Remove Metadata From PNG Images
02 A different privacy story than JPEG
Most PNG files aren't camera photos - they're screenshots, graphics, or exports from an editing tool. That
changes the actual risk profile: PNGs rarely carry GPS data, since screenshots don't have a camera GPS to
record in the first place. What they do carry is "ancillary chunks" - tEXt/iTXt
free-text fields (sometimes the name of the software that created the file, or notes left by an editing
tool), an iCCP color profile, and occasionally a genuine eXIf chunk if the PNG
came from a camera or phone rather than a screenshot.
Go deeper: why PNG's own end marker still gets checked for appended data
PNG has a defined end-of-file chunk, IEND, the same way JPEG has an end-of-image marker -
and the same polyglot trick applies: data appended after IEND is invisible to a normal
image viewer but still physically present in the file. Full pixel reconstruction discards it
unconditionally, the same guarantee described on the comparison
page, regardless of what's actually hiding there.
Why PNG is the format steganography actually targets
PNG is lossless - every pixel value you save is exactly the value that gets read back, with no recompression smoothing anything out. That's exactly the property that makes hiding data in the lowest-order bits of pixel values (classic LSB steganography) survive a naive "just strip the metadata" pass completely untouched - the pixels themselves never change, only the metadata around them does. This tool's optional steganography mitigation (clearing the low-order bits of every pixel) exists specifically for this reason, and matters far more for PNG than for JPEG, where recompression already disturbs those bits as a side effect.
Compression presets on a lossless format
Since PNG has no "quality" concept the way JPEG does, the compression presets here control filter and deflate-compression aggressiveness instead - Super Compressed spends more effort finding a smaller encoding of the exact same pixels, not a lower-quality one. Every preset still removes 100% of metadata.