Responsive HTML Preview

Paste HTML, choose or enter a viewport width, inspect the sandboxed rendering, and compare source statistics without uploading the markup.

HTML source

Viewport width

Custom width (px)

Scripts

390 pxPreview width

0Source bytes

0Source lines

0Source tags

Viewport approximationThis changes the iframe CSS width. It does not emulate device pixel ratio, browser chrome, mobile browser quirks, installed fonts or real touch/input behavior.

Width testing is not device emulation

The preview changes the sandboxed iframe CSS width so responsive layouts can be checked quickly. Device pixel ratio, platform fonts, browser UI and touch behavior are not emulated.