Browser Viewport

Trivia: why we built this

The same HTML you write has to survive a 14× width range — from 280px (a Galaxy Fold, closed) to 3840px (a 4K display). That's one codebase, one set of CSS, stretched across screens so different they barely belong in the same category.

Stranger still: "mobile" didn't only get bigger. The Fold's cover screen at 280px is narrower than the original iPhone's 320px. The smallest screen you must support today is smaller than the one that started the whole responsive era.

Chrome DevTools shows you one of those widths at a time. So checking five breakpoints means looking at five pictures minutes apart and comparing them from memory — and memory is exactly where layout bugs hide. You don't notice the 20px that shifted; you notice it when a client does.

So we put them side by side. One tab, every width, scrolling and clicking in sync.

Bonus: four viewports in one tab used ~35% less RAM than the same site in four tabs — the iframes share one renderer.

Live at the chrome store: https://chrome.google.com/webstore/devconsole/d059f9b8-a529-4181-91d8-8ee07011591b/mpimhljihcmpgcafdmgbmonjnpfhokie/edit

Preview any page on every screen size.Try it now — free!

Quick use cases

• Responsive QA before shipping — catch a broken breakpoint on Galaxy Fold or iPad without resizing the window 10 times

• Client demos — show a site working on their phone, laptop, and office monitor in one screen share

• Design handoff review — compare the built page against the mockup at every breakpoint at once

• Checking a full flow, not just the homepage — click through nav → pricing → checkout with all viewports following along

• Form testing — type once, see the layout, validation errors, and keyboard behavior on every size

• Legacy support checks — confirm the site still works at 1024×768 or on an old netbook

• Ultrawide & 4K sanity — spot hero images that stretch or text lines that run too wide

• Competitor teardown — load any public site and study how their responsive layout adapts

• Bug reproduction — "it's broken on mobile" → find which width actually breaks it in seconds

• Before/after comparisons — reload after a CSS fix and verify nothing regressed elsewhere

Had shipped the stable version in the chrome web store!

https://chrome.google.com/webstore/devconsole/d059f9b8-a529-4181-91d8-8ee07011591b/mpimhljihcmpgcafdmgbmonjnpfhokie/edit

Had shipped the stable version in the chrome web store!

https://chrome.google.com/webstore/devconsole/d059f9b8-a529-4181-91d8-8ee07011591b/mpimhljihcmpgcafdmgbmonjnpfhokie/edit

See your site on phone, tablet, laptop, desktop and big screen at once — in one tab. Every viewport is a real browser frame at true device size, so layouts behave exactly as on the real thing.

• 17 devices across phones, tablets, laptops and desktops — toggle any on or off

• Synced scrolling — scroll one, all follow, matched by position so different page heights stay aligned. Or Solo mode.

• Synced clicks — click a link or button in one viewport and every device follows, even when it's hidden in the ☰ menu on mobile

• Synced typing — type once and the text fills in on every device. Works with React/Vue forms, checkboxes and dropdowns.

• Drag cards to rearrange, rotate to landscape, hide what you don't need

• Zoom to Fit, or 25–100%

• Remembers your devices, order and zoom between sessions

• Light and dark theme

• No frameworks or dependencies — uses less memory than opening the same site in four tabs

Just added the ability to do simultaneous sync actions across all viewports.
Clicking / Typing / Form Changes / Scrolling