.MHTML File Extension Reference
The .MHTML file format is a structured digital document and data container standardized for cross-platform exchange and application interoperability. Files with the .MHTML extension are categorized under Documents and are widely utilized in modern computing environments for storing, rendering, and exchanging structured data. By verifying the header signature (50 4B 03 04) using forensic byte inspection tools, users can authenticate file integrity and rule out disguised executable payloads.
Quick Specification & Metadata
.MHTML
Documents
multipart/related
IETF MIME / RFC 2557 ecosystem
N/A
Proprietary / Patent Licensed
Binary Header Data
100 KB - 20 MB
Online .MHTML Viewer & Live Inspector
Open, inspect, zoom, and export .MHTML files directly in your web browser. 100% private in-memory processing.
Drop your .MHTML file here or browse
Inspect and preview any .MHTML file securely with zero server uploads.
What is a .MHTML File? (Technical Definition & Architecture)
The .MHTML file format is a structured digital document and data container standardized for cross-platform exchange and application interoperability. Files with the .MHTML extension are categorized under Documents and are widely utilized in modern computing environments for storing, rendering, and exchanging structured data. By verifying the header signature (50 4B 03 04) using forensic byte inspection tools, users can authenticate file integrity and rule out disguised executable payloads.
Organizes body paragraphs, styles, table schemas, and embedded media assets.
Preserves font embedding, line spacing, margins, and print pagination.
Encapsulates document modification metadata, comments, and change tracking.
MHTML Binary Structure & Header Specifications
The .MHTML format organizes data into validated sequential or hierarchical byte structures. Inspecting the header offset reveals the magic byte sequence 50 4B 03 04.
- File Signature (Magic Bytes): 50 4B 03 04
- MIME Content-Type: multipart/related
- Payload Structure: Optimized data stream with metadata headers and checksum records.
- Safety Classification: Medium Risk – MHTML may preserve scripts, external links, and embedded content; inspect untrusted archives before opening them in a browser or office application Files ending in .MHTML should always be inspected for valid magic bytes to verify they match legitimate Documents specifications.
How to Open .MHTML Files on Windows, Mac & Android
- 1Primary Application: Double-click or open directly with Microsoft Edge.
- 2Alternative Software: Open using Microsoft Word.
- 3File Association: Right-click the file, select Open with > Choose another app, and check Always use this app.
- 1Native macOS Application: Open with Microsoft Edge.
- 2Quick Look Preview: Highlight the file in Finder and tap the Spacebar.
- 3Set Default App: Press Cmd + I, expand Open with, select your application, and click Change All.
- 1Compatible Mobile Apps: Download a dedicated viewer for .mhtml from the Google Play Store.
- 2Cloud Storage: Open through Google Drive, Dropbox, or OneDrive mobile apps.
- 3Online Browser Conversion: Use AnyFileX mobile browser tools to convert the file into universal PDF or image formats.
Convert .MHTML Files Online & Free
Convert your .MHTML files directly into standardized .PDF format with high precision and zero privacy compromises.
Export .MHTML files to .JPG for universal cross-platform viewing, printing, and sharing.
.MHTML MIME Types & HTTP Server Headers
When serving .mhtml files over HTTP or configuring REST APIs, web servers must send the official IANA registered Content-Type headers:
| MIME Type Identifier | Standard Usage | File Extensions | Copy |
|---|---|---|---|
| multipart/related | Standard official MIME type for .mhtml files | .mhtml |
# Nginx mime.types
types {
multipart/related mhtml;
}
# Apache .htaccess
AddType multipart/related .mhtml.MHTML Magic Bytes & Hex File Signatures
In digital forensics and file signature analysis, authentic .mhtml files begin with a standardized magic byte sequence at byte offset 0x00 to verify file integrity and prevent extension spoofing:
Offset 0x0050 4B 03 04MHTMLDocuments File Format.MHTML vs .PDF (Detailed Format Comparison)
| Feature Metric | .MHTML | Advantage | |
|---|---|---|---|
| Format Full Name | MHTML File Format | Portable Document Format | Tie / Equal |
| Category | Documents | Documents | Tie / Equal |
| MIME Content-Type | multipart/related | application/pdf | Tie / Equal |
| Binary Header (Magic Bytes) | 50 4B 03 04 | 25 50 44 46 2D (%PDF-) | Tie / Equal |
| Typical Storage Footprint | 100 KB - 20 MB | 200 KB – 25 MB | Tie / Equal |
| Universal Native Support | High / OS Standard | High / OS Standard | Tie / Equal |
.MHTML Compatibility Matrix
Supported natively or through Microsoft Edge
Supported natively or via Microsoft Word
Supported via open-source tools and command line utilities
Accessible through compatible mobile viewers or cloud previewers
Supported through dedicated mobile apps or cloud viewers
Accessible via web browser applications and Chrome extensions
Recommended Software for .MHTML
Microsoft Edge
IETF MIME / RFC 2557 ecosystem
Microsoft Word
IETF MIME / RFC 2557 ecosystem
Compatible web browsers
IETF MIME / RFC 2557 ecosystem
Text editors and MIME tools
IETF MIME / RFC 2557 ecosystem
Common Errors & Troubleshooting .MHTML Files
Security & Malware Risk Assessment
Can a .MHTML file carry viruses or malware?
MHTML may preserve scripts, external links, and embedded content; inspect untrusted archives before opening them in a browser or office application Files ending in .MHTML should always be inspected for valid magic bytes to verify they match legitimate Documents specifications.
May support scripting or automation macros
Safe to inspect with AnyFileX's browser sandbox
- •Verify file extension in OS File Explorer options ('Show known file extensions').
- •Verify magic bytes (50 4B 03 04) to ensure the file isn't a renamed executable.
- •Do not open .MHTML attachments received unexpectedly via email or instant messenger.
Frequently Asked Questions
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