SpeedLab
Guide for using SpeedLab and getting insights from test results.
Introduction
SpeedLab measures your website speed on a wide range of browsers & devices to give you a comprehensive view of website performance. Our goal is to help our users deliver a great end-user experience across browsers & devices.
Using the report
Browsers and Devices
Browsers and devices are carefully chosen to provide comprehensive coverage of end-user experience using major browser engines, high-end & low-end mobile devices, and multiple screen resolutions.
Test settings
SpeedLab parallelly loads the page on real browsers and mobile devices from our data centers in Western Europe connected to high-speed cable networks.
Mobile score & Website score
Score for mobile website & desktop website is calculated based on performance across all browsers or devices. Score is generated on a scale of 0 to 100, where 0 is the worst, and 100 is the best possible score.
Metrics & definition
SpeedLab uses navigation timing API which accurately measures time on browser to sequentially load the page. To know more about navigation timing API, click here.
Below are definitions of metrics and how they are calculated:
Page load time: Time taken from start till page is fully loaded. It is calculated as loadEventEnd - navigationStart.
Browser processing: Time take after browser starts processing page content till page is fully loaded. It is calculated as loadEventEnd - domLoading.
DNS: Time taken to lookup website domain. It is calculated as domainLookupEnd - domainLookupStart.
TCP: Time taken to establish a connection with server. It is calculated as connectEnd - connectStart.
TTFB: Time taken to receive the first response byte from server. It is calculated as responseStart - requestStart.
Response: Time taken to fully receive first reponse. It is calculated as responseEnd - responseStart.
DOM processing: Time taken after browser starts processing page content till page content is loaded. It is calculated as domComplete - domLoading.
Onload: Time taken by browser to execute javascript code after page content is fully loaded. It is calculated as loadEventEnd - loadEventStart.
Frequently Asked Questions
Why are there variations in my score?
While we try to ensure a consistent environment across test runs, there may be some variations in the score. These can be caused due to factors such as network variability, web-server variability, browser non-determinism, and more.
How can I improve the score for desktop website or mobile website?
For desktop websites, page load times less than 2100 ms across browsers score 90 or above. For mobile websites, page load times less than 1500 ms across devices score 90 or above.
My test ran on a different set of browsers and/or devices. How will this impact the report?
We ensure that tests are run on browsers and devices which meet our carefully chosen criteria to provide you comprehensive coverage on major browser engines, high-end & low-end mobile devices and device resolutions.
Need help
If you need further help, want to share feedback or report issues, reach out to us on support@browserstack.com.