What is a .yaml file? (YAML)

YAML is a human-friendly data format built for configuration. It uses indentation instead of brackets, so it reads cleanly, which is why tools like Docker, Kubernetes and countless CI systems use YAML for their settings.

What is a .yaml file used for?

YAML expresses the same data as JSON but with far less punctuation, relying on indentation to show structure. That makes config files easy to read and edit by hand.

It has become the default for DevOps and app configuration, appearing in Docker Compose, Kubernetes, GitHub Actions and many frameworks.

Its reliance on exact indentation is also its trap: one stray space can change the meaning, so a linter is your friend.

How to open a .yaml file

The .yaml format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .yaml file.

Windows

VS Code
Notepad++
any editor

macOS

VS Code
any editor

Linux

VS Code
nano
any editor

Web

Online YAML validators

How to convert a .yaml file

You can convert a .yaml file to JSON, XML using a conversion tool or the export menu of an app that opens it.

.yaml file signature (magic bytes)

Programs recognise a .yaml file by the bytes at the start of the file, not by its name. These are the signatures for YAML.

Hex signature	Offset	Note
(no fixed signature)	0	no fixed signature; indentation-based text

See the full magic-numbers reference for every format.

Frequently asked questions

What is a .yaml file?

Why is my YAML file failing to parse?

YAML is indentation-sensitive and forbids tabs for indentation. A single misplaced space or a tab character is the usual cause. Run it through a linter.

Related formats

Sources

Details on this page were checked against authoritative references:

Wikipedia: YAML