Video and audio are difficult formats for anonymity.
Inside the file, recording date and time, device information, location information, editing software, and tag information may remain. In addition, the video or audio content itself contains clues such as faces, voices, backgrounds, notifications, environmental sounds, conversations, and locations.
They contain more information than images, and identity or daily activity area may be inferred from just a few seconds of video or audio.
This article organizes the information that remains in video and audio files and the points to check before publication.
Information remaining in video
Video files have both metadata and video content.
Information
What it shows
Notes
Shooting date and time
When it was recorded
Connects to activity time or on-site participation
Location information
Shooting location
GPS may remain
Device information
Model or app used
Becomes a clue about the recording environment
Editing software
Work environment
Editor or production environment becomes visible
Video content
Faces, background, signs
Not erased by metadata removal
In video, even information visible in only one frame can become a clue.
Momentary notifications and reflections also need checking.
Information remaining in audio
Audio files may retain tag information and information about the recording environment.
The audio itself is also a strong clue. Voice, way of speaking, dialect, background sound, station announcements, workplace sounds, family voices, and notification sounds may be included.
Information
What it shows
Notes
ID3 tags
Title, creator, comment
May remain even in non-music recordings
Recording time
Time recorded
Connects to activity time
Recording app
Usage environment
Clue about device or work environment
Person's voice
Identity
Strong clue for acquaintances
Background sound
Place and situation
Station, shop, workplace, or home becomes visible
Audio can reveal identity even without showing a face.
For high-risk communication, think carefully about publishing audio itself.
Metadata removal alone is not enough
For video and audio, the content remains even if metadata is removed.
Target
Information remaining in content
Example
Video
Background, face, text, reflection
Signs, name badges, notifications
Audio
Voice, environmental sound, conversation
Station announcements, family voices
Screen recording
Tabs, notifications, account names
Real-name email, calendar
Subtitles
Names, times, places
Includes errors in auto-generated subtitles
Editing
Forgotten cuts, margins before and after
Conversations before and after recording
For anonymity, check file-internal information and content separately.
Pre-publication check
Before publishing video or audio, the basic rule is not to release the original file directly.
Check item
Reason
Create a publication copy
Protect the original file
Check metadata
See shooting time and device information
Play the entire file and check
Find momentary leaks
Check audio separately
Listen for background sounds and conversations
Look at subtitles and automatic transcription
Check whether names or places appear
Check filename
Avoid real names and case names
Even in short videos, unnecessary information may appear at the beginning or end.
Recheck after cutting as well.
The decision not to publish is also necessary
Video and audio can be difficult to make completely safe even after processing.
Even if you change a voice, manner of speaking and background sound remain. Even if you hide a face, clothing and location remain. Even if metadata is removed, on-screen notifications and conversations remain. In such cases, not publishing is the safest choice.
Situation
Reason not to publish
Alternative
Voice of the person or people involved is included
Acquaintances can recognize it
Transcribe and organize the content
Location appears strongly
Identified from background
Explain without location information
Minors or family members appear
Involves people other than yourself
Do not use images or audio
Workplace sounds or internal conversations are included
Organization or people involved become visible
Limit to a trusted consultation destination
Processing breaks the meaning
Causes misunderstanding or evidence problems
Store original and create separate publication material
For anonymity, not only the technique for releasing, but also the decision not to release is important.
For high-risk material, consider giving it to a trusted consultation destination through a safe route rather than posting it publicly.
What tools can and cannot check
ExifTool and ffmpeg-related tools may be used to check video and audio metadata.
ExifTool is a representative tool that can check metadata across multiple formats.
However, you need to check the audio and video content yourself.
Longer files are harder to check
Video and audio become harder to check as they get longer.
Even in a 10-minute video, a notification may appear for only one second. Even in 30 minutes of audio, a family voice or station announcement may appear in the middle. For anonymity, it is important not to publish without checking the whole file.
Problem
What happens
Forgotten cuts at beginning or end
Conversations before or after recording remain
Notification in the middle
Real name or contact appears
Background sound
Place or time becomes visible
Subtitles
Names appear through automatic transcription
Editing mistake
Areas thought to be hidden remain
Also check the purpose of publishing the video or audio.
The judgment changes depending on whether it is necessary as evidence, helps explanation, or merely conveys atmosphere. If the purpose is weak, explaining in text is safer.
Screen recordings have separate risks
Among videos, screen recordings require particular caution.
Screen recordings show browser tabs, bookmarks, notifications, email addresses, logged-in icons, filenames, clocks, and input history. Even if you intend to show only part of a document, the edge of the screen may retain a real-name environment.
Things likely to appear
What becomes visible
Countermeasure
Browser tabs
Sites being viewed and work content
Keep only necessary tabs
Notifications
Real names, contacts, schedules
Turn off notifications
Bookmarks
Hobbies, workplace, admin pages
Use a dedicated browser
Filenames
Case names, personal names
Separate into a publication folder
Clock
Recording time and life rhythm
Crop if necessary
Screen recording hands over the state of the device as-is.
If anonymity matters, record in a separate browser or separate user environment prepared for publication, not in your usual environment. After recording, recheck not only the video, but also the audio, subtitles, and filename.
Summary
Video and audio files have risks in both metadata and content.
In addition to recording date and time, location information, device information, editing software, and tag information, faces, backgrounds, reflections, voices, environmental sounds, notifications, and conversations become clues.
Even if metadata is removed, the contents of video and audio remain.
Before publication, create a publication copy and check metadata, video, audio, subtitles, and filename.
For high-risk activity, deciding not to release video or audio can also be a safety measure.
Related tools
Metadata inspection
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.