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SweepLens and Prism

Find every width where your layout breaks.

Five device sizes miss the bugs in between. The sweep widens your page from 320 to 1920px in 10px steps and reports each range where it breaks, the element responsible and a screenshot at the worst width.

Sweep a page freeSee plans
161
widths per page
10px
steps, 320–1920
~1 min
per page
A real UICheck check running: every screen size is tested, then the breakpoint sweep checks every width from 320 to 1920px and finds two ranges where the page scrolls sideways
Found: 780–820px, 184px too wide

Why sweep

Bugs live between the device sizes

Testing at 390, 768 and 1280px says nothing about 800px, the width of many small tablets and split-screen laptops. Layouts break where one media query ends and the next hasn’t started yet.

What five sizes see

What the sweep sees

Two broken ranges, both between the standard sizes.

What you get

Everything you need to fix it

The usual fix

Let it shrink instead of adding another breakpoint

Most broken ranges come from a fixed width. A max-width, a minmax() column or a min-width: 0 usually fixes every width at once.

/* Before: fits at 768px, breaks at 800px */
.banner { width: 940px; }

/* After: fits every width */
.banner { width: 100%; max-width: 940px; }
.grid   { grid-template-columns:
          repeat(auto-fit, minmax(min(260px, 100%), 1fr)); }

How it works

One switch, 161 widths, every breakpoint

No setup and no code access. The sweep runs after the screen sizes on Lens and Prism.

  1. Step 1

    Paste a URL

    Any live or staging page, on any stack: WordPress, Next.js, React or plain HTML.

    Start free

  2. Step 2

    Sweep 320 to 1920px

    The page is widened 10px at a time and every width that scrolls sideways is recorded.

    See how it works

  3. Step 3

    Fix the ranges

    Each broken range with the element responsible and a screenshot at its worst width.

    Read the fix guide

Questions

What is a breakpoint tester?

A tool that checks a page across a range of screen widths rather than a few devices, to find the widths where the layout breaks.

How many widths does the sweep test?

Every 10px from 320 to 1920px: 161 widths in one run, usually in under a minute per page.

What does it look for?

Anything that makes the page wider than the screen: fixed-width banners, tables, images, embeds and rows that don’t shrink. For each broken range you get the element responsible, how far it sticks out and a screenshot at the worst width.

Does it run on every page of a full-site check?

On the first 10 pages, after the screen sizes. It doesn’t change the score; it’s extra information about where to look.

Which plans include it?

The breakpoint sweep is part of Lens and Prism.

Stop guessing where it breaks

Lens is $5 a month: the breakpoint sweep, every screen size, Safari and Firefox, and full-site checks.

Start freeSee pricing