How to fix "Not a PNG file: incorrect file signature" in Photos, Preview, browsers
Not a PNG file: incorrect file signature
What this error means
The first 8 bytes, which identify a PNG, are damaged — the rest of the image is often fine.
Why it happens
- Storage errors at the start of the file
- A program that wrote a header for another format
- Wrong extension (the file is really a JPEG or WebP)
How to fix it
- Run the free check here — if it is another format, we tell you which
- If the signature is damaged, our repair restores it
About PNG image files
A PNG is a signature followed by chunks, each with its own checksum (CRC). Strict viewers refuse the whole image if one checksum is wrong, and a cut-off PNG loses only the bottom rows.