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Viewport
What does this page do at a phone width, right now?
Every responsive preview that scales the page with a CSS transform is lying: media queries resolve against the real viewport, so a transformed 1440px page at 30% is a desktop layout drawn small. These are real iframes at real widths, which is the only arrangement where a breakpoint answers the way it will answer on the device.
Reach itPress ⌘+K on any tab and type viewport.Ctrl+Kon Windows and Linux
TWO BUILDS9 browsers
Chromelisting in reviewFirefoxlisting in reviewBravelisting in reviewOperalisting in reviewEdgelisting in review4 moreChromium browsers: Arc, Vivaldi, Chromium, Opera GXthe Chrome buildin the panel · free, no counter
What this actually is
side-by-side frames at genuine device widthsWhen a layout has to be checked at several widths at once, and any time a scaled preview has told you something you could not reproduce on a phone. Not a substitute for a real device on anything touch-dependent.
Asked about this tool
4 of themWhy is the frame not scaled to fit?
Because scaling the width is what makes a preview lie. The height is scaled and the width is not, so every media query in the document resolves against the number written on the frame.
Do clicks in one frame really happen in the others?
Yes, and they travel as a selector rather than as coordinates - the same button is at a different place in each frame, which is the entire reason to have several open.
Can it preview a page that refuses to be framed?
No. A site sending `X-Frame-Options: DENY` or a restrictive `frame-ancestors` cannot be put in an iframe by anything, and the frame says so rather than showing an empty box.
Why are the device widths not the numbers on the spec sheet?
Because a phone advertised at 1170 pixels reports 390 to CSS. The presets are CSS pixels throughout, which is the number a media query is written against.
TWO BUILDS9 browsers
Chromelisting in reviewFirefoxlisting in reviewBravelisting in reviewOperalisting in reviewEdgelisting in review4 moreChromium browsers: Arc, Vivaldi, Chromium, Opera GXthe Chrome build63 of these · no host permissions · three free audits