YAML Validator
Validate YAML online and find indentation, syntax and structure problems before using configuration files in applications, deployments or development workflows.
Paste YAML in the left pane and click "Validate YAML" to check syntax.
How to Validate YAML Online
Identify indentation and structural errors in your YAML configs in four straightforward steps:
Paste YAML Content
Paste your YAML file, Kubernetes manifest, or CI/CD workflow into the left editor pane or test using our samples.
Execute Validation
Click "Validate YAML" to parse mappings, list sequences, and scalars against official YAML 1.2 syntax rules.
Inspect Diagnostics
Valid configurations display structural mapping counts, while invalid files provide clear error diagnostics.
Fix Indentation
Correct spacing discrepancies, remove illegal tab characters, and verify your file before deploying to production.
What is a YAML Validator?
A YAML Validator (or YAML Syntax Checker) is a developer utility that parses YAML documents to detect syntax violations, invalid indentation levels, forbidden characters, and malformed data structures.
Because YAML relies strictly on whitespace indentation to define data hierarchy rather than explicit brackets or tag delimiters, even a single accidental space or tab character can silently change an object into a scalar or cause automated deployments to fail catastrophically.
CodeCrate's browser-based validator tests your document structure in real time, alerting you to syntax errors before you commit configuration files to Git repositories or trigger automated CI/CD deployments.
YAML Syntax Error Example: Valid vs Invalid
A missing space or bad indentation will cause YAML parsers to fail. Compare common syntax errors:
server:
host:0.0.0.0
port: 8080
services:
- web
- apiserver:
host: 0.0.0.0
port: 8080
services:
- web
- apiKey Features of CodeCrate YAML Validator
Built for reliable pre-flight configuration validation in DevOps pipelines:
Immediate Error Diagnostics
Provides actionable error descriptions indicating precisely why the YAML parser rejected the document.
Zero Data Transmission
Executed entirely in browser memory. Sensitive production environment variables, tokens, and cluster URLs are safe.
Detailed Structure Inspection
Reports high-level document metrics including root mapping type, key counts, and line numbers upon successful validation.
Common Developer Use Cases
Typical workflows where developers validate YAML documents:
1. Kubernetes Pre-Flight Checks
Check manifests before running kubectl apply to avoid deployment rollbacks caused by simple syntax mistakes.
2. GitHub Actions Workflow Audits
Verify .github/workflows/*.yml files locally before committing to prevent failed CI build triggers.
3. Docker Compose Validation
Ensure volume mounts, environment variables, and network configurations are structured properly in Compose files.
4. Ansible Playbook Testing
Validate YAML syntax in automated server provisioning playbooks before executing automated cloud tasks.
Common YAML Pitfalls & Indentation Rules
Watch out for these frequent mistakes when writing or editing YAML configuration files:
- No Tabs Allowed: Indentation must consist exclusively of spaces. A single tab will cause an instant parsing error in all standard YAML parsers.
- Space After Colon: A key-value pair requires a space after the colon (
key: value). Without the space, it is parsed as a single literal string. - Quoting Special Strings: Values containing colons (like URLs), asterisks, or leading symbols should be wrapped in quotation marks.
Frequently Asked Questions
Answers to common questions regarding YAML syntax errors, schemas, and privacy.
What does this YAML Validator check?
The validator tests YAML syntax against official YAML specifications, identifying incorrect indentation, improper colon spacing, tabs used in place of spaces, and malformed mappings.
Does this tool validate against Kubernetes or Docker schemas?
No. This tool validates YAML grammatical syntax and structure. It does not enforce custom domain-specific API schemas like Kubernetes CRDs or Docker Compose specifications.
Why does YAML fail when using tab characters?
The official YAML 1.2 specification forbids tabs because different text editors render tabs with varying column widths, which would lead to ambiguous block hierarchy interpretations.
Is my YAML configuration secure when validating?
Yes. All validation is processed 100% locally in your web browser. Sensitive cloud credentials, database connection strings, and infrastructure tokens are never transmitted to any server.
Can I test an error sample to see how errors are reported?
Yes. Click 'Error Sample' on the toolbar to test an invalid YAML snippet and observe how the validator pinpoints indentation discrepancies.
Does this validator support comments and document markers?
Yes. Standard YAML comments (# ...) and document boundary markers ('---' and '...') are fully recognized and parsed accurately.
Related Developer Tools
Explore companion YAML and data validation utilities in the CodeCrate suite: