Friday, 21st Jul 2017

«

»

High Performance

The online website performance testing service WebPagetest is frequently used for measuring and analyzing the performance of websites.

Optimization Grades

At the top of the results page are a set of grades for the most critical performance optimizations. These cover the basic optimizations that apply to just about all sites and anything that isn’t an A or a B grade may justify further investigation and tuning.

First Byte

The First Byte time is the time from when the user started navigating to the page until the first bit of the server response arrived. The bulk of this time is usually referred to the “back-end time” and is the amount of time the server spent building the page for the user.

Keep-alive Enabled

Each request for a piece of content on the page needs to be made over a connection to the web server. Setting up new connections can take time so it is best to re-use connections when you can and keep-alive is the way that is done.

Compress Text

Just about everything on a page that isn’t an image or video is text of some kind. Text compresses well and HTTP provides a way to transfer the files in compressed form. Enabling compression for text resources can both improve the performance and reduce the costs of serving the content by reducing the amount of data transmitted.

Compress Images

The image compression check looks at photo images, images can usually be compressed substantially without any noticeable reduction in visual quality. It’s also not uncommon for other data to be included in photos, particularly if they came from a digital camera and that should be removed from images before being published to a web page.

Cache Static Content

Static Content are the pieces of content on your page that don’t change frequently. The user’s browser can store them in a cache so if the user comes back to the page they can use the copy they already have. Successfully caching static content in the user’s browser can significantly improve the performance of a repeat visit and reduces the load on the web servers.

High-level Metrics

The data table at the top of the results page gives you some high-level information about the page that was loaded:

First View

The First View row is a test that was done with a browser that had it’s cache and cookies cleared out and represents what a first-time visitor to the page will experience.

Repeat View

The Repeat View row is a test that was done immediately after the First View test without clearing out anything. The Repeat View test represents what someone will see if they are coming back to the page some time after visiting it the first time.

Document Complete

The metrics grouped together under the Document Complete heading are the metrics collected up until the browser considered the page loaded.

Fully Loaded

The metrics grouped together under the Fully Loaded heading are the metrics collected up until there was 2 seconds of no network activity after Document Complete.

Load Time

The Load Time is the time from when the user started navigating to the page until the Document Complete event (usually when all of the page content has loaded).

First Byte

The First Byte time is the time from when the user started navigating to the page until the first bit of the server response arrived. The bulk of this time is usually referred to the “back-end time” and is the amount of time the server spent building the page for the user.

Start Render

The Start Render time is the first point in time that something was displayed to the screen.

Requests

This is the number of requests that had to be made by the browser for pieces of content on the page.

Bytes In

This is the amount of data that the browser had to download in order to load the page. It is also commonly referred to as the “Page Size”.

Site last updated February 5, 2013 @ 10:02 am; This content last updated January 14, 2012 @ 4:57 pm