YAML Validator

Validate YAML syntax with line-number error pinpointing and JSON preview.

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How to Use

Validate YAML documents instantly with line-number error pinpointing and JSON preview. This tool catches syntax errors, indentation problems, and structural issues before they break your deployments.

Paste YAML: Enter your YAML configuration, Kubernetes manifest, Docker Compose file, or any YAML document into the input panel.
Review validation: The status banner immediately shows whether your YAML is valid (green) or contains errors (red). Errors display exact line and column numbers.
Apply quick fixes: If the tool detects tab characters (which YAML forbids), click the quick fix button to automatically convert them to spaces.
Preview JSON: For valid YAML, toggle the JSON preview to see the parsed data structure. Copy the JSON output for use in applications that require JSON format.

About This Tool

YAML Syntax Rules

YAML (YAML Ain't Markup Language) is a human-readable data serialization format widely used for configuration files, infrastructure-as-code manifests, and data exchange. Unlike JSON, YAML relies on indentation to define structure rather than braces and brackets. The YAML 1.2 specification enforces strict rules: indentation must use spaces (never tabs), mapping keys require a colon followed by a space, and sequences use a dash followed by a space. This tool parses your input against these rules and reports violations with exact locations.

Common YAML Pitfalls

The most frequent YAML errors fall into four categories. First, tab characters — YAML strictly forbids tabs for indentation, but many editors default to tabs. Second, inconsistent indentation — mixing 2-space and 4-space indentation within the same document causes ambiguous parsing. Third, unquoted special values — strings like yes, no, on, off, null, and true are interpreted as boolean or null types unless explicitly quoted. Fourth, missing spaces after colons — key:value is treated as a single string, not a key-value pair. This validator catches all four categories and reports the exact location.

YAML in Modern DevOps

YAML has become the de facto standard for DevOps configuration. Kubernetes manifests, Docker Compose files, GitHub Actions workflows, Ansible playbooks, Helm charts, and CI/CD pipelines all use YAML. A single indentation error in a Kubernetes deployment manifest can prevent pods from starting. This validator helps catch these errors before kubectl apply fails in production. The JSON preview output is particularly useful when debugging — it shows exactly how YAML's implicit typing and indentation-based nesting translate to structured data.

Why Use This Tool

Private, Instant Validation

YAML configuration files frequently contain sensitive data — database credentials, API keys, infrastructure secrets, and private registry URLs. This tool validates your YAML entirely in your browser using the js-yaml library. No data is ever transmitted to any server, making it safe for production Kubernetes secrets, CI/CD pipeline variables, and internal infrastructure manifests.

The instant JSON preview bridges the gap between YAML's human-friendly syntax and JSON's machine-readable format. When debugging issues with YAML anchors, aliases, or implicit type coercion, seeing the JSON equivalent reveals exactly how your data will be interpreted by parsers and applications.

FAQ

What YAML syntax errors does this tool catch?

This tool catches all YAML 1.2 syntax errors including incorrect indentation, tab characters (forbidden in YAML), missing colons after mapping keys, unclosed quotes, duplicate keys, and malformed sequences. Error messages include exact line and column numbers for fast debugging.

What is the difference between YAML and JSON?

YAML is a human-readable superset of JSON that uses indentation instead of braces and brackets. YAML supports comments, multi-line strings, anchors, and aliases. Every valid JSON document is also valid YAML, but YAML offers additional features that make configuration files easier to read and maintain.

Can this tool convert valid YAML to JSON?

Yes. When your YAML passes validation, the tool automatically generates the equivalent JSON representation. You can toggle the JSON preview panel to inspect the parsed structure and copy the JSON output for use in applications that require JSON format.

Does the auto-fix feature modify my YAML?

The auto-fix only addresses one common issue: replacing tab characters with spaces. YAML strictly forbids tabs for indentation, and this is by far the most common error when pasting YAML from editors configured with tab indentation. All other fixes are shown as suggestions — your original input is never silently modified.