The best free image slider and online image comparer — for ML engineers comparing model outputs, photographers showing before/after, drone operators reviewing aerial shots, and QA teams spotting visual regressions. Compare two images side by side, two videos in synced playback, or two folders at once — drop the files and see the difference.
Free forever · No ads · Works offline · Nothing uploaded
One tool, four kinds of work. Each flow works the same way: drop files, drag, done.
Compare generative image/video model results or checkpoints — 2, 3, or 4 at a time. Drop a folder of HR/LR pairs and arrow-key through them. Grid-view up to 4 outputs at 1:1 pixel accuracy.
Compare model outputs →Show clients before and after a retouch. Drag the image slider to compare two images side by side online — the fastest way to present a retouch in real time. Check exported files against the original without losing detail. HEIC and TIFF supported natively.
Compare photos →Before/after property shots, seasonal comparisons, renovation documentation. Share a link your clients can open — no account needed on either end.
Compare aerial shots →Synced playback of up to 4 videos at up to 4× speed. Compare renders, encoding passes, color grades, or generative video model outputs. Record the comparison as MP4.
Compare videos →Six things most online image comparison tools don't do — or charge for. TwinLens ships all of them, free.
Drop two folders. TwinLens auto-matches files by name and lets you arrow-key through every pair. Most tools — even paid ones — don't have it.
Up to 4 videos, one scrubber, shared speed control up to 4×, automatic drift correction. Most web comparison tools — even paid ones — don't do video at all.
Grid, horizontal, or vertical layouts — for both images and videos. Useful for model checkpoints, multiple color grades, or A/B/C/D test variants.
Processing happens entirely in your browser or desktop app — even client NDA work stays safe. The optional share link is explicit: you click it, your files go up, and they auto-delete in 2 weeks.
Images fill your whole viewport. Every action has a one-key shortcut. Compare at 1:1 pixel accuracy without fighting the UI.
Export a snapshot of any comparison as a clean PNG. Rename labels under each image to call out exactly what you're comparing. Or send a shareable link — your client opens it in their browser, no account or install needed on either end. Built to prepare and deliver visual reports.
Want the full walkthrough? Read the complete feature tour →
Every view mode, toggle, and export has a one-key shortcut.
| Action | Key | Description |
|---|---|---|
| Split View | 1 | Side-by-side comparison |
| Slider View | 2 | Draggable slider overlay |
| Peek View | 3 | Click-and-hold to reveal |
| Swap | S | Swap left and right images |
| Fit | F | Fit images to window |
| Actual Size | A | Show images at 100% (1:1) |
| Details | D | Toggle image info panel |
| Labels | L | Toggle editable labels |
| Snapshot | E | Export comparison as PNG |
| Reload | R | Clear all and start over |
| Add Image | + | Add another image (up to 4) |
| Play / Pause | Space | Toggle video playback (video mode) |
| Seek Back | ← | Jump back 5 seconds (video mode) |
| Seek Forward | → | Jump forward 5 seconds (video mode) |
TwinLens is built with a simple philosophy: your images and videos are yours. Everything runs locally with zero network activity.
Files stay on your device.
No account, no paywall, no ads.
Full-viewport, keyboard-driven, no clutter.
Desktop app for Mac and Windows.
Free, lightweight, and ready to use in seconds.
Apple Silicon & Intel
Windows 10 & 11 (64-bit) — Coming soon
Found a bug? Have an idea? Just want to say thanks? Let us know.
Problem-focused walkthroughs for the kinds of comparison work people actually do.
Fast, browser-based video comparison for ML engineers, QA teams, and researchers. Drop up to 4 videos, compare frame by frame, and export results — entirely in the browser.
Compare videos online → TutorialCompare large image datasets — like HR/LR pairs — in seconds. Drag two folders in, auto-match by filename, navigate with arrow keys, open a gallery, and inspect per-image metrics.
Compare image folders → TutorialA complete guide to comparing images and videos side by side in your browser. Covers drag-and-drop, slider view, zoom, video playback, labels, snapshot export, and shareable links.
Compare images online → TutorialTurn any TwinLens comparison into a link — or embed it in your site with an iframe. Share with clients, teammates, or readers; links auto-expire in 2 weeks so nothing lingers.
Share and embed →Everything you need to know before getting started.
Yes — completely free, forever. No account required, no payment, no trial. Use it in your browser right now or download the desktop app.
No. All processing runs locally in your browser or desktop app. Your images and videos never leave your device unless you explicitly click Share to generate a link — works for both images and videos.
Images: PNG, JPG, WebP, AVIF, GIF, BMP, SVG, HEIC/HEIF (iPhone photos), and TIFF. Videos: MP4, WebM, and MOV. Works in both the browser tool and the desktop app — no conversion needed on your end.
Yes. TwinLens supports up to 4 images or up to 4 videos simultaneously, arranged in horizontal, vertical, or grid layouts with swap controls between each panel. Videos play in lockstep with a shared seek bar and automatic drift correction.
Click the Share button in the toolbar. Your images are uploaded and a shareable link is generated that preserves your exact view, zoom, position, and labels. Links expire automatically after 2 weeks.
Yes. Drag two folders into TwinLens and it automatically matches files by filename. Navigate between pairs with arrow keys, open a gallery view, and check per-image metrics like resolution and file size — perfect for comparing image datasets or HR/LR pairs online.
Can I embed a TwinLens comparison on my website?
Yes. Generate a share link, then use the URL in an iframe. Real estate sites, product review pages, and blog tutorials use this to show before/after or option-A/option-B without hosting their own comparison widget. Full walkthrough →