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.CML·File Extension

CML Other — A .cml file is a CML Other. It is a file format typically read and written by specialized applications.

Otherchemical/x-cml

Quick facts

Extension.cml
File typeCML Other
MIME typechemical/x-cml
CategoryOther
Charset—
Compressible—

What is .cml

What is a .cml file?

A .cml file is a CML Other. It is a file format typically read and written by specialized applications.

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

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

How to open .cml files

  • Use VS Code or xxd to open and edit .cml 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: chemical/x-cml

Common software that reads/writes .cml:

VS Codexxd7-Zip

Relation chain

.cmlextension of
format
CML Otherserved as
mime type
chemical/x-cmlsent via header
http header
Content-Type

Related extensions

.cdx
CDX Other
.cif
CIF Other
.cmdf
CMDF Other
.csml
CSML Other

Related MIME types

chemical/x-cml
.cml

Common uses

  • Application-specific data

How to edit .cml 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 .cml files

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

Frequently asked questions

What programs can open .cml 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 .cml file?

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

What is the relationship between .cml and the chemical/x-cml MIME type?

chemical/x-cml is the media type identifier used for .cml files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-09-13

Explore this reference

Related extensions

.cdx
CDX Other
.cif
CIF Other
.cmdf
CMDF Other
.csml
CSML Other

Related MIME types

chemical/x-cml
.cml

Related headers

Content-Type
HTTP header
Accept
HTTP header

Related methods

GET
HTTP method
POST
HTTP method
PUT
HTTP method
PATCH
HTTP method

Related status codes

200
OK
404
Not Found

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