What is a .mht file?
A .mht file is an email message. Its registered MIME type is message/rfc822, which places it in the email or message family of formats.
Technically it is a specialised form of text/plain (the .asc format), so tools that understand that format can often read at least part of it.
MHT is a text-based format: the contents are readable characters, so any text editor can open it, and it compresses well.
The same format is also saved with the extensions .eml, .mhtml, .mime.
MHT file format details
| Extension | .mht |
|---|---|
| Format | Email message |
| MIME type | message/rfc822, application/x-mimearchive |
| Category | Email or message |
| Text or binary | Text |
| Based on | text/plain |
| File signature | None fixed |
| Registered with IANA | Yes |
| Other extensions | .eml, .mhtml, .mime |
How to open MHT files
| Windows | MHT files are plain text, so Notepad opens them: right-click the file, choose Open with, then Notepad. Notepad++ and VS Code are free and show long files more comfortably. |
|---|---|
| Mac | TextEdit opens plain text files. For code or data files, a free editor such as BBEdit or VS Code keeps the formatting intact. |
| iPhone and iPad | Save the file to the Files app and tap it; iOS previews most plain text. Or drop it on the viewer above, which shows the text right in the browser. |
| Android | Most file manager apps open plain text files in a built-in viewer. The viewer above also works in Chrome. |
Can you convert a .mht file?
TapToConvert does not convert MHT files. The usual route is to open the file in the program that made it and use its Export or Save as option.
MHT file FAQ
What is a .mht file?
A .mht file is an email message, with the MIME type message/rfc822.
How do I open a .mht file?
With any text editor, such as Notepad on Windows or TextEdit on a Mac, or with the viewer on this page.
Is a .mht file safe to open?
MHT files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .mht?
message/rfc822, and it is also seen as application/x-mimearchive. Web servers send this type so browsers know how to handle the file.
Is MHT a text or binary format?
Text. Its contents are readable characters.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.