About Witek Bobrowski
building software
I'm a Software Engineer building iOS apps and working on open-source projects. Currently pouring most of my free time into ksefuj.to — a free, open-source KSeF invoice validator for Polish businesses. No limits, no paid tiers, no data leaving your browser.
Your support helps me keep shipping open-source tools and stay caffeinated while doing it ☕
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Hey! Thanks for stopping by 👋 I'm currently heads-down on ksefuj.to — a free, open-source invoice validator for Poland's new mandatory e-invoicing system (KSeF). The deadline is April 1, 2026 and small businesses need tools that don't come with a paywall. If you grabbed a coffee for me — thank you, it genuinely means a lot. More updates coming soon.
First post — what I'm working on
Mar 25, 2026
144 views