• The test location closest to your target audience provides the most accurate representation of your page load.
• Don’t compare these tools equally and wonder why your scores differ from tool to tool.
• Onload time may misrepresent the true load time of your page.
• Real browsers provide a better indication of your website’s performance.
• It’s important to understand how each tool works before relying on them for any sort of data or results.

It depends. We feel that the use cases for each tool can be broken down into the following categories:

Quick Checks

GTmetrix, Pingdom Tools, and PageSpeed Insights

Consistency/Historical Tracking

GTmetrix and WebPagetest

In-depth Analysis

GTmetrix and WebPagetest

SEO Check

PageSpeed Insights, GTmetrix, and Pingdom Tools

Fully Loaded Time

The point after the Onload event fires and there has been no network activity for 2 seconds. This ensures more consistency with tests.

Possible issues with using this event: This event fires only when a page completely stops loading content, including ads and below the fold elements. Your site might have loaded fast above the fold and be usable, however since the analysis is now waiting for the entire site to stop loading data, your reported Page Load Time might be longer.

Onload Time

When the processing of the page is complete and all the resources on the page (images, CSS, etc.) have finished downloading. The browser will trigger window.onload when this occurs.

Issues with using this event: Some elements of the page load may not make it in before this event fires – like JavaScript based image carousels – causing inconsistent page load times and inaccurate screenshots. It may also report faster page load times than actual.

Onload time may misrepresent the true load time

Due to network variances or the way the page was designed to load (eg. asynchronous loading), resources loaded after the browser triggered window.Onload may not make it into reports.

The result is a report that indicates the page loaded faster than it actually did. This means that the while the tool received a “page finished loading” trigger at onload, the actual user is still experiencing resources being downloaded.

Our preferred testing platform, GTmetrix now uses fully loaded time, which waits for 2 seconds of network inactivity before stopping the test.

The Other Platforms

GTmetrix and WebPagetest allow you to switch between Fully Loaded and Onload Time.

Pingdom defaults to Onload Time only.

This is why you may see Pingdom results loading faster than GTmetrix and/or WebPagetest.