Stop testing one breakpoint at a time

Synced viewports

See phones, tablets, and desktops at once, in a row or wrapped into a grid.

Interaction sync

Clicks, hovers, typing, and navigation mirror across every viewport in real time.

Scroll sync

Scroll one frame and every frame follows, including scroll areas inside the page.

Live CSS editing

Edit CSS across viewports, including media queries. Rule changes save locally and restore when you return.

Site breakpoints

Reads the breakpoints from the page's own stylesheets and builds matching viewports in one click.

Breakpoint inspector

Hover any element to see which of its styles change at every breakpoint.

Device presets

Add viewports from popular phone, tablet, and desktop presets, or define custom sizes.

Mobile spoofing

Phone and tablet viewports identify as touch devices, so touch menus, carousels, and components behave like they do on device.

Workspaces

Save viewport sets as named workspaces and switch between projects in one click.

Rotate & resize

Flip any viewport to landscape or drag its edges to test the widths in between.

Screenshots

Capture a clean screenshot of any viewport in one click.

Overflow warnings

Any viewport whose content spills past its width gets flagged automatically.

Dark mode switches

Force light or dark on any single viewport and check both schemes side by side.

MCP server

Connect Claude Code or Cursor and let your agent launch pages, audit breakpoints, and edit CSS.

Broad web support

Test live sites, localhost, staging, and pages behind login, including sites that normally refuse to be embedded.