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Home Guide 5 Critical Metrics that can help improve Site Speed

5 Critical Metrics that can help improve Site Speed

By Jash Unadkat, Technical Content Writer at BrowserStack -

Creating a good user experience for visitors accessing a website isn’t as easy as implementing a single proven formula. However, paying close attention to specific metrics at regular intervals can provide teams with a number of actionable insights. These insights help teams identify issues that may be worked on in order to improve site speed.

Five key metrics that teams must keep an eye on to ensure websites are delivering an optimal experience.

1. Time To First Byte (TTFB)

Time to First Byte represents the amount of time taken by a mobile or web browser to fetch the first byte of information or response from the server once a user requests a specific URL. At a high level, TTFB comprises of three components:

  • The time required to forward the HTTP request
  • The time taken by the server to process the request
  • The time taken by the server to send back the first byte of information to the user

Inefficiently written code, slow database queries, or a misconfigured server are among the most common issues that may lead to the poor performance of TTFB. Identifying and resolving such critical issues can considerably enhance website speed.

2. Transmission Control Protocol (TCP) Connection Time

In layman’s terms, TCP Connection Time represents the time taken by any browser (Mobile or Web) to establish a reliable connection with a server. Identifying issues in TCP connections can be challenging at times as it depends on multiple factors.

For instance, increased user traffic from actual users or bots can cause a spike in connection time. Also, users accessing a website from different geographic regions are likely to experience longer connection times. Teams must consider using a CDN or a caching server in such cases to improve website performance and to ensure that users are able to establish faster connections.

3. DNS Lookup Time

DNS stands for Domain Name System. Basically a domain name like “” needs to be mapped to an IP address. The DNS Lookup time can be defined as the amount of time taken by the DNS provider to translate a domain name into an IP address. If a web page is taking too long to load, there’s a high probability that the page has multiple DNS lookups.

For instance, a social sharing button (Facebook, LinkedIn, Twitter, etc) leads to additional DNS lookups on a particular page. This causes the page to load slowly. To solve this, teams must use a reliable DNS provider rather than using the free versions.

4. Page Load Time

Page load time represents the total amount of time taken by the browser to completely display the content of a particular web page. Listed below are a few factors that affect the page load time in this regard:

  • Inefficiently written HTML, CSS scripts
  • Usage of unoptimized high-resolution images
  • Multiple redirects

It’s highly recommended for teams to follow all the guidelines mentioned in this article on how to increase website speed so that they can create web pages that load faster.

5. Page Response Time

As the name suggests, page response time represents the amount of time taken to completely receive the first response from the target server. If the response time is low, there’s a high probability of users bouncing from the site. According to Google, the response time should be less than 200ms.

Must read: Why Page Speed Matters and How to Test your Page Speed Score

Keeping an eye on the metrics discussed above will help teams evaluate their websites for speed or performance issues at regular intervals. Teams should consider leveraging this free website speed test tool by BrowserStack to benchmark their scores against their competitors.

A unique offering of this tool is one can test the desired web page on a range of real devices and browsers (both mobile and desktop). This means users can instantly run tests for their web pages across a range of widely used device-browser combinations (For example Chrome on Samsung Galaxy Note10, or Safari on iPhone X).

improve website performance


improving site speed

improving site speed

Once the test execution is completed the tool provides extensive reports by collating data for all the metrics we discussed above. Refer to the images below to get a glimpse of the detailed reports representing data for all metrics.

Although maintaining an optimal user experience consistently is not an exact science, consistent focus on the metrics highlighted above and taking timely action to fix anomalies can help deliver great user experiences.

Website Speed Test

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