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

Quick facts

Extension.cil

File typeCIL Document

MIME typeapplication/vnd.ms-artgalry

CategoryDocument

Charset—

Compressible—

What is .cil

What is a .cil file?

A .cil file is a CIL Document. It is a document format used for word processing, spreadsheets, presentations or ebooks.

In the mime-db registry it maps to application/vnd.ms-artgalry. When serving .cil over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to application/vnd.ms-artgalry and is used by CIL among others — and is delivered over HTTP via the Content-Type header.

How to open .cil files

Use Microsoft 365 or LibreOffice to open and edit .cil 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.ms-artgalry

Common software that reads/writes .cil:

Microsoft 365LibreOfficeAdobe AcrobatGoogle Docs

Relation chain

.cilextension of

format

CIL Documentserved as

mime type

application/vnd.ms-artgalrysent via header

http header

Related extensions

Related MIME types

application/vnd.ms-artgalry

.cil

Related programming languages

CIL

.cil

Common uses

Reports and letters
Spreadsheets and budgets
Presentations
Ebooks

How to edit .cil files

Open the file with Microsoft 365, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .cil files

Create a new file and save it with the .cil extension, or export this format from Microsoft 365.

Frequently asked questions

What programs can open .cil files?

Common options include Microsoft 365, LibreOffice, Adobe Acrobat. You can also open many of these files with built-in viewers or a browser.

How do I create a .cil file?

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

What is the relationship between .cil and the application/vnd.ms-artgalry MIME type?

application/vnd.ms-artgalry is the media type identifier used for .cil files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-08-18

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