A photo knows where it was taken.
A picture from a phone carries the phone, the second it was taken, the coordinates, sometimes your name, and a record of every edit. Here is each block, what it reveals, and what FileSanity does with it.
EXIF
Written by the camera or phone at the moment of capture. The block most people have heard of, and the largest.
- Make, Model, LensModel
- The exact phone or camera and lens. Combined with a serial number, it ties every photo you have ever posted to one device.
- DateTimeOriginal, OffsetTime
- The second the shutter fired, and the time zone, so where you were and when.
- GPSLatitude, GPSLongitude, GPSAltitude
- Where the picture was taken, to a few metres. A listing photo carries the street; a photo of a child carries the school.
- BodySerialNumber, LensSerialNumber
- Identifiers for the hardware. Insurance records and warranty claims carry the same numbers.
- Artist, Copyright, OwnerName
- A name, typed once into a camera menu or a phone setting and written into every file since.
- Software
- What last saved the file. Editing software names itself, and so do some phone apps.
- The thumbnail (IFD1)
- A small copy of the picture, sometimes from before it was cropped or redacted.
XMP
Adobe's XML packet, written by editing software and by newer phones. Often duplicates EXIF, and adds the history.
- CreatorTool, CreateDate, ModifyDate
- Which program made and changed the file, and when.
- xmpMM:History
- A list of every edit, with the software and the time of each. It can show a picture was altered, and when.
- dc:creator, dc:rights, photoshop:City, photoshop:Country
- Who made it and where, as text.
- DocumentID, InstanceID
- Unique identifiers that link this file to its earlier versions.
IPTC
The press metadata standard, written by photo software and newsroom systems.
- By-line, Credit, Source
- The photographer and the agency.
- City, Province, Country
- Where, as typed by a person.
- Caption, Keywords
- Free text, sometimes including names of the people pictured.
PNG text chunks
PNG has no EXIF of its own, but screenshots and exports carry text.
- tEXt, zTXt, iTXt
- Key and value pairs: Software, Author, Comment, Source, and an XMP packet in iTXt. A screenshot names the tool that took it; an export names the program and sometimes the file path.
- tIME
- When the image was last changed.
- eXIf
- A full EXIF block, when a converter copied it over from a JPEG.
What is removed.
Every block above: EXIF with its GPS and thumbnail, XMP, IPTC, Photoshop resources and comments in a JPEG; every text chunk, eXIf and tIME in a PNG. The pixels are not decoded or re-saved, so the picture is byte for byte what it was.
Two things stay. The ICC colour profile, because it is how the colours are meant to look, not who took the picture. And when a photo was shot sideways, a single EXIF orientation value is written back, thirty-two bytes, so the clean copy still displays the right way up. The result says when it has done that.
Not read yet: HEIC and RAW files, and the EXIF inside a picture that has been pasted into a Word document.
Clean a photo before it goes anywhere.
Drop it on the home page. The coordinates, the device and the history go; the picture stays.