Remove unnecessary Metadata from Files
Summary
| Description | Command |
|---|---|
| Show Metadata | file /path/to/file |
| Show extended Metadata | exiftool /path/to/file -v |
| Update Metadata | exiftool /path/to/file -[TAG]=[VALUE] |
| Remove Metadata | exiftool /path/to/file -[TAG]= |
| Remove ALL unnecessary Metadata | exiftool /path/to/file -*= |
Introduction
When generating data with cameras, word processing, mailing or other programs that create files, the generation program adds extended attributes to a newly created or modified file. These attributes are part of the so-called Metadata. In most cases this information is added to a file without the user being aware of it or ever having to make use of it. Metadata includes the file name, creation date, or file type, which are fairly legitimate, but they can also take the form of the author of a text document, right down to information about the device that created it. In today's world, where digital cameras are built into our mobile devices and photos took with these are shared with our beloved and the rest of the Internet, sharing metadata can be a privacy issue as well, because it can leak information about the user themselves, their hardware or software. When focusing on images, a modern smartphone camera typically stores the device model, camera settings and often the location where the photo was taken, a so-called geotag. However, the last depends on the user's settings, which most inexperienced users will never notice or change. To preserve privacy and prevent the exposure of potentially vulnerable hardware or software, it's worth reassessing the benefits of metadata storage. As for the content of the file itself, it is possible to remove unwanted metadata.
Requirements
On UNIX like systems like GNU-Linux or macOS the command file(man) can be used to list the metadata included with the file. Additionaly when using macOS the command xattr (man) or getxattr (man) for GNU/Linux may reveal some additional metadata used by the operating system.
$ file ./LUPUS_XT2_Plus_PCB_Front.jpg /path/to/file/LUPUS_XT2_Plus_PCB_Front.jpg: JPEG image data, JFIF standard 1.01, resolution (DPI), density 72x72, segment length 16, Exif Standard: [TIFF image data, little-endian, direntries=11, height=1867, manufacturer=samsung, model=SM-G965F, xresolution=164, yresolution=172, resolutionunit=2, software=PhotoScape, datetime=2020:02:24 19:14:16, width=2158], baseline, precision 8, 2158x1867, components 3
Eventhough the metadata is easy to add and view, it is not so easy to remove it. A program that is able to do the job is Phil Harvey's ExifTool an can be installed using common package managers like apt for debian based systems or brew on macOS. Windows user can download the executable from the vendors webpage.
Description
$ exiftool -v LUPUS_XT2_Plus_PCB_Front.jpg ExifToolVersion = 11.85 FileName = LUPUS_XT2_Plus_PCB_Front.jpg Directory = . FileSize = 3950536 FileModifyDate = 1592068395 FileAccessDate = 1592068396 FileInodeChangeDate = 1592068395 FilePermissions = 33188 FileType = JPEG FileTypeExtension = JPG MIMEType = image/jpeg JPEG APP0 (14 bytes): + [BinaryData directory, 9 bytes] | JFIFVersion = 1 1 | ResolutionUnit = 1 | XResolution = 72 | YResolution = 72 | ThumbnailWidth = 0 | ThumbnailHeight = 0 JPEG APP1 (842 bytes): ExifByteOrder = II + [IFD0 directory with 11 entries] | 0) ImageWidth = 2158 | 1) ImageHeight = 1867 | 2) Make = samsung | 3) Model = SM-G965F | 4) XResolution = 72 (72/1) | 5) YResolution = 72 (72/1) | 6) ResolutionUnit = 2 | 7) Software = PhotoScape | 8) ModifyDate = 2020:02:24 19:14:16 | 9) YCbCrPositioning = 1 | 10) ExifOffset (SubDirectory) --> | + [ExifIFD directory with 36 entries] | | 0) ExposureTime = 0.02 (1/50) | | 1) FNumber = 2.4 (240/100) | | 2) ExposureProgram = 2 | | 3) ISO = 160 | | 4) ExifVersion = 0220 | | 5) DateTimeOriginal = 2020:02:24 19:14:16 | | 6) CreateDate = 2020:02:24 19:14:16 | | 7) ComponentsConfiguration = 1 2 3 0 | | 8) ShutterSpeedValue = 5.64 (564/100) | | 9) ApertureValue = 2.52 (252/100) | | 10) BrightnessValue = 2.36 (236/100) | | 11) ExposureCompensation = 0 (0/10) | | 12) MaxApertureValue = 1.16 (116/100) | | 13) MeteringMode = 2 | | 14) Flash = 0 | | 15) FocalLength = 4.3 (430/100) | | 16) UserComment = | | 17) SubSecTime = 0020 | | 18) SubSecTimeOriginal = 0020 | | 19) SubSecTimeDigitized = 0020 | | 20) FlashpixVersion = 0100 | | 21) ColorSpace = 1 | | 22) ExifImageWidth = 2158 | | 23) ExifImageHeight = 1867 | | 24) InteropOffset (SubDirectory) --> | | + [InteropIFD directory with 2 entries] | | | 0) InteropIndex = R98 | | | 1) InteropVersion = 0100 | | 25) SceneType = . | | 26) CustomRendered = 0 | | 27) ExposureMode = 0 | | 28) WhiteBalance = 0 | | 29) DigitalZoomRatio = undef (0/0) | | 30) FocalLengthIn35mmFormat = 26 | | 31) SceneCaptureType = 0 | | 32) Contrast = 0 | | 33) Saturation = 0 | | 34) Sharpness = 0 | | 35) ImageUniqueID = I12LLKF00SM JPEG DQT (65 bytes): JPEG DQT (65 bytes): JPEG SOF0 (15 bytes): ImageWidth = 2158 ImageHeight = 1867 EncodingProcess = 0 BitsPerSample = 8 ColorComponents = 3 YCbCrSubSampling = 2 2 JPEG DHT (29 bytes): JPEG DHT (179 bytes): JPEG DHT (29 bytes): JPEG DHT (179 bytes): JPEG SOS
-v) or the multilanguage support (-lang [COUNTRYCODE]).In this example scenario, I'd like to remove the Make (Camera Vendor), Model (Camera Model), Software (second stage editing tool), ImageUniqueID metadata as well as all timestamps from the example photo. To write or delete metadata, tag values are assigned using -TAG=[VALUE], and/or the -geotag options. Additionally I'm going to do this operation for a bulk of photos.
-v option to display the correct tag names used for modification or deletion!$ exiftool LUPUS_XT2_Plus_*.jpg -Make= -Software= -Model= -ImageUniqueID=
# Update multiple files at the same time $ exiftool LUPUS_XT2_Plus_*.jpg -Comment="Hello darkness my old friend" # Always update timestamps last $ exiftool LUPUS_XT2_Plus_*.jpg -CreateDate="1970:01:01 00:00:00" -DateTimeOriginal="1970:01:01 00:00:00" -ModifyDate="1970:01:01 00:00:00"
$ exiftool LUPUS_XT2_Plus_PCB_Back.jpg ExifTool Version Number : 11.85 File Name : LUPUS_XT2_Plus_PCB_Back.jpg Directory : . File Size : 3.2 MB File Modification Date/Time : 2020:06:13 20:30:20+02:00 File Access Date/Time : 2020:06:13 20:30:22+02:00 File Inode Change Date/Time : 2020:06:13 20:30:21+02:00 File Permissions : rw-r--r-- File Type : JPEG File Type Extension : jpg MIME Type : image/jpeg JFIF Version : 1.01 Exif Byte Order : Little-endian (Intel, II) X Resolution : 72 Y Resolution : 72 Resolution Unit : inches Modify Date : 1970:01:01 00:00:00 Y Cb Cr Positioning : Centered Exposure Time : 1/50 F Number : 2.4 Exposure Program : Program AE ISO : 200 Exif Version : 0220 Date/Time Original : 1970:01:01 00:00:00 Create Date : 1970:01:01 00:00:00 Components Configuration : Y, Cb, Cr, - Shutter Speed Value : 1/50 Aperture Value : 2.4 Brightness Value : 1.99 Exposure Compensation : 0 Max Aperture Value : 1.5 Metering Mode : Center-weighted average Flash : No Flash Focal Length : 4.3 mm User Comment : Sub Sec Time : 0456 Sub Sec Time Original : 0456 Sub Sec Time Digitized : 0456 Flashpix Version : 0100 Color Space : sRGB Exif Image Width : 2158 Exif Image Height : 1867 Interoperability Index : R98 - DCF basic file (sRGB) Interoperability Version : 0100 Scene Type : Unknown (.) Custom Rendered : Normal Exposure Mode : Auto White Balance : Auto Digital Zoom Ratio : undef Focal Length In 35mm Format : 26 mm Scene Capture Type : Standard Contrast : Normal Saturation : Normal Sharpness : Normal Comment : Hello darkness my old friend Image Width : 2158 Image Height : 1867 Encoding Process : Baseline DCT, Huffman coding Bits Per Sample : 8 Color Components : 3 Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2) Aperture : 2.4 Image Size : 2158x1867 Megapixels : 4.0 Scale Factor To 35 mm Equivalent: 6.0 Shutter Speed : 1/50 Create Date : 1970:01:01 00:00:00.0456 Date/Time Original : 1970:01:01 00:00:00.0456 Modify Date : 1970:01:01 00:00:00.0456 Circle Of Confusion : 0.005 mm Field Of View : 69.4 deg Focal Length : 4.3 mm (35 mm equivalent: 26.0 mm) Hyperfocal Distance : 1.55 m Light Value : 7.2
_original.Maximus Paranoism
A camera pro may be able to still identfy the camera or the type of device by the remaining metadata. For the more paranoid, consider removing ALL metadata using -*= and you may also want to change local creation, modification, access file timestamps using touch. Read the article Linux – Fake File Access, Modify and Change TimeStamps for more information.
$ exiftool LUPUS_XT2_Plus_PCB_Back.jpg -*= $ exiftool LUPUS_XT2_Plus_PCB_Back.jpg ExifTool Version Number : 11.85 File Name : LUPUS_XT2_Plus_PCB_Back.jpg Directory : . File Size : 3.2 MB File Modification Date/Time : 2020:06:13 20:35:41+02:00 File Access Date/Time : 2020:06:13 20:36:03+02:00 File Inode Change Date/Time : 2020:06:13 20:36:02+02:00 File Permissions : rw-r--r-- File Type : JPEG File Type Extension : jpg MIME Type : image/jpeg Image Width : 2158 Image Height : 1867 Encoding Process : Baseline DCT, Huffman coding Bits Per Sample : 8 Color Components : 3 Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2) Image Size : 2158x1867 Megapixels : 4.0
References