YAML & Config

YAML vs YML: Is There Any Difference?

The .yaml and .yml extensions normally identify the same YAML data format. The content syntax does not change with the filename suffix.

Published Aug 24, 2026

The short answer

Both extensions identify YAML documents; they do not select separate parsers or grammars by themselves.

YAML vs YML at a glance

Feature	.yaml	.yml
Format	YAML	YAML
Syntax	Same	Same
Parser behavior	Same	Same
File extension length	4 characters	3 characters
Recommended choice	Follow tool/project convention	Follow tool/project convention
Best practice	Be consistent in one project	Be consistent in one project

Does the extension change YAML syntax?

No. A parser validates the document content. A particular framework or command may require one filename, but that is an external convention rather than a YAML syntax difference.

The same rules for comments and multiline strings apply under either extension.

Why both .yaml and .yml exist

Both conventions are established in real projects. Compatibility with an existing ecosystem and repository matters more than expanding or shortening the suffix.

Should you use .yaml or .yml?

Follow an explicit filename or extension required by the consuming tool or framework.
Match the convention already used in the repository.
For a new project, choose one extension and use it consistently for new files.
The YAML content stays the same whichever extension you choose.

Examples of identical YAML content

The body is identical under either filename. The formatter works with the pasted YAML content and does not simulate filename handling.

# config.yaml or config.yml
service:
  name: api
  port: 8080

When expanding this configuration, use YAML lists for sequences and anchors and aliases to reuse values; neither depends on the filename suffix.

Common mistakes

Assuming one extension supports features the other does not.
Renaming a required ecosystem filename without checking its convention.
Treating a filename choice as proof that the content is valid YAML.

Try the YAML content

Load the shared example in YAML Formatter to validate its structure. Content validity is independent of the extension in this workflow.

Frequently asked questions

Is YML the same as YAML?

Yes. .yml and .yaml normally identify the same YAML format and use the same syntax.

Is .yaml better than .yml?

Functionally, no. The choice depends on tooling requirements and your project's naming convention.

Can I rename a .yml file to .yaml?

Usually, yes, if the consuming tool does not require a specific filename or extension. Update any references to the old filename.

Try the example

Validate content used by .yaml and .yml

The same YAML body is valid independently of the filename extension.

service:
  name: api
  port: 8080

Expected result: Valid YAML with one service mapping.

Try the shared content

Format the YAML content

Validate the same configuration independently of its filename extension.

Open in YAML Formatter →