// Valid YAML
name: Acme
version: 1.4.2
active: trueYAML Validator
Check YAML syntax and surface exact line and column for any error.
YAML input
Status
Why validate YAML?
YAML is whitespace-sensitive, which means a missing space or a tab character can silently break your entire configuration. Validating YAML before deploying ensures your Kubernetes manifests, Docker Compose files, CI/CD pipelines, and application settings parse correctly. A single indentation error can cause a deployment to fail or, worse, apply incorrect configuration to production systems.
This validator uses the js-yaml parser to check your YAML syntax in real time. It reports the exact line and column where the error occurred, along with a hint describing the most likely cause. You can paste any YAML document — from a simple key-value pair to a complex multi-document Kubernetes manifest — and get instant feedback without uploading your data to any server.
Common YAML syntax errors.
Tab characters. YAML forbids tabs for indentation. Use spaces consistently — typically 2 spaces per level. If your editor inserts tabs, configure it to use spaces for YAML files.
Bad indentation. Mixing indentation levels within the same document causes parse errors. Every nested level must be indented by the same amount relative to its parent. The validator pinpoints exactly which line has inconsistent indentation.
Missing colons. Every key in a YAML mapping must be followed by a colon and a value. Forgetting the colon or placing it on the wrong line is a common mistake that this validator catches immediately.
Duplicate keys. While some parsers silently accept duplicate keys (last one wins), this can hide configuration bugs. Validating helps you spot unintentional overrides before they cause problems.
How to validate YAML in your workflow.
Before committing. Run your YAML files through this validator before committing to version control. This catches syntax errors early and prevents broken configurations from reaching your CI/CD pipeline.
In CI/CD pipelines. Integrate YAML validation into your build process using yamllint or this tool's logic. Automated validation prevents invalid configurations from being applied to Kubernetes clusters or deployed to production environments.
For Kubernetes manifests. Kubernetes is particularly sensitive to YAML errors. A malformed manifest can causekubectl apply to fail silently or apply unintended changes. Always validate your manifests before applying them to a cluster.
YAML validation best practices.
Configure your editor to validate YAML on save. Most modern editors (VS Code, IntelliJ, Sublime Text) have extensions that highlight YAML errors in real time as you type. This catches issues at the earliest possible stage, before you even think about deploying. Pair the linter with a consistent indentation rule — typically 2 spaces — to eliminate the most common class of YAML errors entirely.
For team projects, add YAML linting to your pre-commit hooks and CI pipeline. A simple script that runs a YAML parser over every .yaml and .yml file in your repository prevents broken configs from being committed. Tools like yamllint offer configurable rules beyond basic syntax, including line length limits, truthy value checks, and document start markers.
When working with complex YAML structures like Kubernetes manifests or Helm charts, validate both syntax and schema. Syntax validation catches structural errors; schema validation ensures every required field is present and values match expected types. This two-step approach prevents both parse failures and runtime errors caused by missing or malformed configuration values.
Your input is processed locally and isn't uploaded for processing. Verify by opening DevTools → Network — there are no requests carrying your data.
YAML Validator examples.
// Invalid: mixed indentation
user:
name: John
age: 25// Invalid: tab character
key: valueFrequently asked questions.
What is the best YAML validator?
This online YAML validator is free, runs entirely in your browser, and provides instant line-by-line error reporting with hints. For CLI workflows, yamllint is popular. For IDE integration, VS Code extensions like "YAML" by Red Hat offer built-in validation.
What is the best Kubernetes YAML validator?
For Kubernetes manifests, use kubectl dry-run (kubectl apply --dry-run=client -f file.yaml), kubeval, or kube-linter. This online validator checks basic YAML syntax before you apply to your cluster.
How to validate YAML for Kubernetes?
Paste your manifest here for syntax validation. Then use kubectl apply --dry-run=client -f file.yaml to check against the cluster schema. Tools like kubeval and conftest validate against Kubernetes resource schemas.
How to validate YAML in VS Code?
Install the "YAML" extension by Red Hat for real-time validation. You can also paste your YAML into this online validator for a quick syntax check with detailed error locations.
What is a YAML validator used for?
A YAML validator checks syntax errors like wrong indentation, tab characters, missing colons, and duplicate keys. It helps catch issues before deploying configs to Kubernetes, Docker Compose, CI/CD pipelines, or application settings.
How to validate YAML in Python?
Use PyYAML: import yaml; yaml.safe_load(open("file.yaml")). It raises a YAMLError with line/column info on invalid syntax. For schema validation, use jsonschema with a YAML-to-JSON pipeline.
How to validate YAML in the command line?
Use yamllint: yamllint file.yaml. For Kubernetes: kubectl apply --dry-run=client -f file.yaml. Python: python -c "import yaml; yaml.safe_load(open('file.yaml'))". All provide syntax validation.
Is my YAML data uploaded?
No. Validation runs entirely in your browser using JavaScript. Your data never leaves your device — you can verify this by opening the Network tab in DevTools.
Does it check OpenAPI schema?
This validator checks YAML syntax only. For OpenAPI schema validation, use tools like swagger-cli validate or Spectral after confirming your YAML syntax is valid.
What does the error message mean?
The error points to the exact line and column where parsing failed. The hint describes the most common cause, like indentation issues, missing colons, or tab characters.