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.UBJ·File Extension

UBJ Data & Text — A .ubj file is a UBJ Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.

Data & Textapplication/ubjson

Quick facts

Extension.ubj

File typeUBJ Data & Text

MIME typeapplication/ubjson

CategoryData & Text

Charset—

CompressibleNo

What is .ubj

What is a .ubj file?

A .ubj file is a UBJ Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.

In the mime-db registry it maps to application/ubjson, and it is marked as non-compressible. When serving .ubj over HTTP, set the Content-Type header as shown in Developer info below.

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

How to open .ubj files

Use VS Code or Notepad++ to open and edit .ubj 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: application/ubjson

Common software that reads/writes .ubj:

VS CodeNotepad++Sublime Textjq

Relation chain

.ubjextension of

format

UBJ Data & Textserved as

mime type

application/ubjsonsent via header

http header

Related extensions

Related MIME types

Common uses

Configuration files
Data interchange between systems
API request and response payloads
Logs and data exports

How to edit .ubj 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 .ubj files

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

Frequently asked questions

What programs can open .ubj files?

Common options include VS Code, Notepad++, Sublime Text. You can also open many of these files with built-in viewers or a browser.

How do I create a .ubj file?

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

What is the relationship between .ubj and the application/ubjson MIME type?

application/ubjson is the media type identifier used for .ubj files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-09-13

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