TwinLens is a free, browser-based image and video comparison tool with a minimalist design that uses your full screen for comparison — no sidebars, no clutter, nothing to install. This guide walks you through every step, from loading your first image or video to sharing a permanent link with a colleague.

Step 1 — Open the tool

Go to twinlens.app/compare

No account, no install, no email required. The tool runs entirely in your browser. Your images never leave your device — everything is processed locally.

The interface is intentionally minimal: two empty image panels fill your entire screen, ready to receive your images.

Tip: Bookmark the URL so you can open TwinLens in one click next time.

Step 2 — Load your images

Drag, drop, or click to load

You have two ways to load images or videos:

Drag and drop: drag an image or video file from Finder or Explorer and drop it onto the left or right panel.
Click to browse: click anywhere on an empty panel to open a file picker.

Supported image formats include JPG, PNG, WebP, AVIF, HEIC, GIF, TIFF, and BMP. For video, TwinLens supports MP4, WebM, and MOV. You can load up to four images (or two videos) and switch between side-by-side, horizontal, and grid layouts.

Tip: You can also paste an image directly from your clipboard with ⌘V (Mac) or Ctrl+V (Windows).

Step 3 — Choose a view mode

Slider, Split, or Peek

Use the mode buttons in the toolbar to switch between views:

Mode	How it works	Best for
Slider	Drag a vertical divider left or right to reveal one image over the other	Before & after retouching, UI revisions
Split	Both images sit side by side with a fixed divider	Color grading, layout comparisons
Peek	Click and hold to see the second image; release to snap back	Spot-checking subtle differences quickly
Diff	Highlights pixel-level differences in red and shows a similarity score	QA, design reviews, version diffing

Keyboard shortcut: press S to toggle between Slider and Split view without touching the toolbar.

Try it yourself: Open this live demo to see four images compared in grid view — zoom, pan, and switch views to explore the differences.

Step 4 — Zoom in and inspect details

Synced zoom & pan

Scroll anywhere in the comparison area to zoom in. Both panels zoom and pan in sync, so you always inspect the same region of both images at the same time.

Drag to pan after zooming in.
Press F to fit both images to the window.
Press 1 to jump to 100% (1:1 pixel view) for maximum detail.
Double-click to reset zoom.

Tip: In Split mode, hold Alt and drag to pan only one panel independently.

Step 4b — Label and annotate

Add labels to your panels

Click the label area beneath each image to type a custom name — for example Before Retouch and After Retouch. Labels appear on the comparison view and are included in exported snapshots.

In Slider mode the labels float at the bottom-left and bottom-right of the panel so they stay visible regardless of slider position.

Step 4c — Compare videos

Side-by-side video comparison

Drop two video files (MP4, WebM, or MOV) onto the panels to enter video mode. TwinLens plays both videos in sync with a shared seek bar, play/pause button, and speed control in the toolbar.

Playback starts automatically when both videos are loaded.
If the videos have different durations, the shorter one loops to stay in sync.
Use the speed selector to slow down to 0.25x or speed up to 2x.
Press Space to play/pause, ←/→ to seek 5 seconds.

Tip: Click the Snapshot button while a video is playing to capture the current frame as a PNG — great for pinpointing a specific moment.

Step 5 — Export or share

Snapshot & Share buttons

Export a snapshot

Click the Snapshot button (camera icon) in the toolbar to download the current comparison view as a PNG. The exported image includes both panels, the divider, and any labels you have set. Press P for a keyboard shortcut.

Generate a shareable link

Click the Share button (link icon) to upload your images and generate a permanent shareable URL. Anyone with the link can view your comparison — they do not need a TwinLens account or install.

Images are stored securely and linked to the share ID only.
The link opens directly in the same view mode you had active.
Copy the URL from the dialog and paste it into Slack, email, or a design review thread.

Privacy note: If you do not use the Share feature, your images are never uploaded. All comparison, zoom, and diff operations happen locally in your browser.

Keyboard shortcuts reference

TwinLens is designed for keyboard-first workflows. Here are the most useful shortcuts:

Key	Action
S	Toggle Slider / Split view
F	Fit to window
1	100% zoom (actual size)
P	Save snapshot to PNG
X	Swap left and right images
?	Show all shortcuts
Space	Play / Pause video
← / →	Seek video ±5 seconds

Common use cases

Photo retouching: load the original RAW export and the edited JPEG to review every adjustment.
UI design reviews: compare the mockup PNG with a browser screenshot to catch spacing and color drift.
Before & after: real estate photos, product shots, landscape photography — drag the slider to create a dramatic reveal.
QA & regression testing: use Diff mode to spot pixel-level regressions between two builds of a rendered UI.
Print prepress: check that the CMYK PDF export matches the RGB screen proof at 100% zoom.
Video editing: compare two renders of the same clip side by side — different color grades, codecs, or export settings — with synced playback.

Ready to compare?

Free, private, and instant. No account or install needed — just open the tool and drop your images or videos in.

Compare Now — No Install Needed →

How to Compare Two Images Online — Step by Step