Thumbico 2.0 is out. It is the first new version since 1.5 in November 2015, and it is not an update but a rewrite from scratch, with a new look, a new icon, and, for the first time, all of its source code open for anyone to read.
If you have never used Thumbico, here is the idea. Windows makes a thumbnail or an icon for every file, folder, and drive on your PC, but it shows them only at a few fixed sizes. Thumbico asks Windows for that image at the size you choose and shows you exactly what comes back, pixel for pixel. It is not an icon editor, and it doesn't dig icons out of a program's files or draw a preview of its own: it shows the same image File Explorer draws, for anything Windows can show, from programs and documents to photos, videos, folders, and whole drives.
That makes it handy for a lot of small jobs. Writers use it to get a program's icon at its largest size for an article or a slide. Designers and developers use it to check how an icon looks at every size and how its transparency holds up. And anyone curious can see what a video or photo thumbnail really looks like at 1024 pixels. Reviewers liked the earlier versions for how simple they were, and AddictiveTips wrote that "the simplicity of the application is its greatest strength". That has not changed in 2.0: you still drop a file on the window and see its image.
Why we started over
Fair warning: this part is the developer's side of the story, and it gets a little technical. If you only came for the new features, skip ahead. We won't take it personally.
The original Thumbico was written in C# with Windows Forms, on the .NET Framework that came with Windows. In 2011 that was a sensible choice: there was nothing extra to install and the download was tiny. But Windows Forms did not keep up with Windows. On displays scaled to 150 or 200 percent, now common on laptops, its windows often looked blurry or slightly broken, and it never got a proper dark theme. The .NET Framework itself was frozen in time. It still comes with Windows, but it gets only security fixes.
The new, open source .NET does improve Windows Forms, yet it still struggles with scaled displays and dark mode, and it no longer comes with Windows. An app built on it either asks you to install .NET first or carries its own copy, which turns a small utility into a download of more than 50 MB.
So we rebuilt Thumbico with Flutter, Google's open source toolkit for apps. It draws a sharp interface at any display scale, follows the Windows light and dark themes, and needs nothing else installed. The whole download, installer or portable, is about 12 MB. The idea stayed the same, but almost everything around it is new.
What's new in Thumbico 2.0
The first thing you'll notice is the window: one clean window with a toolbar, the image, and a status bar, in light or dark to match your Windows setting. Drop a file, folder, or drive anywhere on it, from Explorer or any other program, and Thumbico reads it at once. The keyboard shortcuts are the ones you already know from other Windows apps, such as Ctrl+O, Ctrl+S, F5, and F1, and the window opens the next time just as you left it, with the same size and options.
Choosing the image is more direct too. Type any size, square or not, pick one of the sizes Windows itself uses, or step up and down with Ctrl+plus and Ctrl+minus. Ask for the best image, a thumbnail only, or an icon only, and turn Windows' own rendering options on and off. Every change shows at once, so you can see exactly what each option does. On a scaled display, Thumbico shows one image pixel per screen pixel, so what you see is what Windows made rather than a stretched copy. When you want to see the image the way Explorer draws it, you can switch to the display's scale.
Once you have the image you want, save it as PNG, JPEG, BMP, GIF, or, new in 2.0, ICO, with transparency kept in PNG and ICO. Or copy it to the clipboard and paste it straight into another app. For screenshots and presentations, Showcase mode, which replaces the old Naked mode, hides everything but the image and shows it on the transparency grid or a plain background. Press F11 to go in and out.
You can install Thumbico for yourself alone, with no administrator rights, or for everyone on the PC. Or take the portable version, a ZIP file you can extract anywhere, even on a USB drive, which keeps its settings beside it. And the green Easter Island head that has been Thumbico's icon since 2011 is still here, redrawn flat and simple. The version history has the full list of changes.
Free, and now open source
Thumbico is still free, with no account, no ads, and no telemetry. What is new is that it is also open source. Earlier versions were free but closed, while Thumbico 2.0 is released under the MIT License, with all of its code on GitHub. You can see how it works, build it yourself, report a bug, or send a fix.
Thumbico 2.0 is written in Dart, the language behind Flutter. If you are curious about Flutter apps on the Windows desktop, the project's README explains how Thumbico is put together, from the part that talks to the Windows shell to the few lines of C++ that let you drop files on the window.
Get Thumbico 2.0
Thumbico 2.0 runs on 64-bit Windows 10 and Windows 11, and you can download it as an installer or as a portable ZIP. It is not code-signed yet, so Windows SmartScreen may warn you the first few times you run it. If it does, choose More info, then Run anyway.
Aurelitec has been making small, focused Windows apps since 1999, and it feels good to give one of them a fresh start. If you try Thumbico 2.0, we would love to hear what you think. Write to us through our support page, or open an issue on GitHub.
Posted on October 9, 2026