Hi, I'm Johannes Filter.

I'm a freelance full-stack developer working with Next.js, React, and Django. I build data-driven applications — from interactive visualizations to ML-powered tools. I also help nonprofits and organizations set up and customize CiviCRM, an open-source constituent relationship management system.

I'm an activist for more transparency in the public sector and part of the German open data / civic tech / freedom of information community. I write about my investigative reporting using German FOIA laws on ifg.jfilter.de (in German).

I hold a master's degree in computer science from the Hasso Plattner Institute with a focus on data visualization, machine learning, and natural-language processing. I regularly contribute to open-source software on GitHub and write about technical topics on my blog. You can find more information about myself in my CV.

Check out my previous work, see what services I offer, and follow me on Mastodon or Bluesky.