· 3 min read
Your photos know where you live
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Every photograph carries a second, invisible photograph: a block of descriptive text that cameras and phones generate without asking, and which almost nobody bothers to inspect. The format is called EXIF, and it can reveal far more than the picture itself.
What hides inside
Open an ordinary smartphone photo in a metadata viewer and the inventory can be startling. GPS coordinates, often accurate within a few metres, sit beside the altitude and the compass direction the lens was facing. The capture time appears down to the second. Then come the manufacturer and model of the device, the lens, in some cases the camera body's serial number, and every exposure setting: ISO, aperture, shutter speed, focal length, whether the flash fired. Even the editing application that last touched the file leaves its signature.
Photograph your cat on the balcony, publish the untouched original, and you've disclosed your home address, the hours you tend to spend at home, and the hardware you own. The cat remains oblivious.
The thumbnail problem
A subtler danger lurks underneath. Many image files contain a miniature embedded preview, and certain editors update the primary image after you crop or obscure something without regenerating that preview. People have cropped away a face or a confidential document, shared the result, and distributed, without realising, the uncropped original folded inside the file as a thumbnail.
Where it escapes
The large social platforms discard most metadata during upload, an economy measure intended to conserve storage. The leakage occurs at the periphery. Sending a picture through a messenger as a file or document instead of as a photo preserves everything, and so do email attachments. Cloud storage share links deliver the original file byte for byte. Classified listings and forums often store uploads unaltered, and a personal website or blog will publish whatever it receives, metadata included, if its software never intervenes.
This site intervenes. Before storing any uploaded photo, it discards the metadata wholesale; JPEGs retain their orientation tag and nothing more, so they don't appear sideways. Location data and camera details never survive the upload.
Inspecting a photo
ExifTool reads and writes almost every metadata format in existence:
# everything, grouped by where it's stored
exiftool -a -G1 photo.jpg
# just the location
exiftool -gps:all photo.jpgNo terminal handy? Most desktop image viewers include a "properties" or "information" panel, and on a phone the photo's information screen will display a map whenever coordinates are present.
Removing it
To eliminate the coordinates and preserve every other attribute:
exiftool -gps:all= photo.jpgTo eliminate everything apart from the orientation instruction, which prevents the image from appearing sideways:
exiftool -all= -tagsfromfile @ -orientation photo.jpgExifTool preserves a backup named photo.jpg_original; append -overwrite_original once you trust the process. Supplying a directory instead of a filename cleans every image inside it.
On an iPhone, the share sheet hides an Options button at the top that toggles Location off for that particular share; the permanent switch lives under Settings → Privacy & Security → Location Services → Camera → Never. On Android, Google Photos offers location removal during sharing, and most camera applications expose a "save location" switch among their settings.
When metadata earns its keep
None of this makes metadata villainous. It's how your gallery sorts itself by date, how a map of your travels materialises, and how you rediscover which settings produced that one astonishingly sharp nocturnal exposure. My photomap project depends on it: it extracts GPS and exposure details from photographs and positions them as markers on an interactive map.
The principle I follow is uncomplicated. Preserve everything in your private archive; strip it from the copy you share. Your originals remain valuable to you, and strangers receive nothing beyond the picture.