Basics of EXIF and GPS Information
EXIF and GPS metadata in photos can reveal capture time, location, device, and editing environment even when the image looks safe.
When posting a photo, many people look only at what is visible in it.
Whether a face is visible. Whether an address is in the background. Whether a name tag or car license plate can be seen.
Of course, that is important.
However, images can retain information that is not visible on the surface. This includes capture time, camera or smartphone model, editing software, and in some cases GPS location information. This information may be stored as metadata attached to the image file.
If you are thinking about anonymity, check both the "appearance" and the "internal information" of a photo.
This article organizes what EXIF and GPS information are and why they affect anonymity.
The actual check procedure before publishing photos is covered in "EXIF and GPS Checks Before Publishing Photos."
What Is EXIF?
EXIF is capture information that may be included in photo files.
Images taken with smartphones or digital cameras may store capture time, camera model, lens information, orientation, exposure settings, editing software, and similar information. If location recording is enabled, GPS information may also be included.
| Information | What can be known | Effect on anonymity |
|---|---|---|
| Capture time | When it was taken | Connects with posting time or activity history |
| GPS | Capture location | Reveals home, workplace, school, or the site |
| Device model | Smartphone or camera being used | Becomes material for correlation with other images |
| Editing software | Editing environment | The usage environment or work device is inferred |
| Image orientation and size | Capture or editing state | Becomes a clue to the same device or same work process |
Not every image retains the same information.
Some apps and social networks remove metadata at posting time. On the other hand, cloud sharing, file transfer, bulletin boards, and email attachments may leave the original metadata intact.
What matters is not leaving it to the service.
GPS Information Is Especially Dangerous
When GPS information remains, the capture location may be directly visible.
A photo taken at home, a photo of materials at work, a whiteboard photographed at school, a photo taken at a meeting place. Even if the place is not visible from the appearance, GPS data can reveal where it was taken.
| Image | What happens if GPS remains |
|---|---|
| Photo taken at home | A daily-life base is revealed |
| Photo of workplace materials | It connects to affiliation or workplace |
| Event photo | Participation place and time are known |
| Travel photo | Movement history and life patterns are visible |
| Photo taken while reporting | Sources or the scene are inferred |
GPS is strong information even by itself.
When combined with posting time, body text, past posts, and other photos, it also reveals routine places and behavior patterns.
Internal Information May Remain Even When the Image Looks Safe
Even if you blur the background of a photo, the capture place or time may appear if EXIF remains.
Conversely, even if you delete EXIF, a sign in the background, the view outside a window, reflections, clothing, weather, shadows, notifications, or the subject of the photo may reveal the place or time.
| Check target | Information to look at | Point to watch |
|---|---|---|
| Appearance | Faces, background, reflections, signs, name tags | Information visible to the eye |
| Metadata | GPS, capture time, device, editing software | Information not visible from appearance |
| Post text | Place, time, situation description | Combines with the image |
| Posting time | When it was published | Connects with capture time or local information |
For anonymity, either one alone is not enough.
Check both the appearance and the internal information of images.
ExifTool Can Check It
ExifTool is a representative tool for checking image metadata.
ExifTool is a metadata checking and editing tool by Phil Harvey, and it can handle many metadata formats such as EXIF, GPS, XMP, and IPTC. It is used not only for images but also for checking information in a wide range of files such as video and audio.
URL : https://exiftool.org/
The reason for introducing ExifTool is not simply that it is well known. It has been used for a long time, supports a wide range of formats, and can check detailed metadata from the command line.
However, using ExifTool does not make the photo safe by itself. Even if you can check metadata, it does not automatically protect the image appearance, post text, cloud sharing settings, or past information.
Order for Checking
Before publishing a photo, check in the following order.
- Look at the appearance of the image
- Check EXIF and GPS information
- Create a publication copy
- Open it in a different environment and see whether metadata remains
- Check whether there is a problem when combined with the post text and posting time
| Stage | What to check |
|---|---|
| Appearance | Faces, background, reflections, text, place clues |
| Internal information | GPS, capture time, device, editing software |
| Publication copy | Do not publish the original image as-is |
| Recheck | Open it in another app after removal and check |
| Correlation check | See whether it connects with the body text or posting time |
Even when a social network or messaging app removes metadata, it is important to build the habit of checking the original image before upload.
Behavior can change when the posting destination changes.
Do Not Overtrust Service-Side Removal
Some social networks and messaging apps remove image metadata at posting time.
This is convenient, but leaving anonymity to a service is dangerous. The removal scope differs by service. Behavior may also differ between posting something as an image and sending it as a file attachment. With cloud sharing, the original file may be delivered to the other person as-is.
| Sharing method | Point to watch |
|---|---|
| Social network post | Metadata may be removed, but behavior differs by service |
| Messaging app image send | It may be removed through compression or conversion |
| File attachment | Original file metadata may remain |
| Cloud sharing | Often shares the original image as-is |
| Email attachment | File names and metadata tend to remain |
Rather than remembering "this app should remove it," it is more stable to create and check your own publication copy.
Recheck After Removal
Metadata removal is not finished just because you ran it.
Some information may remain even when you think you removed it. Editing apps may add new metadata. When an image is saved again, creation software or save time may be newly added.
After you create a publication copy, check it again.
| What to check | Reason |
|---|---|
| Whether GPS is gone | Location information is often the most dangerous |
| Whether capture time remains | It connects with activity time |
| Whether device names or software names remain | It becomes a clue to the work environment |
| Whether the file name has a problem | Even if metadata is removed, the name can leak information |
| Whether the image appearance contains information | Check clues other than internal information |
Treat checking, removal, and rechecking as one procedure.
Summary
EXIF and GPS information are metadata that may remain inside photos.
Capture time, capture location, device model, editing software, and similar information affect anonymity. GPS information in particular can directly indicate a home, workplace, school, site, or reporting location.
Before publishing a photo, check not only its appearance but also its metadata. Tools such as ExifTool help with metadata checks, but they do not automatically protect image content, post text, posting time, or cloud sharing settings.
For anonymity, it is important to check photos from both "visible information" and "invisible internal information."
Related tools
Google Lens
An external resource related to this article. Open it only when it fits your situation and threat model.
Why it is listed: It can help with the article topic, but it is outside Anonymity Sense and should be checked before use.
URL : https://lens.google/
ExifTool
An external resource related to this article. Open it only when it fits your situation and threat model.
Why it is listed: It can help with the article topic, but it is outside Anonymity Sense and should be checked before use.
URL : https://exiftool.org/
MAT2
An external resource related to this article. Open it only when it fits your situation and threat model.
Why it is listed: It can help with the article topic, but it is outside Anonymity Sense and should be checked before use.