Photo files hold more than the picture
Phones and cameras save extra information called EXIF with each photo: capture time, device make and model, lens and exposure settings, and, when location services are on, the GPS coordinates of where it was taken.
Posting an original photo taken at home, such as a marketplace listing or a picture of your child, can reveal where you live through those coordinates. Some services strip this data on upload, but not all of them, and “send original” options in email, cloud storage and messengers usually keep it.
How to check whether a photo has a location
On Windows, right-click the photo and open Properties > Details to see whether there are GPS fields. In Preview on a Mac, Tools > Show Inspector shows GPS information.
In the iPhone Photos app, swipe up on a photo; if a map appears, it contains a location. Free CVT's location remover also tells you how many of the processed photos contained GPS data.
The data is cut out without re-saving the photo
Re-saving a photo, as image compression does, removes metadata but also costs a little quality. The location remover cuts only the EXIF, XMP and IPTC segments and comments out of the JPG file and leaves the image data untouched.
With a Nikon sample photo, all 12 EXIF entries (including GPS and camera model) were removed and the pixels were identical to the original. The file only shrank by the removed data, from 158 KB to 143 KB. For PNG, text, EXIF and time chunks are removed.
Why orientation and colour data are kept
Many portrait photos store their pixels sideways and record only a “rotate 90 degrees when shown” value in EXIF. Removing it would make the photo display sideways, so that single orientation value is kept.
The colour profile (ICC) is kept too: removing it can change how some photos look, and it holds no personal information.
What is not removed, and limits
Only the data inside the file is removed; what the photo shows stays. If a window view, a sign, a parcel label or a licence plate gives away the location, crop or cover it.
Only JPG and PNG are processed for now. For iPhone HEIC photos, converting HEIC to JPG drops the location too, so post the JPG afterwards. Your original is not changed, so keep it if you need the data.
Keep the original and check the content, size and format of the result.