How to Test Drive the All-New gThumb 4.0 Alpha on Ubuntu

By ✦ min read

Introduction

gThumb, the beloved open-source image viewer and organizer, has undergone a massive transformation. Its latest alpha release (version 4.0) brings a complete port to GTK4 and libadwaita, resulting in a modern, streamlined interface that is almost unrecognizable from the old GTK3 version. Alongside the visual overhaul, gThumb 4.0 adds support for WEBP and PNG animations, lets you export images in the JXL format, and includes a handy censor filter to pixelate or blur parts of an image. This guide will walk you through installing and testing this alpha build on Ubuntu, so you can experience the future of gThumb firsthand. No special skills required — just a willingness to explore cutting-edge software.

What You Need

• Ubuntu (or a Debian‐based distribution) – The steps below assume Ubuntu 22.04 / 24.04 or later. Other distros can adapt using their package manager.
• Terminal access – You’ll need sudo privileges to add a PPA or install dependencies.
• Internet connection – To download the alpha build and its dependencies.
• Basic familiarity with the command line (optional but helpful).
• An existing gThumb installation is not required – The alpha can coexist with the stable version if you prefer.

Step-by-Step Guide

1. Update your system – Open a terminal and run:
   sudo apt update && sudo apt upgrade
   This ensures your current packages are fresh and reduces the chance of conflicts.
2. Add the gThumb 4.0 alpha PPA – The developers provide an official PPA for testing builds. Add it with:
   sudo add-apt-repository ppa:gnome3-team/gnome3-staging
   (Wait for confirmation.) Then update again: sudo apt update.
3. Install gThumb 4.0 alpha – Install the package with:
   sudo apt install gthumb
   If the PPA is correctly configured, you’ll get the GTK4/libadwaita version. Verify with gthumb --version – it should show “4.0” or later.
4. Launch gThumb – You can start it from the terminal with gthumb or find it in your applications menu. The interface will look dramatically different – flat, with rounded corners, and a clean sidebar. Take a moment to customize the layout via the hamburger menu.
5. Test the new features –
   • WEBP/PNG animations: Open a .webp or .png animated file – gThumb now displays them correctly with playback controls.
   • Export to JXL: Right‑click an image, choose Export, and select “JPEG XL (JXL)” from the format list. This modern codec offers better compression.
   • Censor filter: Open any image, click the edit icon (or press Ctrl+E), then choose Filters → Censor. Select a region and apply pixelation or blur – perfect for anonymizing parts of a screenshot.
6. Provide feedback (optional) – As an alpha, bugs are expected. Report issues on the official GitHub repository. Your input helps shape the final release.

Tips and Conclusion

• Back up your existing gThumb configuration – The alpha may alter your settings. Copy ~/.config/gthumb to a safe location before launching it.
• Experiment with the new UI – The switch to libadwaita brings adaptive elements. Resize the window to see how the toolbar collapses gracefully.
• Keep an eye on performance – The GTK4 port is still being optimized. If you notice lags, try disabling hardware acceleration in preferences.
• Stay up to date – The PPA receives regular updates. Run sudo apt update && sudo apt upgrade periodically to get the latest fixes.
• Check for stable release – Once gThumb 4.0 reaches stable, you can remove the PPA and install the official version from the Ubuntu repos or Flathub.

This alpha is not just a facelift – it’s a leap forward for an already powerful image tool. By following these steps, you’re among the first to explore the modernized interface and new features. Enjoy the ride, and don’t hesitate to share your findings with the community!