Every width from a small phone to a full HD screen.
See your website at 375, 440, 768, 1280, 1440 and 1920 pixels wide at once, each marked with its Tailwind or Bootstrap breakpoint. Free, no account.
By Suraj KumarUpdated 3 min read
A layout tends to break between the sizes you checked. The screen size tester shows your site at six widths at once, from a 375 pixel phone to a 1920 pixel desktop, each with the breakpoint it falls in.
Six widths, side by side.
Open the screen size tester, type your site's address and press Show it at each size. An iPhone SE, an iPhone 17 Pro Max, an iPad mini, two laptops and a desktop show it at 375, 440, 768, 1280, 1440 and 1920 pixels wide.
Each title says the breakpoint its width is in, Tailwind's or Bootstrap's, as their documentation gives them. To find the very width a layout breaks at, add a size of your own and drag its corner: the breakpoint changes as you drag.
What it shows, and what it does not.
It shows layouts: widths, heights, orientation and the media queries that follow them. The browser drawing them is yours, so touch, the user agent and the pixel density are this browser's; check those on a real device. A site that refuses to be shown inside another page stays blank.
Nothing goes through KeepSimp.
Your browser loads the site straight from its own address, and KeepSimp has no server in between, so it never sees your site, its address or what is on it.
Further reading
Topics: screen size tester · screen resolution tester · test website different resolutions · viewport sizes · breakpoint tester · responsive breakpoints
A little less theory. A little more doing.
Try it on your own terms, with a free browser tool.
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