Viewport Mentioned in the Test is not honoured in the result

When I ran a test with specifying a viewport of 1280 x 1024 or 1920 x 1200 in the script/Browser Dimensions. I found the final screen shot size after the entire page load is 600 x 351.


How are we actually ensuring the viewport mentioned in test script is set while running the test?

In my local setup with WPT code base v21.07.1, I faced the same issue. While submitting a test the viewport was set to1280 x 1024 by using setViewport Command.

Final Screenshot sizes:

Run 1: First View: 1264 x 911 Repeat View: 1264 x 891.
Run 2: First View: 1264 x 891 Repeat View: 1264 x 891.

From my understanding, for the viewport mentioned in the test, we add the margins.json data and we spun up a browser so that pixels drop is neutralized with the added margin.json values. And the margins.json x, y values for that browser is calculated after completion of each run for both first and repeat view. The default agent screen size is 1280 x 1024

The default agent screen size is increased to 1920 x 1200(AWS m5.xlarge). Even with this high value I am facing the same issue.

I see latest Code base is providing the maximum browser dimension as 1920 x 1200 from UI. I couldn’t find the screen size of your agents from

I am facing this issue on Windows agents. Is webpagetest only running tests on linux? And I am using AWS instances for agents.

Can someone provide insights how can we fix this issue?