Responsive Viewport Tester

Tool #402 · OneFreePlace Developer Tools

Multi-viewportSmart stress labBreakpoint intelligencePrivate-first

Test setup

A responsive demo page is loaded so every feature works immediately. Replace it with your HTML or a URL anytime.

Upload HTML or drop a file here

HTML source safe inspectable mode

Run local scripts visual-only sandbox

Block remote assets private mode

Public URL

URL mode uses normal browser iframes. Sites can legally block embedding with frame-ancestors or X-Frame-Options. Local HTML mode remains fully inspectable.

Preview suites

Detected CSS breakpoints · click one to add −1 / exact / +1 panes

none yet

Add a viewport

Width

Height

Name

Synced testing

Scroll

Clicks

Inputs

Hover

Interaction sync and DOM audits work in safe local mode. By default, safe mode strips scripts, event handlers, meta refresh and remote asset requests. Turn remote assets on only when the preview needs them. Scripted local mode and public URL mode are visual-only sandboxes.

Debug overlays

8px grid

Outlines

Stress lab

Issue heatmap

RTL stress

200% root text

Hide media

Stress modes are intentionally destructive previews for inspectable local HTML. Reload/reset returns the source to normal.

Workspace

Stored only in this browser.

Scale

Responsive audit

QA score is a OneFreePlace heuristic, not a standards certification.

Run the audit to check each inspectable viewport.