How Photo Metadata Changes in Signal Messenging App (Tested Results)

Through our testing, we showed that Signal app does indeed, stripped and removed all EXIF Metadata from our photos when we send and received them

Signal, the messaging app supported by both Android and iOS platforms, saw a huge rise in downloads in early January 2021. This came after Whatsapp announced that it would make its users share some personal data with its parent company, Facebook.

Privacy-conscious individuals found further confidence in Signal, especially when Elon Musk and Edward Snowden both gave the app confidence in their respective tweets.

This article will cover the actual testing done on the Signal app regarding how it handles our photos metadata and how much of the metadata is actually removed.

Besides Signal, we also did extensive testing on these following instant messaging apps;

Setting Up The Test Environment

Two Mobile Phones

Two separate mobile phones, each having their own Signal accounts were setup for this experiment.

Phone A will act as the Sender of the photo

Phone B will act as the Receiver

Taking A Photo containing EXIF data

Phone A took a photo with its camera app, with the purpose of capturing full EXIF metadata.

The configurations were toggled on;

System settings > GPS Location ON
Camera app settings > Permission granted for the camera app to use phone’s location
Camera app settings > Allow location to be saved by Camera app

Phone A then sends that photo to Phone B via Signal app.

The Difference in Signal Photo Metadata

EXIF Data on Photo	Before Sending (in Phone A)	After Sending (in Phone B)
Filename	IMG_20210602_133719.jpg	Changed (signal-2021-06-133938.jpg)
File Size	3991982 bytes (3.99 MB)	Reduced 302879 bytes (0.3 MB)
GPS Location (Coordinates, Timestamp)	Yes	Removed
Make & Model of Device Used	Yes	Removed
Image Height & Width	3456 x 4608	Reduced (2048 x 1536)
EXIF Details (Aperture, Brightness, Exposure, Mode, ISO, Flash, etc.)	Yes	Removed
Photo Creation Timestamp	Yes, named as “Create Date”	No, only has “File Access Date”

Test Conclusion

Filename is changed, to begin with, “signal-yyyy-mm-xxxxx.jpg”. The Day value is removed here while the Year and Month values are preserved.
File Size is reduced. The recipient obtained an approximately 92% reduction of photo size from this experiment.
GPS Location is removed entirely. The recipient has no way to know the GPS coordinates, i.e. the longitude and latitude of the location when the original photo was taken.
Device Make & Model used in taking the original photo is removed.
EXIF Details such as camera settings are removed.
Photo Creation Timestamp is removed from the recipient’s side. The Original Photo has a “Create Date” that only Phone A has. Phone B (receiver) can only see a “File Access Date/Time” value that records the date & time it receives the photo via Signal. Therefore this value is always later than the “Create Date”

Q&A relating to Signal Photo Metadata

Does Signal removes or strips off photo’s EXIF metadata?

Yes, it does removes EXIF metadata from photos that we sent them over to other Signal users.

Based on our testing, values such as GPS locations containing lat/long coordinates, make & model of device used and EXIF details such as Aperture settings, ISO settings, if Flash was used, etc, are removed.

Values such as image size and image height & width are reduced.

The filename value was also changed on the recipient’s end.

Is it possible to send EXIF metadata of a photo to someone in Signal?

No, this is not possible. Signal users have no control over their photos metadata once it gets to Signal servers.

Does it matter if the Signal user is using either Android or iOS mobile device?

It does not matter at all. The testing used in this article was using an Android device and an iPhone device.
The decision to strip off EXIF metadata from photos are entirely on the part of Signal, not the users.