Smaller file, identical image — honestly
PNG is a lossless format, but most PNG files are written lazily: quick filters, generic compression settings, metadata nobody needs. OxiPNG re-encodes the same pixels with better filter choices and tighter DEFLATE streams. The result decodes to exactly the same image — this is not "barely visible loss", it is mathematically zero loss.
Screenshots, UI mockups and logos shrink the most — often by half. Photos saved as PNG shrink less; if a photo doesn't need transparency, converting it to JPG or WebP saves far more. And if your file is already optimal, we tell you honestly and keep the original instead of returning a bigger one.
Frequently asked questions
Is it really lossless?
Yes — mathematically. The optimized file decodes to the identical pixels. Only the internal encoding and unnecessary metadata change.
Why did my file barely shrink?
It was probably exported by a tool that already optimizes well. PNG photos also compress poorly by nature — for photos without transparency, JPG or WebP is the right format.
Does it remove transparency or color profiles?
Transparency is always preserved. Non-essential metadata chunks are dropped — that's part of where the savings come from.