Does PNG compression lose quality?

Lossless PNG compression preserves every pixel exactly. FileSlim uses OxiPNG optimization to reduce file size without any quality loss. Lossy mode offers more aggressive compression with minimal visual difference.

Will transparency be preserved?

Yes! PNG transparency (alpha channel) is always preserved during compression. Your transparent backgrounds, logos, and overlays remain intact.

How much can PNGs be compressed?

Lossless compression typically reduces PNGs 10-40%. Lossy compression can achieve 60-80% reduction. Results depend on image content — screenshots compress more than photos.

Should I convert PNG to JPG instead?

Only if you don't need transparency. JPG doesn't support transparent backgrounds. For photos without transparency, JPG is smaller. For logos, icons, and graphics with transparency, keep PNG.

Last Updated: September 12, 2026

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Juraj Cukan

Founder, CEO & Lead Developer

Student, Comenius University - Faculty of Mathematics, Physics and Computer Science

Full-Stack Developer

Compression Algorithm Specialist

50M+ Files Processed

Juraj is a Computer Science student at Comenius University in Bratislava, Slovakia, and the sole creator of FileSlim. Frustrated with inefficient and expensive compression tools, he built FileSlim from the ground up as a free, privacy-first alternative. Working entirely alone, Juraj developed every aspect of the platform—from the compression algorithms to the user interface—ensuring complete browser-based processing that never uploads files to servers. His work has helped users worldwide compress over 50 million files while maintaining complete privacy and achieving 60-90% file size reductions.

Quick Answer

PNG uses DEFLATE compression (lossless). FileSlim's OxiPNG optimizer finds the best filter and compression settings to minimize file size without changing a single pixel. Optional lossy mode reduces color palette for even smaller files.

— How does PNG compression work?

10-40%

Lossless

60-80%

Lossy

Preserved

Transparency

Why Compress PNG Files?

Preserve Transparency

Unlike JPG, PNG supports transparent backgrounds. FileSlim compresses PNGs while keeping full alpha channel transparency intact.

Lossless Quality

Lossless mode preserves every pixel exactly. Perfect for screenshots, diagrams, logos, and UI elements where precision matters.

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Reduce PNG size while preserving transparency — free and private.

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