What is ExifTool?
Learn how ExifTool helps check metadata in images, PDFs, videos, Office documents, and similar files locally before publication.
ExifTool is a widely used tool for checking and editing metadata contained in images, videos, PDFs, Office documents, and similar files.
When thinking about anonymity, information left inside files is easy to overlook.
Date and time a photo was taken. GPS location information. Camera model. PDF creator. Company name in an Office document. Editing software information.
ExifTool is often used as an entry point for checking this kind of information.
The reason for introducing ExifTool is that it lets you check metadata in a wide range of formats, including images, videos, PDFs, and Office documents, on your own device. The important point is that you can check files where anonymity matters without uploading them to an unfamiliar online removal service. Supported formats and download information need to be checked on the official site. URL : https://exiftool.org/
What can you learn with ExifTool?
With ExifTool, you can check metadata contained in a file.
| File | Information that may be checkable |
|---|---|
| Photo | Date and time taken, GPS, camera model, lens information |
| Video | Date and time recorded, device information, location information, software information |
| Creator, title, creation software, creation date and time | |
| Office document | Author, company name, edit date and time, app information |
| Audio | Recording date and time, tags, software information |
The information you can see differs by file format. Also, not every file contains the same information.
What matters is building the habit of checking before publication.
The information shown by ExifTool is one part of the clues left in the file. If the date and time taken, GPS, creator, or editing software appears, you can judge that information before publication. On the other hand, even if no dangerous information is displayed, safety is not guaranteed. Check the image background, audio content, document text, and filename separately.
In anonymity work, treat tool results as material for checking. Read the information the tool finds and judge what connects to whom.
The meaning of local checking
ExifTool can check files in your own environment.
This is important. If you upload a file to a web service you do not understand well in order to check metadata, you hand the file to an external party at that point.
The more important anonymity is for a file, the more carefully the checking process itself needs to be handled.
A tool that can check locally gives you an option to avoid external upload.
Online metadata checking services are convenient. However, if you upload high-risk images or documents, the checking process itself becomes a new act of sharing. For reporting materials, whistleblowing materials, photos from activity sites, and files containing personal information, handing them to an external site for checking is itself a risk.
If you use a local tool such as ExifTool, you can check the file on your own device. Of course, the local environment itself also needs to be safe. If you check in a real-name cloud sync folder or on a workplace device, other histories may remain.
Information that can be removed and information that remains
ExifTool can be used to check and remove metadata. However, using ExifTool does not make everything safe.
Even if you remove metadata, the image background, reflections, signs, uniforms, document text, and filename remain.
| Target | Easy to handle with ExifTool? | Caution |
|---|---|---|
| Date and time taken | Easy to handle | Recheck after removal |
| GPS information | Easy to handle | Place clues inside the image remain |
| Creator information | May be manageable | Differs by file format |
| Image background | Cannot be handled | Visual checking is needed |
| Specific information in the text | Cannot be handled | Content checking is needed |
| Filename | Check separately | Names and case names often remain |
ExifTool is a tool for checking metadata. It is not a tool that guarantees anonymity as a whole.
Especially with PDFs, even if you change the displayed information with ExifTool, the original metadata may remain inside the file. For PDFs, also check procedures suited to the format, such as qpdf or regeneration.
It is important not to misunderstand this point. Even if you remove GPS with ExifTool, the place is visible if a station name appears in the photo. Even if you remove creator information, the source is visible if a document number or internal term remains. Even if you remove the date and time taken, the period may be inferred from an event sign or weather.
Metadata removal is necessary work. However, in an anonymity check, look at metadata, appearance, document text, filenames, and sharing paths together.
Checking flow
When using ExifTool, check in the following flow.
- Copy the original file under a different name
- Check metadata with ExifTool
- Read the information that remains
- Remove unnecessary metadata
- Recheck the file after removal
- Also check the appearance of the image or document text
Rechecking after removal is important. Depending on the file format or editing software, new information may be attached when saving.
Also understand why you keep the original file. In whistleblowing and reporting materials, the original file may be important as evidence. If you directly overwrite the original file, you may not be able to check it later. For that reason, separate the original file, the working copy, and the publication copy.
| File | How to handle it |
|---|---|
| Original file | Store safely for evidentiary value and rechecking |
| Working copy | Use for metadata checking and removal work |
| Publication copy | Recheck after removal, then publish or share |
What to decide before using it
When using ExifTool, pay attention to the following points.
- Work while keeping the original file
- Always recheck the file after removal
- Check not only metadata but also visible content
- Check the filename and sharing destination too
- Do not upload high-risk files to online checking services
Especially for whistleblowing, reporting materials, and activist materials, file checking itself is part of operations.
This article does not go deep into how to use ExifTool itself. What matters here is understanding when to use the tool and where its limits are. You need to check the official site or another article for how to run commands, removal options, and supported formats.
If unknown items appear in the checking results, look up what they mean. If you ignore items you do not understand and publish, unexpected information may remain. For high-risk files, it may also be necessary to have someone knowledgeable or a trusted support contact check them.
What to look at after using ExifTool
After checking with ExifTool, do not stop at looking at the results. Look at whether the remaining items connect to a person, place, device, organization, or time. If you removed information, check the file after removal once more.
| What to look at after checking | Reason |
|---|---|
| Recheck after removal | New information may be attached when saving |
| Filename | The name remains even if metadata is removed |
| Images and text | Backgrounds and content are not removed by ExifTool |
| Sharing destination | Do not send it to a real-name cloud or broad sharing area |
| Original file | Pay attention to evidentiary value and accidental publication |
ExifTool is an entry point for checking work. In the end, a human judges "who does this information lead back to?"
Summary
ExifTool is a representative local tool for checking and editing file metadata.
It becomes an entry point for checking the date and time taken, location information, creator, and software information left in photos, videos, PDFs, Office documents, audio files, and similar files.
However, ExifTool does not automatically make a file anonymous. The image background, document text, filename, sharing path, and cloud history need to be checked separately.
ExifTool is a tool that supports pre-publication checking. After using it, it is important to recheck and always look at clues other than metadata too.
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.
qpdf
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.
FFmpeg
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://ffmpeg.org/