What Is a .u8msg File? .u8msg Format, MIME & How to Open

Quick facts

Extension.u8msg

File typeU8MSG Other

MIME typemessage/global

CategoryOther

Charset—

Compressible—

What is .u8msg

What is a .u8msg file?

A .u8msg file is a U8MSG Other. It is a file format typically read and written by specialized applications.

In the mime-db registry it maps to message/global. When serving .u8msg over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to message/global — and is delivered over HTTP via the Content-Type header.

How to open .u8msg files

Use VS Code or xxd to open and edit .u8msg files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: message/global

Common software that reads/writes .u8msg:

VS Codexxd7-Zip

Relation chain

.u8msgextension of

format

U8MSG Otherserved as

mime type

message/globalsent via header

http header

Related extensions

Related MIME types

Common uses

Application-specific data

How to edit .u8msg files

Open the file with VS Code, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .u8msg files

Create a new file and save it with the .u8msg extension, or export this format from VS Code.

Frequently asked questions

What programs can open .u8msg files?

Common options include VS Code, xxd, 7-Zip. You can also open many of these files with built-in viewers or a browser.

How do I create a .u8msg file?

Create a new file in any text editor or the app that owns the format and save it with the .u8msg extension.

What is the relationship between .u8msg and the message/global MIME type?

message/global is the media type identifier used for .u8msg files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-09-13

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