Tools
YAML Formatter
The YAML formatter parses and reformats YAML documents with normalized indentation and syntax highlighting. It detects syntax errors including indentation inconsistencies, duplicate keys, and invalid scalar values, and reports them with line numbers. The tool is useful for developers working with Kubernetes manifests, Docker Compose files, CI/CD pipeline configurations, and any other YAML-based infrastructure-as-code.
What is the YAML Formatter?
The YAML formatter is a browser-based tool that validates and normalizes YAML documents. YAML is whitespace-sensitive, making it prone to errors that are invisible to the naked eye — a single misaligned space can change the document structure or cause a parse failure. The formatter parses the YAML, catches errors with precise location information, and re-serializes the document with consistent 2-space indentation. It handles all YAML 1.2 features including anchors, aliases, multi-line scalars, and explicit type tags.
How does it work?
Paste your YAML into the input area and click Format. The tool parses the document using a JavaScript YAML parser and reports any syntax errors. On success, it serializes the parsed data back to YAML with normalized indentation and quoting. You can also convert the YAML to JSON to verify that the parsed data structure matches your expectation. The formatted output is syntax-highlighted with different colors for keys, values, scalars, and comments.
Typical Use Cases
- Validating a Kubernetes YAML manifest before applying it to a cluster
- Normalizing indentation in a Docker Compose file that mixes tabs and spaces
- Debugging a GitHub Actions workflow that fails with a cryptic parse error
- Cleaning up Ansible playbooks before committing to version control
Step-by-step Guide
- Step 1: Paste your YAML content into the input field.
- Step 2: Click Format to validate and normalize the document.
- Step 3: Review any syntax errors reported with line and column numbers.
- Step 4: Copy the formatted YAML for use in your configuration files.
Example
Input
name: Alice age: 30 roles: - admin - user
Output
name: Alice age: 30 roles: - admin - user
Tips & Notes
- Never mix tabs and spaces in YAML — use spaces only. Most editors can be configured to insert spaces on Tab key press.
- Use quotes around strings that contain special characters like :, #, or leading/trailing spaces.
- Anchors (&) and aliases (*) can reduce repetition in large YAML files but make them harder to read — use sparingly.
Frequently Asked Questions
Why does YAML parse a bare 'yes' or 'no' as a boolean?
YAML 1.1 treats yes, no, on, off, true, and false as booleans. YAML 1.2 restricts this to only true and false. Quote the value ('yes') to force it to be treated as a string regardless of parser version.
What is the difference between block style and flow style YAML?
Block style uses indentation to define structure and is the human-readable default. Flow style uses JSON-like braces and brackets ({key: value}, [a, b]). Both are valid YAML and can be mixed in the same document.
YAML Formatter
Format and prettify YAML documents with syntax highlighting, line numbers, indentation correction, and structure statistics.
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