Find the real format
Identify images, video, audio, documents, archives and more by their contents—even when the extension is missing or wrong.
Coming to Mac, iPhone & iPad
What is this
file, really?
A filename doesn’t tell the whole story.
File Sniff looks inside to reveal the real file type, spot mismatched extensions, and clear up the mystery.
On-device analysis. Your files stay with you.
66 74 79 70Look a little closer.
.pdf?holiday.pdf
Sniffed it outActually, an MP4 video.
Identifies by content
Spots extension mismatches
Analyses locally
Got a mystery file right now?
Give it a sniff in your browser. Free, local, and no sign-up.
Names can be misleading.
The bytes tell the story.
A video wearing a PDF extension? A Word document hiding in a ZIP?
File Sniff helps you see what you’re actually working with.
Pick a sample file below
File name Detected type
Inside the file
MP4 video
video/mp4.pdf → .mp4
The name says PDF. The file’s internal signature says MPEG-4 video.
File signature
00 00 00 20 66 74 79 70
69 73 6F 6D 00 00 02 00Illustrative sample results. File analysis happens in the app, on your device.
Less guessing.
More getting on
with things.
For the mystery attachment, the stubborn download, and the folder full of “what’s this?”
Look beneath the surface
Inspect file signatures and image metadata. Read embedded Content Credentials and AI-origin declarations where present.
Make sense of a whole folder
Scan files together, filter for extension mismatches, and export results as CSV or JSON to keep or share.
Take the next step on Mac
Fix a mismatched extension with a confirmed, undoable rename. Convert Outlook .msg messages to .eml files for Apple Mail.
Mac-only toolsYour files. Your device.
Local analysis, by default.
File Sniff analyses locally, without uploading your files. Inspection leaves originals untouched. Optional external checks open in your browser, only when you choose them.
Read about privacyCurious about files.
Respectful of yours.
Respectful of yours.
Made for the things you’d rather
not upload to a website.
From everyday files
to unusual suspects.
Look beyond the extension with support for familiar formats and the containers that hide them.
And when a format isn’t recognised, you get an honest “Unknown”. Learn how to investigate an unknown file.
A few things
you might wonder.
How is this different from looking at the extension?
An extension is part of a filename and can be changed. File Sniff reads signatures and container information inside the file to identify its actual format. That’s how it can recognise an MP4 video named .pdf.
Does File Sniff tell me if a file is safe?
No. File Sniff identifies formats and flags extension mismatches. It isn’t an antivirus scanner, and a matching extension doesn’t prove a file is safe.
Can it tell whether an image was made with AI?
It can show embedded Content Credentials and metadata that declares AI-generated origin. It doesn’t give an “AI or not” verdict. Missing metadata proves nothing: screenshots and re-encoding can remove it.
Will it change any of my files?
Analysis is read-only. On Mac, Fix Extension renames a file only after confirmation and supports Undo. Converting a message or exporting results creates a file where you choose.
Which devices will it run on?
File Sniff is being prepared for the Mac App Store and the App Store for iPhone and iPad. The current apps require macOS 14 or later, or iOS / iPadOS 17 or later. Extension repair and Outlook message conversion are Mac-only.
Why won’t my file open even with the right extension?
A file may be incomplete, damaged, or unsupported by the app opening it. File Sniff can flag some incomplete files and help identify their format, but it does not repair damaged content.
A good nose for files.
A small, native app for those little digital mysteries.
In the works. Store links and pricing will be added at launch.