Lossless compression exists. PNG uses it. WebP has a lossless mode too. Zero pixels changed, but the file gets smaller — just like ZIP but for images. Lossy compression at 85%+ is visually identical to the original for photos. The "loss" is real but invisible.
For screenshots and text, yes — JPG artifacts ruin sharp edges. For photos, no — a 4MB PNG photo and a 300KB JPG photo look identical at normal viewing sizes. You're paying 10x the file size for quality you can't see.
Modern browser-based tools handle this just as well. Our compressor uses the same Canvas API that browsers use to render every image you see online — the quality is identical to what you'd get from desktop software.
WebP is great for the web but still can't be opened by many desktop apps. Convert your web images to WebP but keep PNG masters for editing and archiving.
The JPEG committee itself was surprised by this in 2022 — their newer encoders produce files 30% smaller than older ones with the same quality. The relationship between size and quality isn't linear, and smarter compression algorithms are beating this myth every year.