MHT / MHTML file format
.mht · .mhtml · archive (web page) · introduced 1999 by Microsoft
What is a MHT / MHTML file?
MHTML is a single-file web page archive defined as a MIME multipart message — exactly like a saved email with image attachments. Every browser ever shipped by Microsoft can save and open MHT, and Chrome supports it through chrome://flags. It is convenient for archiving an entire web page including images and stylesheets in one file.
Most readers reach this page after double-clicking a .mht file and finding their operating system unsure what to do with it. The good news: MHT / MHTML is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.
How to extract a MHT / MHTML file
Opening a .mht file is straightforward on every modern operating system. The exact steps depend on which platform you are on:
On Windows
- Locate the
.mhtfile in File Explorer. - Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
- If prompted, pick a destination folder and click Extract.
- The extracted files appear in a folder next to the original archive.
On macOS
- Find the
.mhtfile in Finder. - Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
- Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
- The extracted folder appears next to the archive.
On Linux
- Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).
- On the command line, run one of:
7z x archive.mht # works for almost any format
- The files appear in the current directory.
How to create a MHT / MHTML file
To pack files into a .mht archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write MHT / MHTML.
On the command line, the canonical create command is:
# Use 7-Zip, PeaZip, or the format's reference tool to create .mht files.
If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.
Strengths
- Single file
- Email-style structure
- Wide browser support
Weaknesses and limitations
- JavaScript and dynamic content do not always survive
- Less popular than .webarchive on Mac
Typical use cases
- Single-file web page archive
- Offline reading
- Email-like web snapshots
Technical details
MHT / MHTML uses the MIME multipart algorithm and is identified on disk by the magic byte sequence 46 72 6F 6D 3A. The standard MIME type is multipart/related. The format is an open specification and is free for any use.
Frequently asked questions
Is MHT / MHTML safe to open?
Archive files are containers — they are only as safe as what they contain. A .mht from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.
What is the maximum file size?
Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).
Can I password-protect a MHT / MHTML?
Some archivers can wrap MHT / MHTML files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.
How does MHT / MHTML compare to other formats?
See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.