The YAML Validator checks whether your YAML document has valid syntax by parsing it with the js-yaml library. YAML is widely used for configuration files in Docker, Kubernetes, CI/CD pipelines, and application settings, but its indentation-sensitive syntax makes it easy to introduce errors. This tool instantly identifies syntax problems and provides descriptive error messages with line numbers, helping you catch issues before deploying configurations. Paste your YAML, click Validate, and get immediate feedback. All validation runs entirely in your browser — your configuration data is never sent to a server, ensuring complete privacy for sensitive infrastructure files.
About YAML Validator
YAML (YAML Ain't Markup Language) is a human-readable data serialization format that uses indentation to define structure. While its readability is an advantage, the reliance on indentation makes YAML prone to subtle syntax errors — a single misplaced space or tab can break an entire configuration file.
This validator uses the js-yaml library to parse your YAML input and reports any syntax errors with descriptive messages and line numbers. It checks for common issues like incorrect indentation, missing colons, unquoted special characters, and invalid data types. Note that this tool validates YAML syntax only — it does not check against application-specific schemas. Since all parsing runs in JavaScript within your browser, your configuration data remains private and is never transmitted.
How to Use YAML Validator
- Paste or type your YAML into the input area.
- Click Validate YAML to check the syntax.
- If the YAML is valid, you will see "Valid YAML." If there are errors, a descriptive message shows the problem and line number.
- Fix any reported issues and validate again until the YAML passes.
Key Features
- Syntax validation — Catches indentation errors, missing colons, and invalid characters
- Descriptive error messages — Shows what went wrong and the line number
- Powered by js-yaml — Uses a trusted library that supports the YAML 1.2 specification
- Instant results — Validation completes immediately after clicking the button
- Client-side privacy — No data leaves your browser; safe for sensitive configs
When to Use This Tool
- Validating Docker Compose, Kubernetes, or CI/CD pipeline configurations before deployment
- Checking YAML config files for syntax errors during development
- Verifying hand-edited YAML before committing to version control
- Debugging "invalid YAML" errors from applications or build systems
- Learning YAML syntax by experimenting and getting instant error feedback
Technical Details
The validator uses the js-yaml library's jsyaml.load() function with safe schema mode to parse the input. If parsing succeeds, the YAML is confirmed as valid. If it fails, the js-yaml library throws an exception containing the error message, line number, and column number, which the tool displays to you. Common errors include: inconsistent indentation (mixing tabs and spaces), missing colon after a key, unquoted special characters (e.g., @ or *), and duplicate keys. This is a syntax validation only — it does not check against application-specific schemas or constraints. All processing runs in JavaScript within your browser.
Conclusion
YAML Validator is an essential tool for anyone working with YAML configuration files. With instant syntax checking, descriptive error messages, and complete browser-side privacy, it helps you catch and fix YAML errors before they cause deployment failures. For converting between YAML and JSON, use the YAML Converter.