lookup> .xul

.XUL·File Extension

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

Data & Textapplication/vnd.mozilla.xul+xmlCompressible

Quick facts

Extension.xul

File typeXUL Data & Text

MIME typeapplication/vnd.mozilla.xul+xml

CategoryData & Text

Charset—

CompressibleYes

What is .xul

What is a .xul file?

A .xul file is a XUL 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/vnd.mozilla.xul+xml, and it is marked as compressible. When serving .xul over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to application/vnd.mozilla.xul+xml and is used by XML among others — and is delivered over HTTP via the Content-Type header.

How to open .xul files

Use VS Code or Notepad++ to open and edit .xul 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/vnd.mozilla.xul+xml

Common software that reads/writes .xul:

VS CodeNotepad++Sublime Textjq

Relation chain

.xulextension of

format

XUL Data & Textserved as

mime type

application/vnd.mozilla.xul+xmlsent via header

http header

Related extensions

Related MIME types

application/vnd.mozilla.xul+xml

.xul

Related programming languages

XML

.xml .adml .admx

Common uses

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

How to edit .xul 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 .xul files

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

Frequently asked questions

What programs can open .xul 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 .xul file?

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

What is the relationship between .xul and the application/vnd.mozilla.xul+xml MIME type?

application/vnd.mozilla.xul+xml is the media type identifier used for .xul files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-08-18

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