Compare Two Images or Videos Side by Side, Online

If you need to compare two images side by side online — or two videos, or even folders full of pairs — TwinLens does it instantly in your browser. No upload, no account, no plugin. Drag two files in, pick a view, and slide.

This guide walks through the three view modes with live demos you can interact with, then shows how to embed any comparison on your own site in one iframe.

Three ways to compare

Different jobs call for different views. TwinLens ships all three, switchable with a single keystroke (1, 2, 3) or a tap on the toolbar.

1. Side-by-side (split view)

The classic layout — both images, full size, sitting next to each other. Best when you want to see the entire frame of each image at once. Especially useful for ML model comparisons where you need to spot artifacts across the whole frame, or for grading multiple variants at the same time.

TwinLens supports up to 4 images or videos in side-by-side mode, in horizontal, vertical, or grid layouts.

Live 4-up image comparison. Open in new tab →

2. Slider view

The before/after slider — drag a handle across the image to reveal one side or the other. This is the most intuitive way to compare retouches, AI upscales, denoising results, or generative image edits, because the eye instantly notices the difference at the slider boundary.

Live image slider — drag the handle across. Open in new tab →

3. Peek view

Click and hold to swap the visible image; release to swap back. It's the fastest way to A/B between two near-identical frames, because your eyes stay locked on the same point and the change happens in place. Photographers use it for retouches, ML researchers use it for catching subtle model drift.

Click and hold inside the frame to peek between the two images. Open in new tab →

It works for videos too

Every view mode above also supports video. Drop two video files in (or up to four) and TwinLens runs them in synced playback — one scrubber controls all of them, with automatic drift correction so the timelines stay locked. You can play up to 4× speed, jump frame-by-frame, or scrub the slider mid-playback.

It's the only free in-browser tool that does this — most online image comparers don't handle video at all, and the ones that do require uploads.

Live video slider — press play and drag. Open in new tab →

Embed any comparison on your site

Every comparison above is loaded with a single <iframe>. Once you've created a share link in TwinLens (click the Share button, choose Indefinite, copy the URL), append &embed=1 and wrap it in an iframe. That's the whole setup.

A few useful flags you can append to the URL:

• embed=1 — hides the toolbar so the comparison fills the iframe cleanly.
• zoom=false — disables the scroll-to-zoom interaction.
• pan=false — disables drag-to-pan, useful when the comparison is meant to be a fixed framing.
• view=slider, view=split, view=peek — open the embed in a specific view mode.

For a deeper walkthrough of the embed flow with copy-paste snippets, see our dedicated guide: How to Add Image & Video Comparisons to Your Website.

What else is in the box

TwinLens isn't just the three views. A few things most online image comparers leave out:

• Folder comparison — drop two folders, and TwinLens auto-matches files by name and arrow-keys you through every pair. Free, even though most paid tools don't do it.
• Up to 4 images or 4 videos at once — for model checkpoint A/B/C/D comparisons or color-grade stacks.
• 1:1 pixel zoom with synced pan, so any zoom level keeps both sides aligned.
• Snapshot export as PNG with editable labels for client deliverables.
• Nothing uploaded for local comparisons — files stay in your browser unless you explicitly click Share.
• Keyboard-driven — every action has a one-key shortcut. 1/2/3 for views, F to fit, A for actual size, S to swap, E to export.

Who uses TwinLens

The same tool serves a few very different audiences — the read on the data is the same, but the workflows differ. We've written guides for the most common ones: