Glossary
The vocabulary, defined.
24 terms, each on its own page, each grounded in what the format specifications actually say rather than in a general summary.
Metadata standards
The specifications that define what a block of metadata contains and how it is written.
- EXIFEXIF is the metadata standard cameras use to record how, when and where a photo was taken, stored inside the image file itself.
- IPTCIPTC is a metadata standard for editorial information — caption, creator, credit, copyright and keywords — rather than camera settings.
- XMPXMP is an extensible, XML-based metadata format that can carry arbitrary fields, embedded in a file or kept alongside it as a sidecar.
- C2PAC2PA is a provenance standard that attaches a signed, tamper-evident manifest to a file, describing its origin and edit history.
- ProvenanceProvenance is the record of where an image came from and what has been done to it since.
Fields and tags
Individual pieces of information inside a file, and what each one gives away.
- GeotagA geotag is the geographic location recorded inside a photo at the moment it was taken.
- GPS IFDThe GPS IFD is the sub-directory of an EXIF block that holds location data, kept separate from the camera and exposure fields.
- Maker noteThe maker note is a proprietary, largely undocumented section of an EXIF block in which a camera manufacturer records whatever it likes.
- Orientation tagThe orientation tag is the EXIF field telling a viewer which way up an image should be displayed.
- ICC profileAn ICC profile is a colour description embedded in an image so that viewers reproduce its colours consistently.
- Embedded thumbnailAn embedded thumbnail is a small copy of an image stored inside its own metadata block, for fast previewing.
- Digital source typeDigital source type is an IPTC metadata field that declares how an image was created, from a camera capture to fully AI-generated.
File structure
How image and video containers are physically laid out, and where metadata sits within them.
- IFDAn Image File Directory is the table structure EXIF uses to store tags, inherited from the TIFF specification.
- APP marker segmentAn APP marker segment is a labelled block in a JPEG file where applications store metadata, ahead of the compressed image data.
- PNG text chunkA PNG text chunk is a named section of a PNG file holding arbitrary text metadata, optionally compressed.
- RIFF chunkA RIFF chunk is a labelled, length-prefixed block in the container format WebP is built on.
- ISO BMFF boxA box, sometimes called an atom, is the nested container unit that HEIC, MP4 and MOV files are built from.
- ChunkA chunk is a self-describing section of a file, carrying its own type label and length.
- Container formatA container format is the file structure that wraps compressed image or video data together with the metadata describing it.
- JUMBFJUMBF is a generic box format for embedding structured data in a file, and the wrapper every C2PA manifest is stored in.
Handling
What happens to a file when it is cleaned, converted or re-saved.
- LosslessLossless means the image data comes out bit-for-bit identical to what went in.
- Re-encodingRe-encoding is decoding an image and compressing it again, which discards detail on every pass through a lossy format.
- Sidecar fileA sidecar is a companion file holding metadata for an image that is left otherwise untouched.
- Invisible watermarkAn invisible watermark is information encoded into the pixels of an image rather than into its metadata.
Questions
Definitions say what a thing is. For what to actually do about it, the answers take one question at a time.
Do photos sent in direct messages keep their EXIF data?Does screenshotting a photo remove its metadata?Do screenshots contain GPS location data?Can image metadata be faked or edited?Do all photos have metadata?Does removing metadata reduce image quality?Why does my photo show no EXIF data at all?How accurate is the GPS location in a photo?