YAML Formatter & Validator

Example Input

name: John Doe
age: 30
city: New York
hobbies:
  - reading
  - coding
  - hiking
isDeveloper: true
address:
  street: 123 Main St
  zip: 10001

Example Output

Validation Result: Valid YAML

name: John Doe
age: 30
city: New York
hobbies:
  - reading
  - coding
  - hiking
isDeveloper: true
address:
  street: 123 Main St
  zip: 10001

No errors found. Structure: 1 document, 6 top-level keys, 1 nested mapping (address), 1 sequence (hobbies).

Can it convert YAML to JSON?

This tool focuses on YAML formatting and validation rather than YAML-to-JSON conversion. Many developers use it to validate YAML before converting to JSON with other tools. If you need to convert YAML to JSON, the most reliable approach is using a library in your language of choice: js-yaml in JavaScript with yaml.load() then JSON.stringify(), PyYAML in Python with yaml.safe_load() then json.dumps(), or the yq command-line tool which supports both YAML and JSON transformations. These programmatic approaches handle edge cases like YAML anchors and multi-document files more reliably than browser-based converters.

Does it support multi-document YAML?

Yes. Multi-document YAML files — where multiple YAML documents are separated by the --- document separator — are fully supported. This is common in Kubernetes manifest files that define multiple resources (Deployment, Service, ConfigMap) in a single file. The tool validates and formats each document independently, reports errors with document context so you know which document in the file has the issue, and outputs the formatted result with the --- separators preserved.

Is it safe for secrets and sensitive config?

Yes. All formatting and validation runs entirely in your browser using a JavaScript YAML parser. Your YAML content — including Kubernetes secrets, Docker registry credentials, API keys, database connection strings, and TLS certificates — never leaves your machine. Browser-based processing means there is no server that could log your config values, no network transmission that could intercept sensitive data, and no third-party storage of your infrastructure configuration.

What is the difference between YAML 1.1 and YAML 1.2?

YAML 1.2 was released in 2009 and clarified several ambiguities from YAML 1.1, most importantly the boolean synonym issue. In YAML 1.1, the values yes, no, on, off, and their case variations are treated as booleans — this caused the famous Norway Problem where the country code NO was parsed as boolean false. YAML 1.2 restricts boolean values to only true and false, eliminating this confusion. However, many widely-used YAML parsers — including PyYAML before version 6.0 and many Kubernetes-related tools — still implement YAML 1.1 behavior. Always quote string values that look like booleans regardless of which YAML version your tool claims to use.

Why does my YAML validate here but fail in Kubernetes?

This tool validates YAML syntax — whether the document is structurally valid YAML. Kubernetes adds an additional layer of validation on top of YAML syntax: it checks whether the resource structure, field names, and values conform to the Kubernetes API schema for that resource type. A YAML file can be perfectly valid YAML but fail Kubernetes validation because a required field is missing, a field name is misspelled (containers instead of container for example), an unsupported field is included, or a value is the wrong type for that field. For Kubernetes-specific validation, use kubectl apply --dry-run=client or kubectl apply --dry-run=server after validating the YAML syntax here.

How do I fix indentation errors in a large YAML file?

Paste the entire file into this tool and click Format YAML. If the YAML is structurally valid despite inconsistent indentation, the formatter will normalize it to consistent two-space indentation throughout. If there are actual syntax errors, the validator reports each one with a line number — fix them starting from the first reported error, since YAML errors often cascade and fixing the first error resolves several subsequent ones. For very large files, a good strategy is to validate section by section — paste each major block separately to isolate which part of the file contains the error.

Does it work with Kubernetes manifests, Docker Compose, and GitHub Actions?

Yes. All three use standard YAML and validate correctly with this tool. Kubernetes manifests validate for YAML syntax — for Kubernetes-specific field validation use kubectl --dry-run. Docker Compose files validate for YAML syntax and formatting. GitHub Actions workflow files validate for YAML syntax — for Actions-specific validation the actionlint tool checks action-specific rules like valid event triggers and proper uses syntax. This tool is your first gate for YAML syntax before using the tool-specific validators.

What does the --- separator mean in YAML files?

The three dashes --- mark the start of a new YAML document within a file. A single YAML file can contain multiple independent documents separated by ---. In Kubernetes, this is used to define multiple resources in one file — a Deployment, a Service, and a ConfigMap all in one manifest.yaml file separated by --- markers. Each document is parsed independently, so an error in the second document does not affect parsing of the first. The optional ... three-dot marker ends a YAML document explicitly, though it is rarely used in practice. When you paste a multi-document file into this tool, the --- separators are preserved in the formatted output.