Web performance Metrics
TTFB is a metric that measures the time between the request for a resource and when the first byte of a response begins to arrive.
It helps identify when a web server is too slow to respond to requests. In the case of navigation requests — that is, requests for an HTML document
###It will be green (good performance) if less than <700ms
Page weight describes the total number of bytes of a particular web page. A web page is comprised of specific elements and assets that can be rendered and viewed in a web browser
###Should be average to good if page weight from 4MB to 2MB.
Start Render Time (SRT), or Time To Start Render (TTSR), is the time it takes for the web page to display any asset for the user. Specifically, Start Render Time is the time it takes for the DOM to complete and the window load event.
###It will be green (good performance) if less than <750ms
Page speed refers to the entire time span, from sending an HTTP request to a server to the complete and final display of the web page on a browser.
###Average fully loaded site should be less than 11s
The First Contentful Paint (FCP) metric measures the time from when the page starts loading to when any part of the page’s content is rendered on the screen.
###It will be green (good performance) if less than <1.8 Second
Largest Contentful paint (LCP)
The Largest Contentful Paint (LCP) metric reports the render time of the largest image or text block visible within the viewport, relative to when the page first started loading.
###It will be green (good performance) if less than < 3 Second
Total Blocking Time is an important user-centric performance metric that compares the time amount of non-responsive and responsive time during the rendering phase of the web page.
###It will be green (good performance) if less than <600ms
Error Rate
Error Rate is a performance metric that tracks the percentage of request issues you have in relation to the total number of requests.
Peak Response Time
Peak response time (PRT) measures the longest response time for all the requests coming through the server
DNS Lookup Time is the time it takes a Domain Name Server to receive the request for a domain name’s IP address, process it, and return the IP address to the browser.
###The average DNS lookup time is between 20 and 120 milliseconds
Some tool lists which helps to find the above metrics data:
- Chrome Devtool
- https://www.webpagetest.org/
- Some monitoring tools like New Relics, Sentry or logrocket etc.
Reference Site link: https://web.dev/user-centric-performance-metrics/
