Juraj Cukan

The Frustration

As a Computer Science student at Comenius University working on various projects, I constantly needed to compress images and PDFs. Every tool I tried had major drawbacks—expensive subscriptions ($10-30/month), poor quality results, privacy concerns from uploading files to unknown servers, or bloated desktop software that was overcomplicated and slow.

The Solo Journey

Rather than settle for subpar tools, I decided to build my own solution. Working entirely alone from my dorm room in Bratislava, I spent months researching compression algorithms, learning advanced JavaScript optimization techniques, and designing a system that could process files entirely in the browser—no server uploads required.

Technical Innovation

• Browser-native processing using Web Workers and WebAssembly for maximum performance
• Multi-algorithm optimization supporting JPEG, PNG, WebP, AVIF, and PDF compression
• Intelligent quality presets that balance size reduction with visual quality
• Batch processing capable of handling 50+ files simultaneously
• Zero-knowledge architecture—files never leave the user's device

Impact

Since launch, FileSlim has processed over 50 million files, helped users save countless gigabytes of storage and bandwidth, and maintained a perfect security record—zero data breaches because files never reach servers. The platform achieves an average 73% file size reduction while maintaining excellent quality.

Mission

I continue to develop FileSlim as a free tool, driven by the belief that everyone deserves access to professional-grade compression without sacrificing privacy or paying expensive subscriptions. I actively maintain the codebase, add new features based on user feedback, and ensure FileSlim remains the most privacy-focused compression tool available.