Practical file & metadata guides
Understand your files
Practical guides to unknown file types, magic bytes, AI Content Credentials, Office metadata and photo privacy.
A filename extension is only a label. Whether you are trying to open a mystery download, check if an image or Office document discloses AI use, or strip GPS coordinates from a photo before sharing it, the real answers live inside the file’s structure.
These guides explain what formats and metadata actually record, how container files like .docx, .xlsx, .heic and winmail.dat work under the hood, and what file inspection can—and cannot—prove. Every guide pairs with a free browser tool that inspects or cleans files locally on your device without uploading them anywhere.
File types, signatures & containers
Identify unknown files from their magic bytes, spot extension mismatches, and unpack container formats. · File type checker
- How to identify an unknown file type
Find out what a file is when it has no extension, the wrong extension, or refuses to open. Learn what file signatures can—and cannot—tell you.
- What does a file extension mismatch mean?
Understand why a file’s extension can disagree with its contents, when renaming helps, and why changing an extension does not convert a file.
- File Signatures & Magic Bytes Guide
Learn how file signatures (magic bytes) and container headers identify real file formats like PDF, PNG, HEIC, ZIP and Office documents.
- What Is a .dat File and How to Open It
Find out why .dat files have no single format, how to identify what is actually inside a .dat file, and how to extract Outlook winmail.dat attachments.
- How to Open an Outlook .msg File on a Mac (Without Uploading Private Emails)
Learn why macOS and Apple Mail cannot open Windows Outlook .msg files natively, how .msg differs from .eml and winmail.dat, and how to open or convert .msg files locally.
AI evidence, C2PA & document metadata
Understand Content Credentials, EXIF/XMP AI declarations, MCP agent tools, and what Word, Excel and PowerPoint files record. · AI evidence & metadata checker
- How to Tell if an Image Is AI-Generated
Learn what actually works for checking AI images—C2PA Content Credentials, IPTC DigitalSourceType and EXIF/PNG metadata—and why percentage detectors fail.
- How to Check Whether an Image Discloses AI Use
Learn what C2PA Content Credentials reveal about AI-generated images, how to interpret validation results, and why missing metadata proves nothing.
- Inspect Word, Excel & PowerPoint Metadata
See how Word, Excel and PowerPoint OOXML files store author history, hidden sheets, templates and automation or AI clues inside ZIP parts.
- File Sniff MCP Server: Magic-Byte & AI Provenance Tools for Claude, Cursor & AI Agents
Connect Claude Desktop, Claude Code, Cursor or any Model Context Protocol (MCP) client to File Sniff via our zero-install Remote HTTP endpoint or local stdio server.
Photo privacy, EXIF & image formats
Strip GPS location and camera details without losing quality, and understand HEIC, WebP and JPG. · Remove image metadata
- How to Remove EXIF & GPS Photo Metadata
Learn what hidden EXIF, GPS location, XMP and Content Credentials data photos carry, and how to remove metadata without losing image quality.
- HEIC vs JPG: What’s Actually Inside the File
Compare iPhone HEIC and JPG photo formats: HEIF containers, HEVC compression, Display P3 wide colour, metadata and why renaming .heic to .jpg fails.
Ready to inspect a file?
Try our free browser tools—or explore the native File Sniff app for Mac, iPhone and iPad.