The best before and after image comparison tools in 2026

Comparing two images sounds simple until you try to show someone the difference. A screenshot loses the interaction. A side by side crops too small. What people actually want is a slider they can drag across a before and an after, then a link they can send.

The classic tool for this, imgsli, is currently offline and shows a parked “under construction” page. That has left a lot of photographers, retouchers, modders, and AI upscaler fans looking for something else. Below are the tools worth knowing in 2026, grouped by the job they do, so you can pick the one that fits.

Lightweight “make a before/after and share it” tools

This is the category most people mean when they say “image comparison tool”: upload two images, drag a divider, share the result. No install, no code.

imgi

imgi (this site) is a free tool for turning two images into a shareable before/after. You drop in two images, drag the slider horizontally or vertically, and get a permanent link. A few things set it apart in this group: every comparison has a real iframe embed you can paste into a site, blog, or mod page; you can export a comparison as an animated GIF, MP4, or WebP for places that will not host a live slider, like Reddit, Discord, or Nexus; and you can load up to ten images and switch which pair is shown. There is a private mode for images you do not want public, an offline mode that keeps images in your browser, and no signup is needed to start. A Pro tier ($3.99/mo) removes the watermark, unlocks private uploads and ad free viewer pages, and raises export quality.

Best for: creators who want to show a difference and share it anywhere, especially modders, upscalers, photographers, and designers.

Try it: drag the slider below.

imgdiff.net

imgdiff.net is a clean browser tool with a drag divider, plus zoom, pan, and fullscreen. It works on two images, a “Before” and an “After,” with editable labels, and gives you a public share link. It also has an offline mode. Anonymous uploads are public with no password, and it warns you not to upload sensitive files. Free accounts add a small dashboard and favorites.

Best for: a quick, no frills two image comparison with a share link.

pxcmp.com

pxcmp.com bills itself as a “Pixel-Perfect 4K Image Comparison Tool” aimed at gamers and developers. It supports BMP, PNG, JPEG, and WebP, up to twenty images, 32MB each, with zero re-compression and RAW support. Files are kept for a year, you get permanent share links, and you can import by pasting a URL. One thing to know: you have to request a free access key before you can upload. It runs no ads and no trackers.

Best for: pixel level, high resolution comparisons where lossless quality and image count matter more than instant access.

Heavyweight diff and QA tools

These are built to measure differences, not just show them. Different job, different audience.

Diffchecker

Diffchecker is the big one here. Its image mode offers side by side, highlight, fade, and slider views, supports JPG, PNG, WebP, GIF, HEIC, and PDF, and adds auto alignment, change detection, OCR for text inside images, and EXIF metadata comparison. It also diffs text, Word and PDF documents, Excel, and folders. You can save to the cloud and share a link on the free tier, with PNG export capped at five per month. Paid plans run from $15/user/mo (Pro plus Desktop) up to Legal at $20 and Enterprise at $40.

Best for: QA engineers, lawyers, and document reviewers who need to catch and prove changes.

slow.pics

slow.pics has been running since 2017 and is beloved in the video encoding community. You upload sets of frames and flip between them with clicks or hotkeys, and it hands you thumbnails plus HTML and BBCode links. It handles lossless PNG and is built for judging encoder output frame by frame.

Best for: video encoders comparing frames across settings or codecs.

Developer libraries (do it yourself)

If you are a developer and want a slider inside your own product, you write a little code and host the images yourself. Common options include JuxtaposeJS from Knight Lab, img-comparison-slider (with React, Vue, and Angular wrappers), and TwentyTwenty. These give you full control and zero convenience: there is no hosted share link, you bring your own images and page.

Best for: developers embedding a slider into an app they control.

How to pick

Match the tool to the job:

• You want to show a difference and share it fast: a lightweight tool. imgi if you want an embed or an animated export, or many images; imgdiff.net for a quick two image share; pxcmp.com if lossless 4K quality is the point and you do not mind requesting an access key.
• You need to measure and prove a change (legal, QA, document review): Diffchecker.
• You compare encoder frames: slow.pics.
• You are building your own product: a developer library.

For most people replacing imgsli, the lightweight category is the right one. If you want to try the drag, share, and embed flow right now, it takes about ten seconds.