Formats

Nine containers, one engine.

Every format stores metadata somewhere different, so each one gets its own parser. What they share is the outcome: metadata gone, pixels untouched.

01JPG / JPEGJPEG stores metadata in application marker segments that sit before the compressed image data. EXIF and XMP live in APP1, the ICC colour profile in APP2, C2PA credentials in APP11, and IPTC inside a Photoshop resource block in APP13. Free-text comments go in a COM segment.
02PNGPNG is a chain of length-prefixed, CRC-checked chunks. Text metadata lives in tEXt, iTXt and zTXt chunks, EXIF in eXIf, the ICC profile in iCCP, timestamps in tIME, and C2PA credentials in a caBX chunk.
03WebPWebP is a RIFF container. Metadata sits in dedicated EXIF and XMP chunks, with the colour profile in ICCP. An extended-format header, VP8X, records which of those chunks are present.
04HEIC / HEIFHEIC uses the ISO Base Media container. Metadata is stored as separate items, with an iinf box naming each item and an iloc box recording exactly where its bytes sit in the file.
05AVIFAVIF shares HEIC's ISO Base Media container, so metadata is stored the same way: as items described by iinf and located by iloc, plus optional top-level uuid boxes for XMP.
06GIFGIF has no EXIF. What it does have are Comment extension blocks and Application extension blocks, where editing tools leave their name and occasionally more.
07TIFFIn TIFF the metadata is the directory structure itself. An image file directory lists every tag, mixing structural entries such as strip offsets with personal ones such as Artist, Software, GPS and XMP.
08MP4videoMP4 keeps metadata in udta and meta boxes inside moov, alongside creation and modification timestamps in the movie, track and media headers. Phones add a QuickTime location atom holding GPS coordinates.
09MOVvideoMOV is Apple's QuickTime container and uses the same box structure as MP4. iPhones write a com.apple.quicktime.location.ISO6709 atom with your coordinates, plus device make, model and software version.