Your first comparison

Three moves. Give it two things, press Enter, read the result. The rest of this page is a tour of what comes back.

Copying one snippet, pasting it into the before slot, copying a second, pasting it into after, and the detection bar resolving — **Copy, paste, copy, paste.** The clipboard fills the empty side first, so two pastes fill both slots.

1. Give it two things#

Any of these routes fills a slot, and nothing downstream cares which one you used.

Route	How
Drag and drop	Drop a file, folder or image onto the BEFORE or AFTER zone
File picker	`⌘O` — opens twice, BEFORE first, then AFTER
Folder picker	`⌘⇧O` — same, for directories
Clipboard	`⌘V` when nothing is focused, or `⌘⇧V` at any time. The empty side fills first
Neither	Press Load sample comparison on the compare screen to run a real pair through the real engine

Each filled zone shows the file's name, its size, the kind TwinScope decided it is, and the first few lines of it. If you got the sides the wrong way round, ⌘⇧S swaps them. Giving it two inputs covers every route in detail.

2. Press `⏎`#

With both slots filled, the detection bar names what will run — Detected: json → Structural JSON diff — and the Compare button lights up. ⏎ does the same thing, as long as you are not typing in a text field.

The compare screen with two inputs loaded and the detection bar naming the engine that will run — **The bar commits before you do.** It names the engine, and says so when the choice is surprising.

If you would rather choose the engine yourself, the dropdown at the end of the bar overrides detection — see Type detection. A text pair over 10 MB asks for confirmation first, because a multi-megabyte diff takes a few seconds and a spinner that long looks like a hang.

3. Read the result#

The workspace opens with the same shape for every engine.

Where	What it tells you
Toolbar	The engine that ran, the controls that engine owns, the search box, Export, and ← New comparison
Summary strip	`N changes`, then ＋ added － removed ～ modified, then whatever counts this engine adds — lines, nodes, regions, identical files
The view itself	The diff, tree or image comparison, filling the rest of the window
Status bar	Which engine ran, how the files were decoded, and how long the comparison took

Counts come first on purpose: the question is almost always how much changed before it is what changed.

Step through the changes#

The ‹ 3 / 17 › stepper in the summary strip and the ⌥↑ / ⌥↓ keys share one index with the view, so the number, the keys and the scroll position can never disagree. See Change navigation.

Take it with you#

Export offers a self-contained HTML report, Markdown for a pull request, and a unified patch copied straight to the clipboard. ⌘⇧E repeats whichever format you used last. See Export.

Then read about your engine#

If you compared	Read
Two files of code, or any text	Text and code
Two JSON documents	JSON
Two directories	Folders
Two screenshots or exported assets	Images
Two executables, archives or opaque blobs	Binary files