Viewport

Ship text that fits
every screen

Textproof catches overflow, line-wrap drift, and font-size issues before your users do. Run it against any live page.

What it catches

Verifies text layout across 9 breakpoints (375px–1920px) using real DOM measurement

⚠️

Overflow Detection

Finds text bleeding outside containers at any breakpoint — especially mobile where it matters most.

↔️

Line-Wrap Drift

Compares line counts across viewports to catch unexpected reflows that break your layout.

📏

Responsive Sizing

Suggests clamp() values that keep text readable from the smallest phone to the largest monitor.

Text bugs textproof catches

These elements have real layout issues — textproof flags them automatically

Unbreakable Long Heading That Overflows On Mobile Devices

This heading uses white-space: nowrap with a long string — guaranteed overflow on small screens.

Fixed 42px Font Size Without Responsive Scaling

No clamp(), no media queries — this text clips at every mobile breakpoint.

Excessive Line-Wrap Drift Example

This paragraph intentionally uses a larger font size that causes significant line-wrap drift between desktop and mobile viewports, demonstrating how textproof detects reflow problems that aren't visible at a single breakpoint.

Results from this page

Textproof catches overflow, line-wrap drift, and clipping across all breakpoints.

FAIL
nowrap heading overflows at 375px, 412px, 430px
FAIL
42px heading clips inside container on mobile
WARN
Large paragraph drifts +3 lines on iPhone SE
PASS
Hero H1 — fits all breakpoints with clamp()

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View Interactive Report

Why textproof uses real DOM instead of pretext math →