To use WebPageTest, go to webpagetest.org, enter your URL, choose a test location, device and connection, run the test and read the waterfall, filmstrip and Core Web Vitals in the results. It is the most detailed free speed test for finding exactly which file slows a page. For a quick first check, use our free website speed test.
Key takeaways
- WebPageTest lets you choose test location, device, browser and connection speed.
- The waterfall shows every file and its timing. The filmstrip shows how the page looks as it loads.
- Run several test runs and compare, because single results vary.
- Some options may need a free account, so check what is available when you test.
What is WebPageTest?
WebPageTest is a free web performance testing tool used by developers to see how a page loads in a real browser. It gives more control than most speed tests, including where the test runs and how fast the simulated connection is. It is best when you need detail, not just a score.
How do you run a WebPageTest?
- Open webpagetest.org.
- Enter the full URL of the page to test.
- Choose a test location close to your main visitors.
- Choose a device and connection that matches your audience. A mobile device on a slower connection is a good start.
- Set the number of test runs, so you can compare more than one result.
- Start the test and wait for the results.
How do you read WebPageTest results?
Core Web Vitals and summary
The summary shows key metrics, including Largest Contentful Paint and layout shift. Good values are LCP of 2.5 seconds or less and CLS of 0.1 or less (Google, web.dev). See our Core Web Vitals test guide.
Waterfall
The waterfall lists every file in the order it loads, with timing bars. Long bars are slow files, and gaps show where the browser is waiting. Check large images and scripts first.
Filmstrip
The filmstrip shows screenshots of the page at set times, so you can see when content actually appears. It helps you judge how fast the page feels, not just how fast it loads.
First view and repeat view
The first view is a visitor with an empty cache. A repeat view shows how the page loads when files are already cached. A large gap shows caching is working.
How do you fix issues found in WebPageTest?
- Find the slowest or largest file in the waterfall.
- Compress oversized images. See how to optimize images for page speed.
- If the first request is slow, improve server response. See what a good TTFB is.
- Defer scripts that block the page. See render-blocking resources.
- Run the test again with the same settings and compare.
WebPageTest vs other speed tests
WebPageTest gives more detail but is more technical than PageSpeed Insights or GTmetrix. Use PageSpeed Insights for Google’s view and WebPageTest when you need to debug. Read our comparison of GTmetrix, PageSpeed Insights and WebPageTest.
Frequently asked questions
Is WebPageTest free?
You can run tests for free, and some features may need a free account or a paid plan. Check the site for current options.
Is WebPageTest better than PageSpeed Insights?
It is more detailed, not necessarily better. They answer different questions, so use both when needed.
Which test location should I choose?
Choose the location closest to most of your visitors.
How many test runs should I use?
More than one. Several runs show whether a result is typical or a one-off.
Can WebPageTest test mobile?
Yes. You can choose a mobile device and connection profile.
Conclusion
WebPageTest is the tool to use when you need to see exactly what slows a page down. Choose realistic settings, read the waterfall and filmstrip, fix one issue at a time and compare. Start with our free website speed test and use WebPageTest when you need the detail.
