Remove EXIF and GPS Data by Re-Encoding the Image

A JPEG is a container. Alongside the compressed image data it holds a set of metadata segments, and EXIF is the largest of them. A typical phone photo records the camera make and model, the lens, the exposure settings, the orientation, the timestamp with sub-second precision, the software used to edit it, and — when location services were on — the GPS latitude, longitude, altitude, and a timestamp for the fix.

Some cameras and phones also write a thumbnail into the EXIF block. That thumbnail is a separate, unedited copy of the image. A photo that has been cropped to remove something at the edge can still carry a thumbnail of the uncropped original.

PNG has its own metadata chunks, and the same category of data can appear there. Screenshots usually carry much less than camera photos, but they are not guaranteed to carry nothing.

Metadata lives in the container, not in the pixel data. When you draw an image onto a canvas and export it, the browser reads the decoded pixels and writes a new file from those pixels. The original container is not copied or consulted. There is no step in that path where EXIF could be carried across, because the code that writes the new file never sees the old metadata.

This is why the operation is reliable rather than best-effort. It is not a metadata-stripping filter that has to know about every possible tag; it is a rebuild that starts from pixels alone.

The same mechanism explains a second effect: a newly encoded file is also a newly compressed file. For JPEG, that means a generation of quality loss. For PNG, which is lossless, it means no loss but often a larger file.

Cropping is a common way to remove something from the edge of a photo. It changes the pixel data and leaves the container intact, which means the embedded thumbnail and the GPS block are still there, describing the uncropped original.

This is a genuinely counterintuitive failure: the visible image is clean and the file is not. It is also invisible to any review that looks at the picture rather than the metadata.

Rebuilding from a canvas avoids it, because the thumbnail is metadata. There is no thumbnail in a file that was encoded from pixel data by a browser.

On a desktop, `exiftool` prints every metadata field a file contains, including GPS and the embedded thumbnail. It is the most direct check and it is free.

Without command-line tools, most operating systems will show a subset in the file's properties or Get Info dialog — usually camera and date, sometimes location. Look for a 'location' or 'GPS' line specifically.

A quick structural test: if a JPEG's file size barely changes after an edit that should have altered a large region, the edit may have been applied as a layer rather than baked into the pixels. A rebuilt file usually changes size noticeably, because it was recompressed from scratch.