Website developers who want to increase traffic and user retention should not only optimize user performance, but also pay attention to specific performance metrics. What are the most important metrics, and how can they be estimated?

Before you start, you should find out how your website performs in various parts of the world. A properly chosen CDN must ensure equally high speed in all target regions. Consistency is important for delivering perfect user experience, so you need to make sure visitors are accessing the same end product.

Since so many features affect website performance, web masters use “multivariate testing” method to estimate website metrics over time.

Website Speed Performance Metrics

To get the results of many metrics for some certain website you can perform a speed test on webpagetest.org. The results will be based on the summary of page performance values (for more detailed metrics you will need to download the raw page data report). Pay attention to the following aspects:

1. 1. Time To Title. The amount of time between the moment an end user requests the site and the moment when it’s shown up in the browser (only title is displayed). It is defined by delivery speed from the main server to user’s browser. Additionally, there’s Time To Start Render (when the content appears on the page) and Time to interact (when a user can scroll the page and click on links).


2. 2. DNS Lookup Time – the amount of time for DNS provider to turn a domain name into an IP address.


3. 3. Connection Time shows the period between a request and establishment of a connection between the main server and user’s browser. It may depend on many factors (traffic, presence of bots, geographic regions) and you can upgrade your infrastructure to improve this metric and store assets in CDN cache.


4. 4. Time to First Byte – the time for the 1st byte of data to reach user’s browser. Some slight improvements of code can improve this metric, and you should separate static and dynamic content for users to wait less. Server misconfigurations should also be eliminated.

Content Complexity

To evaluate website performance better, you should understand many other factors including complexity of website content.

5. 5. Overall Weight is the total volume of bytes the user receives. The relationship between assets is also important, and even one heavy asset can slow page down. While you’re continuing to expand your site, get rid of unnecessary assets. Waterfall analysis will help you to identify categories of heavy assets and alter or remove them.


6. 6. Total Asset Count that includes JavaScript, CSS, etc.


7. 7. Third-Party Domains are used when widgets or videos are embedded on website. But if such domain fails, it may cause downtime.

User Behavior

Now you need to find out what users do after clicking to your website.

8. 8. Error Rate. Compare the number of requests to error rate. If this value is affected by the number of concurrent users, test website performance under different loads. You will be ABLE TO PREPARE for traffic surge and minimize issues later on.


9. 9. Bounce Rate shows how often users leave your website without exploring it. “Single page sessions” affect SEO and may be frequent because of poorly implemented keywords, slow loading or unattractive graphic design.


10. 10. Top Pages can help you to find out what content retains audience and keeps people engaged. Also pay attention to page shares via social media.


11. 11. Conversion Rate is another crucial factor that is calculated by dividing the number of visitors by the number of conversions. If this rate is lot, you might attract not appropriate traffic, or have insufficient call to action.