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

Quick facts

Extension.cjs

File typeCommonJS Script

MIME typeapplication/node

CategoryData & Text

Charset—

Compressible—

Format familyjavascript

What is .cjs

What is a .cjs file?

A .cjs file is a CommonJS Script — CommonJS module JavaScript file for Node.js.

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

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

How to open .cjs files

Use VS Code or Node.js to open and edit .cjs 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/node

Common software that reads/writes .cjs:

VS CodeNode.js

Relation chain

.cjsextension of

format

javascriptserved as

mime type

application/nodesent via header

http header

Related extensions

Related MIME types

Related programming languages

JavaScript

.js ._js .bones

Common uses

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

How to edit .cjs 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 .cjs files

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

Frequently asked questions

What programs can open .cjs files?

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

How do I create a .cjs file?

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

What is the relationship between .cjs and the application/node MIME type?

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

Sources & standards

Updated 2026-08-18

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