gThumb 4.0 Alpha: A Modern Makeover with New Features

gThumb, the longtime open-source image viewer and organizer for Linux, has received a major overhaul. The latest alpha release of version 4.0 is rewritten in Vala and ported to GTK4 and libadwaita, resulting in a UI that looks dramatically different from its predecessor. This update not only brings a fresh, modern interface but also introduces several new capabilities, including support for WEBP and PNG animations, export to JXL format, and a censor filter for pixelation or blurring. Below, we answer key questions about this transformative release.

1. What is gThumb and why is the 4.0 alpha such a big deal?

gThumb is a popular open-source image viewer and organiser for GNOME-based Linux desktops. The 4.0 alpha is a landmark release because the entire application has been rewritten in the Vala programming language and ported from GTK3 to GTK4 and libadwaita. This is not a simple facelift—it’s a ground-up rebuild that modernises the codebase, making the app faster, more maintainable, and visually aligned with contemporary GNOME design guidelines. The UI is so different that many longtime users may barely recognise it. While still in alpha, this version demonstrates the direction gThumb is heading: a sleek, fluid image tool that feels right at home on GNOME 40 and later.

2. What new features does gThumb 4.0 alpha introduce?

Alongside the visual overhaul, gThumb 4.0 alpha packs several functional additions:

• WEBP and PNG animations: The app can now handle animated WEBP and PNG files, expanding its use for modern web graphics and stickers.
• JXL export: Users can export images in the JPEG XL (JXL) format, a next-generation image codec offering better compression and quality.
• Censor filter: A new editing tool allows you to pixelate or blur parts of an image, useful for redacting sensitive content or creating artistic effects.

These additions make gThumb more versatile for both casual browsing and light editing tasks.

3. How does the visual revamp differ from the old interface?

The most obvious change is the adoption of GTK4 and libadwaita, which bring a flat, modern look with larger controls, smoother animations, and better integration with the GNOME desktop. The old GTK3 version featured a more traditional toolbar-and-thumbnail layout; the new interface strips away clutter, uses a sidebar for navigation, and adopts the adaptive, rounded design language seen in apps like Files and Settings. Menus and dialogs have been streamlined, and the overall feel is more consistent with the GNOME 40+ experience. It’s not just about aesthetics—the port also improves performance and touch support.

4. What new file format support does the update include?

gThumb 4.0 alpha adds support for two important image formats: animated WEBP and animated PNG (APNG). This means you can view and manage short animations directly in gThumb, which previously only worked with static frames. Additionally, the app now lets you export images in the JPEG XL (JXL) format, a royalty-free codec that aims to replace JPEG with better compression and higher quality. JXL is particularly useful for photographers and web developers who need efficient storage and fast loading.

5. What is the censor filter and how does it work?

The censor filter is a new editing tool in gThumb 4.0 that allows you to obscure parts of an image by applying either pixelation or blurring. You can select a rectangular region (or freehand, depending on future updates) and then choose the desired effect strength. This is handy for redacting personal information in screenshots, blurring faces in photos, or creating mosaic effects. The implementation is straightforward: the filter modifies the selected area in real time, and you can undo or adjust it. It’s a practical addition for anyone who needs quick privacy-protection edits without launching a full image editor.

6. Why is the GTK4/libadwaita port significant for gThumb?

Porting to GTK4 and libadwaita is significant because it future-proofs gThumb. GTK4 offers improved rendering, better touchscreen support, and a cleaner API, while libadwaita provides a consistent design language aligned with GNOME’s visual identity. This means gThumb will look and behave more like other modern GNOME applications, offering a cohesive user experience. The rewrite in Vala also makes the code easier to maintain and extend. For users, the result is a faster, more responsive app that feels native on current Linux desktops.

7. Should I use the gThumb 4.0 alpha for daily work?

The 4.0 alpha is labelled as an early test release, so it may contain bugs, unfinished features, or memory leaks. While many core functions (viewing, browsing, basic editing) work well, you might encounter occasional crashes or performance hiccups. If you rely on gThumb for production or need absolute stability, it’s safer to stick with the stable GTK3 version until a beta or release candidate appears. However, if you’re curious about the new design and willing to provide feedback, the alpha is worth trying in a non-critical environment.

8. When can we expect a stable gThumb 4.0 release?

No official timeline has been announced for a stable release. Given that the current version is still in alpha, it may take several months to reach beta, followed by release candidates. The developers are likely focused on squashing bugs, completing the UI polish, and adding any missing features. Users interested in tracking progress can follow the gThumb GitLab repository for updates. In the meantime, the alpha build is available for testing on Linux distributions that support flatpak or source compilation.