Compress PNG
Real PNG optimization, not canvas re-saving: OxiPNG runs in your browser and shrinks the encoding while every pixel and the alpha channel stay identical. Originals kept when they are already optimal.
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JPEG, PNG, WebP · verified by file signature · processed one by one within this device's memory budget · nothing is uploaded
Browser encoder; bytes vary slightly between browsers.
Lossless OxiPNG optimization: pixels stay identical, so there is no quality setting. Convert to JPEG or WebP for lossy savings.
The honest PNG pipeline
Drop PNGs and they go straight through OxiPNG at optimization level 2, with the codec named on every result. No decode-recode through canvas when nothing else changes, so metadata-free, pixel-identical output; add a resize and the image is redrawn first, then optimized. Files whose headers reveal absurd decoded sizes are refused before decoding with the memory math shown, and animated PNGs are refused rather than silently reduced to their first frame.
PNG compression FAQ
How can PNG compression be lossless?
PNG stores pixels through filtering plus DEFLATE compression, and encoders differ enormously in how well they choose filters and pack the data. OxiPNG, the optimizer embedded here as WebAssembly, retries those choices exhaustively: the decoded pixels stay bit-for-bit identical while the file shrinks. That is why there is no quality slider in PNG mode; there is nothing lossy to trade away.
Why do most online tools make my PNG bigger?
Because they redraw the image on a browser canvas and re-save it with the browser’s basic PNG encoder, which typically produces looser encoding than whatever produced your file. This tool detects that outcome: if the optimized result is not smaller than your original, you keep the original byte-for-byte and the card tells you, instead of shipping you a worse file.
When should a PNG become a JPEG or WebP instead?
When it is a photograph. PNG is lossless by design, and photographic detail costs enormous bytes to store losslessly: a photo saved as PNG is routinely 5 to 10 times larger than a visually identical JPEG. Keep PNG for screenshots, diagrams, logos and anything needing transparency; switch the output format above to JPEG or WebP for photos, and the transparency handling is explicit either way.
Is transparency preserved?
Fully, in PNG output: lossless optimization cannot touch the alpha channel. If you convert a transparent PNG to JPEG, which has no alpha, the tool detects transparency with a full-resolution scan, flattens onto a matte color you choose, and says so on the result card. Nothing is flattened silently.
More free tools: Image Compressor · Compress JPEG · Image Converter · Image Resizer