When I first came across Wikimedia Commons as part of my Outreachy project, I saw it as just a place for freely usable media but behind the scenes, Commons is a complex, community-driven platform where contributors work together to maintain, organize, and improve millions of media files.
One of the ways this is done is by adding categories to files, labels that help users find related media. For example, a photo of a bird might be categorized under “Birds,” “Animals of India,” and “Taken in 2022.” But imagine trying to do this for hundreds of files one-by-one. That’s where a tool like Cat-a-lot comes in!
🐈 What Is Cat-a-lot?
Cat-a-lot is a JavaScript gadget, a tool users can enable on their Wikimedia Commons account to help them quickly categorize multiple files at once.
Instead of editing each file manually, you can:
- Select multiple files from a category or search page
- Choose a category to add, remove, or move them to
- Apply the changes with a few clicks
It’s a time-saving tool that helps both experienced contributors and newcomers keep Commons well-organized. That’s why it was given the Coolest Tool Award 2024 for the editor category
While Cat-a-lot was originally built for Wikimedia Commons, it can also be used on other Wikimedia wikis (like Wikipedia or Wikisource) through some manual setup and workarounds. Part of my current work involves making this process more seamless and user-friendly, so contributors across different Wikimedia projects can benefit from it more easily.
🧩 Who Uses It, and Why?
Cat-a-lot is especially helpful for:
- Wikimedia Commons editors who do a lot of maintenance work
- Photographers or institutions uploading large media batches
- WikiProjects working to clean up or standardize categories
- Everyday users who want to contribute by organizing files they come across
Even if you’re not a power user, Cat-a-lot can be a great way to make small but valuable contributions. For example, if you notice a group of uncategorized images while browsing Commons, you can quickly add them to the right category using Cat-a-lot. It makes participating in Commons more accessible and efficient, even for casual contributors.
💻 My Work: Improving the Cat-a-lot Gadget
My Outreachy project focuses on maintaining and enhancing the Cat-a-lot gadget. While Cat-a-lot is already a powerful tool, it was built many years ago using jQuery, and parts of its codebase are outdated. My goal is to make it more reliable, user-friendly, and future-proof for a wider range of contributors.
Here are some key improvements I’ve been working on:
- Supporting large-scale edits, so power users can categorize hundreds of files more efficiently
- Adding support for the “Data” namespace, allowing Cat-a-lot to categorize JSON-formatted data pages, not just image files
- Fixing bugs in the settings and UI, improving the overall user experience
Beyond coding, I’ve also been focused on writing clear developer documentation and creating automation scripts that help new contributors test Cat-a-lot in a safe development environment called Beta Commons.
😵 What Was Confusing at First?
When I first applied, the idea of a “gadget” on Wikimedia Commons was unfamiliar. I initially assumed it meant a browser extension or app, but I later learned that gadgets are actually JavaScript tools you can enable through your wiki user settings, and they run directly within wiki pages.
Another concept I had to get used to was the MediaWiki API, a powerful system that allows gadgets like Cat-a-lot to interact with wiki pages programmatically, such as making category edits without needing to reload the page.
However, the hardest part by far was understanding the legacy codebase of Cat-a-lot. The gadget has been around for many years and has been modified by multiple contributors, each with their own coding style and logic. This made it challenging to trace how the different files and components interacted with one another.
Another difficulty was working on other wikis beyond Commons. Although Cat-a-lot can technically run on other Wikimedia wikis, improving its cross-wiki functionality—like ensuring user settings work consistently—required a lot of trial, error, and debugging, since different wikis can behave in subtly different ways.
While these challenges were frustrating at times, they ultimately helped me build a stronger understanding of how real-world systems and software evolve over time, with all their quirks, legacy decisions, and collaborative complexity. It’s been an invaluable learning experience.
📖 What I’ve Learned
Over the past month, I’ve learned a lot about:
- How Wikimedia gadgets are built and maintained
- The structure of MediaWiki and how Commons handles categories and pages
- Writing code that supports localization (i18n), so the tool works in many languages
- Balancing user experience with performance, especially important on slower internet or mobile
- Debugging and improving legacy code, something not always covered in tutorials.
- Testing on different wikis and environments
🌍 Why This Project Matters
Commons is a massive, collaborative project used globally. Tools like Cat-a-lot empower volunteers to manage content more efficiently. Even small improvements can have a big impact because so many people rely on them.
As someone new to the Wikimedia ecosystem, it’s exciting to contribute to something that feels both technical and meaningful. I get to write code, work with mentors, and make a real-world impact on how knowledge is organized and shared.
🌱 Thinking of Applying to This Community?
If you’re thinking about contributing to Wikimedia, I want to share something honestly: I was intimidated at first, too. Open source projects always seemed too vast and overwhelming, there were large codebases, experienced contributors, and unfamiliar tools everywhere. I worried that I wouldn’t know where to start or that I’d mess something up.
But Outreachy gave me a starting point, and that made all the difference. It helped me ease into open source with mentorship, structure, and encouragement. Once I began contributing to Wikimedia, I discovered that the community is incredibly welcoming, collaborative, and supportive. People were always ready to answer my questions, review my work, and help me grow.
Working on a real-world project like Cat-a-lot not only improved my understanding of JavaScript and MediaWiki, but also taught me how to navigate legacy code, collaborate in a large codebase, and think about building tools for a global audience. I’ve become more confident in my skills, not just as a developer, but as someone who can contribute meaningfully to open source.
If you’re considering applying to Wikimedia or any open source project:
- Don’t be intimidated by the scale, it’s absolutely okay (and smart!) to start small.
- The Wikimedia community is friendly, inclusive, and loves open collaboration.
- Tools like Cat-a-lot are great entry points to learn about JavaScript, MediaWiki architecture, and how contributors work together to improve free knowledge.
You don’t need to know everything to start. If you’re curious, open to learning, and willing to ask questions, you’ll find your place here, just like I did.
Thanks for reading! If you’re interested in trying out Cat-a-lot or contributing to Wikimedia Commons tools, feel free to reach out to me through my LinkedIn DMs or directly onto my wikimedia commons talk page or explore the documentation.
Until next time,
Adiba 😊
