How to use the YAML Formatter
1. Paste your YAML document into the Input panel. The formatter also accepts compact or flow-style YAML (e.g., inline objects and arrays).
2. Click Format YAML — the document is parsed and re-serialized with consistent 2-space indentation and block-style collections.
3. Check the Output for validation errors. If the input is invalid YAML (e.g., inconsistent indentation, missing quotes around special characters), an error message will indicate the problem.
4. Copy the formatted YAML and use it in your configuration files, CI/CD pipeline definitions, or API payloads.
What is it?
YAML (YAML Ain't Markup Language) is a human-readable data serialization format used extensively for configuration files (Docker Compose, Kubernetes manifests, GitHub Actions, Ansible playbooks), API specifications (OpenAPI), and data exchange. Unlike JSON, YAML is indentation-sensitive — incorrect spacing causes parse errors that can break deployments.
This formatter parses your YAML using the battle-tested yaml library and re-serializes it with normalized indentation (2 spaces), explicit block-style for nested objects and arrays, and consistent string quoting. It also converts compact flow-style notation ({key: value} or [a, b, c]) to the more readable block style.
Running YAML through a formatter before committing it to version control helps prevent subtle bugs caused by invisible whitespace differences, mixed tabs and spaces, or missing quotes around strings that contain colons, hashes, or other YAML-special characters.
Example
name: my-app version: 2.0 features: [auth, api, db]
name: my-app version: 2 features: - auth - api - db
Benefits
Catch indentation errors that cause parse failures
YAML is whitespace-sensitive — formatted output shows the exact indentation structure and makes misaligned keys immediately visible.
Validate and format Kubernetes manifests in one step
Confirm your YAML is syntactically correct and properly indented before running kubectl apply or helm install.
Normalise docker-compose.yml before committing
Consistent YAML formatting prevents whitespace-related merge conflicts and makes docker-compose files readable for the entire team.
Format CI/CD pipeline YAML for readability
GitHub Actions, GitLab CI, and CircleCI YAML configs are much easier to review and debug when properly indented.
Frequently asked questions
What's the difference between YAML and JSON?
Both represent structured data, but YAML uses indentation instead of braces/brackets, supports comments (lines starting with #), and is generally more human-readable. JSON is stricter and more widely supported in APIs. YAML is a superset of JSON — all valid JSON is valid YAML.
Why does my YAML fail to parse?
Common causes are: mixing tabs and spaces (YAML only allows spaces), using a colon followed by text without a space or quotes, special characters in unquoted strings (: { } [ ] , & * # ? | - < > = ! % @ `), or inconsistent indentation levels. The error message will point to the problematic line.
Does this validate YAML as well as format it?
Yes. Because formatting requires parsing, any syntactically invalid YAML will produce an error message rather than output. This makes the formatter a quick validator as well.
Is my YAML processed on a server?
No. Parsing and formatting happen entirely in your browser. Configuration files often contain secrets, passwords, or API keys — none of that ever leaves your device.