It does let you get an overview of what files have changed, but the diffing algorithm is very poor. If a block of code changes from multi-line to single line, it throws off the diff for the rest of the file. See what algorithm VS Code uses, and use that; they have excellent blog posts on diffing. I ended up exporting the themes and comparing in VS Code using the "Compare Folders" extension. I also cannot find a way to undo individual changes to files. If I accidentally merge a change to the wrong side, or merge the wrong change, I have to discard all changes and start again.

Excellent app that will save you loads of time, and its FREE so win win. Very easy to install and use A++++++

Truly such a helpful and amazing tool! Makes theme updates a breeze and works perfectly. Kudos to the developers for releasing such an awesome tool for free.

Absolutely fantastic tool. Had been fiddling with various plugins and had been fiddling around with layout and css, meaning I broke the layout when I uninstalled them. After a couple of hours looking for the changes, I downloaded this tool, and found the culprit instantly!

Game changer! This tool saves me so much time when upgrading themes. Shopify theme upgrades are a nightmare and this tool makes it so much easier and ensures I don't miss anything. Its very basic, but hey, its free... so no complaints. I particularly like the new feature that can create any additional missing codes files not contained in the original theme by just copying left to right. Freak'in awesome app thank you!!

It's exactly what I've been looking for to track down the changes that were made in the theme code. This should be included as a standard feature as part of Shopify, IMHO. Thank you for providing this useful tool to us!

This is a mind-bogglingly awesome tool for anyone who customizes their themes. The fact that Shopify codes their themes so that customizations break automatic upgrading is idiotic. They should use a parent/child system like WordPress. This app functions like any other diff tool, but it's built right into your Shopify admin like it was coded there by default (and should be). No need to download theme files and find differences, this tool does it all right in the Shopify admin, and will even open files in the Shopify online code editor if need be. Cannot thank the developers enough for this tool. Upgrading my theme was a major pain in the neck because of some slight theme edits. This tool has made that process immensely easier. Please add a tip jar to the app!

Incredibly simple and easy to use. Clearly shows all code, what's changed, how's it changed, and where it's changed at. The perfect companion for checking your theme, especially if you have custom code and are doing a theme upgrade. Huge thanks to the developers!

I am so excited to find this app, and it works well. Comparing build versions of my theme is fast and easy, it shows the results in a clear and easy-to-use way. My deployments will be easy and safe from now on. Awesome and thanks to the developers!!

This app is essential for teams with multiple people working on a site, making changes in the theme customizer while we have developers working on code. It should really be OOB Shopify functionality.