YAML Formatter & Validator - Format & Clean YAML
Format and validate YAML files with consistent indentation. Sort keys, remove comments, and prepare clean configuration files.
YAML Code Editor
Tool Purpose & Audience
The YAML Formatter takes inconsistently-indented, messy, or difficult-to-read YAML and formats it with consistent indentation and structure — making the key-value hierarchy, lists, and nested objects immediately clear. It also validates that the YAML is syntactically correct.
DevOps engineers, backend developers, and anyone working with configuration-heavy infrastructure use this tool daily — YAML is the dominant format for Kubernetes manifests, GitHub Actions workflows, Docker Compose files, Ansible playbooks, CircleCI configs, and application configuration files.
Real-World Use Cases
- Kubernetes manifest debugging: Kubernetes YAML files define pods, deployments, services, and ingress rules. Indentation errors in Kubernetes YAML are a leading cause of deployment failures — format and validate here before applying with kubectl.
- GitHub Actions workflow editing: GitHub Actions workflows are YAML files. A single misaligned step or incorrect indentation can break a CI/CD pipeline. Format and check the structure here before committing to .github/workflows/.
- Docker Compose configuration: docker-compose.yml defines multi-container applications. Paste your compose file here to verify service definitions, volume mounts, and port mappings are correctly structured.
- Converting JSON to YAML: YAML is a superset of JSON — any valid JSON is valid YAML. Some tools let you paste JSON here for YAML-style formatting, making configuration files more readable for humans than JSON's bracket-heavy syntax.
Practical Input → Output Examples
1. Inconsistently-indented YAML
Input: YAML with mixed 2 and 4 space indentation across different sections
Output: Uniformly-indented YAML with consistent 2-space indentation throughout
Consistent indentation makes the document hierarchy immediately readable and prevents errors from indentation-sensitive YAML parsers.
2. Kubernetes deployment manifest
Input: A Kubernetes Deployment with spec.template.spec.containers nesting
Output: Formatted manifest with clear apiVersion → kind → metadata → spec hierarchy
The deep nesting of Kubernetes manifests (5–6 levels) formatted clearly — making container specs, resource limits, and env vars easy to read and edit.
3. YAML validation error
Input: YAML with a tab character used for indentation (tabs are invalid in YAML)
Output: Error — "Tabs are not allowed as indentation in YAML"
YAML strictly forbids tab characters for indentation — only spaces are allowed. This is the most common YAML parse error from developers who use tab-indenting editors without per-language settings.
Common Mistakes & Misunderstandings
Tabs are forbidden in YAML: YAML uses spaces for indentation — never tabs. If your editor inserts tabs when you press Tab in YAML files, the file will fail to parse. Configure your editor to use 2 spaces for indentation in .yml/.yaml files. This is the single most common cause of YAML syntax errors.
Indentation defines structure, not braces: Unlike JSON (which uses curly braces for objects and square brackets for arrays), YAML uses indentation level to define structure. A child key must be indented more than its parent — but all children at the same level must have identical indentation. One extra space in one key can break the entire document.
Strings don't always need quotes: YAML automatically infers types — "true", "false", "null", "1", "1.0" are interpreted as Boolean, null, and numeric types, not strings. If you want these as string values, quote them explicitly: 'true' or "false". This bites developers who use "true/false" as string config values.
Multiline strings: | vs > YAML has two multiline string styles: the literal block scalar (|) preserves newlines; the folded block scalar (>) folds newlines into spaces. Use | for shell scripts, SQL, or any content where newlines matter; use > for long prose strings where word-wrapping is fine.
How does the YAML formatter handle indentation?
You can choose spaces or tabs and set the indent size. The formatter applies consistent indentation throughout the YAML document.
Can I remove comments from YAML?
Yes. Enable the 'Remove Comments' option to strip inline comments (lines starting with #) from the output.
Does the tool validate YAML before formatting?
Yes. YAML is parsed first; if there are syntax errors, you'll see a clear error message and the process will stop.
Can I sort keys alphabetically?
Enable 'Sort Keys' to recursively sort object keys for more consistent configuration files.