What metadata is in your photos — and what removing it does not do
I was told to strip EXIF before posting a photo. What is in there, and is that actually enough?
What is actually attached to a photograph
A photograph is pixels plus a surprising quantity of prose about the pixels. Most of it is written automatically, by the camera or by whatever software touched the file afterwards, and none of it is visible when you look at the picture.
| Block | Typical contents | Written by |
|---|---|---|
| EXIF | Date and time, camera make and model, lens, exposure, ISO, orientation, thumbnail | The camera |
| GPS (an EXIF sub-block) | Latitude, longitude, altitude, sometimes bearing and a timestamp | The camera, if location is enabled |
| Maker notes | Vendor-specific data: serial numbers, focus points, internal settings | The camera |
| XMP | Editing history, captions, keywords, ratings, rights statements | Editing software |
| IPTC | Captions, credit, source, contact details, usage terms | Editors and agencies |
| ICC profile | The colour space the pixel values are meant to be interpreted in | The camera or the editor |
Why any of it matters
GPS coordinates are the obvious risk: a photograph taken at home carries the address of the home. But the quieter fields matter too. A camera serial number in the maker notes links every photograph that camera ever took. A timestamp places you somewhere at a particular minute. An XMP editing history can name the software, the operator and the original filename, which sometimes contains a client's name or a project code.
Some platforms strip most of this when you upload. Some do not. Some strip it from the copy they display and keep the original. You cannot tell from the outside, which is why removing it before the file leaves your device is the only version of this you control.
What stripping removes
A metadata cleaner rewrites the file without the marker segments that carry EXIF, GPS, XMP, IPTC and maker notes. The pixels are untouched where the format allows the metadata to be edited in place. FileSlimmer keeps two things deliberately: the ICC colour profile, because dropping it makes colours shift in any viewer that respects colour management, and the effective orientation, because dropping that makes photographs appear rotated.
What stripping does not do
This is the part that gets left out of most advice, and it is more important than the part above. Removing metadata removes text about the image. It does nothing about the image.
- It does not remove what is visible in the frame: faces, house numbers, street signs, number plates, a screen with an email open on it, a reflection in a window, a name badge, a distinctive skyline.
- It does not remove information you can infer from the picture: the season, the weather, the time of day from the shadows, the language on the shopfronts.
- It does not affect copies you have already sent. Metadata travels with the file, so every copy in every inbox still carries what the original carried.
- It does not change what a service recorded when you uploaded: an IP address, an account, an upload time. That data lives on their servers and is nothing to do with the file.
- It does not remove the file's name, which people routinely forget is descriptive, or the folder path if you send an archive.
- It does not make a photograph untraceable to a camera. Sensor pattern noise is a property of the pixels, not of the metadata, and forensic work on it is a real field.
So the honest summary is: strip metadata, and then look at the picture again with the question "what does this frame tell someone who is trying to find out where I was".
Formats behave differently
In a JPEG, the metadata lives in application marker segments that can be dropped without touching the compressed image data, so stripping is lossless and the pixels are bit-identical. PNG stores metadata in ancillary chunks, which can also be removed without re-encoding. Some formats and some edge cases make an in-place rewrite impossible, and then the only way to remove the data is to decode and re-encode the image — which does change the pixels. FileSlimmer says so before it does it, rather than quietly re-compressing your photograph.
A practical routine
- Turn off location tagging in the camera app for anything you expect to publish. Not recording it is better than removing it later.
- Strip metadata as the last step before the file leaves your device, not somewhere in the middle of an editing pipeline that will write new metadata afterwards.
- Rename the file to something that says nothing.
- Look at the frame itself for the things listed above.
- Keep an untouched original somewhere private. Metadata is useful to you even when it is a risk to publish.
Verifying that it worked
Do not take a tool's word for it, including this one. Open the cleaned file in a metadata viewer — most operating systems show a properties panel, and command-line readers exist for every platform — and confirm the fields you cared about are gone. If a field you expected to disappear is still there, that is worth knowing before you publish rather than after.
Tools for this
Sources
- CIPA DC-008 — Exchangeable image file format for digital still cameras (Exif)
- Adobe — XMP Specification
- IPTC — Photo Metadata Standard
- International Color Consortium — ICC.1 profile specification