YAML Validator
Validate YAML syntax instantly — free, online, and 100% private. Your YAML never leaves your browser.
The validator is built into the formatter
Paste your YAML on the home page and click Validate. Errors are highlighted inline with exact line numbers and descriptions.
Open YAML Validator →What the Validator Checks
Indentation errors
Catches misaligned keys and inconsistent indent depth.
Tab characters
YAML requires spaces. Tabs cause hard-to-spot failures.
Duplicate keys
Flags keys that appear more than once in a mapping.
Invalid scalars
Detects unclosed quotes and invalid escape sequences.
Broken anchors
Catches aliases that reference undefined anchors.
Multi-document syntax
Validates --- and ... document separators.
Type coercion traps
Warns about strings that may be parsed as booleans or numbers.
Unicode issues
Detects invalid byte sequences and encoding problems.
Common YAML Errors & Fixes
Invalid
user:
name: Alice
age: 30Valid
user:
name: Alice
age: 30All keys under a mapping must be at the same indentation level.
Invalid
config:
host: localhostValid
config:
host: localhostYAML does not allow tabs for indentation. Use 2 or 4 spaces.
Invalid
name: Alice
name: BobValid
first_name: Alice
last_name: BobDuplicate keys are technically allowed but produce undefined behavior. Most parsers warn or error.
Invalid
status: yesValid
status: "yes"In YAML 1.1, "yes", "no", "on", "off" parse as booleans. Quote them to keep them as strings.
Invalid
url: https://example.comValid
url: "https://example.com"A colon followed by a space starts a new mapping. Wrap URLs and similar values in quotes.
Frequently Asked Questions
What does the YAML validator check?
The validator checks for syntax errors including indentation mistakes, duplicate keys, invalid escape sequences, unclosed quotes, and malformed multi-document files separated by ---.
Is my YAML data sent to a server?
No. All validation runs entirely in your browser using JavaScript. Your YAML is never transmitted to any server. No data is collected, logged, or stored.
Can I validate Kubernetes YAML?
Yes. The validator supports any YAML file including Kubernetes manifests (Deployments, Services, ConfigMaps, Ingress), Docker Compose files, GitHub Actions workflows, Ansible playbooks, and Helm chart values.
What YAML version is supported?
The validator supports YAML 1.2, the current standard. YAML 1.2 is compatible with Kubernetes, Docker, and most modern DevOps tooling. It also handles common YAML 1.1 files.
Why does valid YAML still fail validation?
The most common cause is tabs instead of spaces, or inconsistent indentation. Copy your YAML into the formatter and check the error message — it will include the exact line number and a description of the problem.
Use Cases
- ✓Debug Kubernetes manifests before applying with kubectl
- ✓Validate Docker Compose files before docker-compose up
- ✓Check GitHub Actions workflows before committing
- ✓Verify Ansible playbooks and inventory files
- ✓Validate Helm chart values.yaml files
- ✓Review CI/CD pipeline configuration (CircleCI, GitLab CI, Bitbucket Pipelines)
- ✓Check OpenAPI / Swagger YAML specifications
Ready to Validate?
Paste your YAML into the editor and get instant feedback with line-by-line error highlighting.
Validate My YAML