Live CSS editing

Change CSS once and see it land on every device at the same time.

The editor

Live CSS editing lets you tweak a page's styles right inside Responsive Tester, without leaving the app or switching windows. Open the editor with the edit toggle in the toolbar, a Pro control that arms the editor and gets ready for your first selection.

The editor works the way the browser DevTools inspector does. Pick an element in any viewport, and its matching rules appear in the editor panel. From there you can change existing declarations, adjust a value like padding or font-size, and see the result immediately. If you already know DevTools, there is nothing new to learn: the same pick-an-element, edit-its-rules workflow applies here.

Editing across breakpoints

The reason to edit here rather than in a single browser tab is reach. A change applies instantly in every open viewport at once, so one edit updates the phone, the tablet, and the desktop layout together.

Media queries are included in that reach. When you change a rule that a media query overrides at a given width, each viewport reflects the outcome for its own size, so you see how a single edit reads at every breakpoint at the same time. Instead of resizing one window and re-checking each width by hand, you get the full picture in one glance and can tell right away whether a change holds up across the range.

Change tracking and CSS export

The editor tracks every change you make during a session. As you edit, it keeps a record of what moved from its original value, so you never have to remember which declarations you touched.

When you are happy with the result, export those tracked changes as paste-ready CSS. The export gives you the edited rules as clean CSS you can drop straight into your codebase, which turns a round of visual tweaking into concrete code without retyping anything by hand.

Undo and redo

While the editor is open, standard history shortcuts are available. Press Cmd/Ctrl + Z to undo the last change, and Cmd/Ctrl + Shift + Z to redo it. This makes it safe to experiment: try a value, step back if it is wrong, and step forward again if you change your mind. Undo and redo replay across every viewport, so stepping back rolls the change out of all devices at once, exactly the way applying it did.

Saved CSS edits

Stylesheet-rule edits and rules added in the editor are saved locally in your browser. When Responsive Tester opens another page on the same origin or reloads a viewport, it restores saved changes where the original rule can still be found. A toast confirms how many saved edits were restored. Missing rules stay saved for pages where they are available.

Restoration is available during the trial and with Pro. If your trial has ended, the next activation leaves saved CSS unapplied until you upgrade. An active session is not interrupted. Inline styles and class changes remain session-only.

Discarding a restored change also removes that saved change. Live edits never update your repository files or save to a server, so copy changes into your source code when you want to ship them.