What image formats can I compress?

FileSlim supports JPG/JPEG, PNG, WebP, and AVIF. Each format uses optimized compression algorithms for the best size reduction.

Will image quality be affected?

At default settings, compression is nearly imperceptible. You can adjust the quality slider to find the perfect balance between file size and visual quality.

Can I compress images in bulk?

Yes! Drop multiple images at once. FileSlim processes them all in parallel using Web Workers for maximum speed.

Are my images uploaded anywhere?

No. All image compression happens locally in your browser. Your photos never leave your device — complete privacy guaranteed.

How much smaller will my images be?

Typical compression reduces images 60-85% smaller. A 5MB photo usually compresses to 500KB-1MB without visible quality loss.

Last Updated: August 4, 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

Most photos compress 60-85% smaller without visible quality loss. A 5MB JPEG typically compresses to 500KB-1MB. PNGs with transparency are optimized losslessly. WebP images get additional savings through modern encoding.

— How much can I compress my images?

70-85%

Avg. Reduction

JPG, PNG, WebP

Formats

100% Local

Privacy

Supported Formats

JPG / JPEG

Best for photos. Lossy compression reduces file size 70-90% with minimal visible quality loss.

PNG

Best for graphics with transparency. Lossless optimization removes metadata and optimizes encoding.

WebP

Modern format with superior compression. 25-35% smaller than JPEG at equivalent quality.

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