A decade ago already, we built the technology behind Micrio for a specific project: an interactive documentary around Hieronymus Bosch's The Garden of Earthly Delights (NTR, 2016). We needed a way to let anyone, on any device, explore an impossibly detailed painting — seamlessly, without plugins, and without distracting from the story itself.

That technology became the seed for Micrio. What started as a side project quickly grew into a platform used by museums, cultural heritage institutions, educators, healthcare providers, and commercial storytellers. Today, Micrio enables millions of people to explore, learn, and discover online — whether that's a Renaissance masterpiece, a medical visualization, or an interactive corporate story.

Micrio is built and maintained by Q42, the Dutch software company that has always focused on meaningful, human-centered technology. At Q42, side projects sometimes grow into things bigger than expected — and Micrio is a clear example.

Over the years, we've open-sourced certain parts of the ecosystem already: the Micrio CLI and GUI uploader tools are available on GitHub already. But today marks a bigger shift:

👉 The Micrio Client — the core viewer that powers every Micrio experience — is now open source.

https://github.com/Q42/Micrio.Client

Why open source now?

Several factors came together:

• Openness is increasingly required. Many governments and regulated industries demand open-source components for their digital platforms. A proprietary Micrio viewer would simply disqualify us in those cases.
• Security through transparency. By making the client open, anyone can verify how it works. This strengthens trust, both for individual developers and for organizations with strict compliance needs.
• Empowering developers. Micrio has always been about creative use cases. Having access to the client code means developers can dig deeper, learn from the techniques inside, or adapt it to their specific needs.
• Contributing back. Micrio wouldn't exist without the open web and open standards like IIIF. Sharing our client is a way of giving back to the same community that made Micrio possible.
• Future-proofing. Open-source software is less vulnerable to lock-in. This ensures that Micrio can remain a tool people can rely on for years to come, no matter how the web evolves.

What changes for you?

Starting with Micrio 5.0, the licensing and usage model is dramatically simpler:

• No more per-domain licensing. You can now embed Micrio freely on any site, without worrying about licensing restrictions.
• Full data model transparency. Our formats are documented in detail at https://doc.micr.io/, enabling anyone to build fully custom Micrio projects.
• IIIF support included. Micrio is a IIIF-compatible viewer. That means you can use it to present existing IIIF sources without even needing a Micrio account.
• Flexible distribution. Grab the client directly (micrio-5.4.3.min.js) or install it via NPM (@micrio/client).

The repo itself

If you want to dive a little deeper, the open-source repo comes with some interesting details:

• The viewer uses WebAssembly-to-WebGL rendering, as described in our earlier WebAssembly blog post. It's what makes Micrio both lightweight and high-performance in the browser. See the AssemblyScript code in the /src/wasm folder!
• Despite being a swiss army knife of abilities, the client library is only ~130KB (bz2 compressed), or 350KB uncompressed. This footprint has been carefully engineered to keep Micrio fast and efficient even on mobile devices.
• Starting from 5.0, we switched to semantic versioning for version numbers (major.minor.patch). Every release is available in the GitHub Releases section.
• We've also started using (or at least trying to use) AI to help make development and maintenance easier. So far it has been helpful mostly in documenting the codebase (it was hardly documented so far-- mea culpa), and it has helped a lot with upgrading from Svelte 4 to Svelte 5, saving us a lot of time/typing. Though not perfect yet, I do think in a while this codebase will become more maintainable by AI.
• There are AI-helper docs that explain the app's architecture in the /ai folder.

The road ahead

At the moment, the Micrio dashboard, image-processing pipelines, and other server-side services such as the scaled IIIF Image API (blogpost) remain proprietary. These are the pieces that handle uploads, tiling, and global hosting.

We don't yet have a fixed timeline for open-sourcing these components, but we're actively exploring where it makes sense.

A new chapter

From a single painting in 2016, to a platform used worldwide, to an open-source viewer available to everyone — this marks an important new step in Micrio's story.

Check out the repo, explore the code, create issues, and feel free to contribute:

👉 https://github.com/Q42/Micrio.Client

I'd love to see what you'll build with it. Get in touch through [email protected] or GitHub to learn more!

Marcel Duin, Micrio Founder