean user interface.

    WebPage Test      

3   

Testing tool that runs speed tests from multiple locations around the world.

    Pingdom      

4   

With Pingdom you can monitor your websites' uptime, performance, and interactions for a better end-user-experience.

    UpTime      

5   

Trusted by thousands of websites to check  page speed, owntime,and domain health.

   DareBoost      

6   

It provides a quick visual overview of website performance and page loading speed.