YAML Validator

YAML Input

Validation Result

What Is a YAML Validator?

YAML (YAML Ain't Markup Language) is used for config files in Kubernetes, Docker Compose, GitHub Actions, and many other tools. Unlike JSON, YAML uses indentation for structure—no brackets required. That makes it readable, but also fragile: wrong spaces, tabs instead of spaces, or inconsistent nesting cause parse errors. The YAML 1.2 specification defines the rules.

A YAML validator checks whether your document is valid. It parses your YAML and reports any syntax errors with line and position. This tool runs entirely in your browser. Nothing is sent to a server, so it's safe to use with production configs, secrets, or sensitive data.

YAML Validation Examples

Valid YAML uses consistent indentation. Invalid YAML often has wrong nesting. Telecom-themed examples:

Example 1: Valid YAML

Valid

Example 2: Invalid YAML (wrong indentation)

Invalid

The validator reports the error. Use Valid Sample or Invalid Sample above to load examples into the editor.

How to Use This Tool

Paste or Upload YAML

Copy your YAML and paste it into the left editor. You can also click Upload to load a .yaml or .yml file from your computer. Use Valid Sample for correct YAML, or Invalid Sample to see what errors look like.

Check the Validation Result

The right panel shows Valid or Invalid. If invalid, it lists errors with line and position so you can pinpoint the problem. Common issues include wrong indentation, tabs instead of spaces, inconsistent nesting, unquoted special characters, or malformed multiline strings.

Fix and Revalidate

Fix errors in the input and revalidate. For formatting and indentation, use the YAML Formatter. For conversion to JSON or other formats, use YAML to JSON or YAML to XML.

When YAML Validation Helps

Most developers need validation when working with Kubernetes manifests, Docker Compose files, or CI/CD configs like GitHub Actions. A single extra space or tab can break deployment. Running your config through here catches syntax errors before you push.

Config files like application.yml (Spring Boot) or .gitlab-ci.yml often have deep nesting. The validator helps you find the exact line where indentation goes wrong. For converting YAML to JSON or XML, use the YAML to JSON or YAML to XML tools.

If you're editing YAML in an editor without good validation, this tool gives you instant feedback. It's also useful before sharing configs with teammates—validating first ensures everyone gets a parseable file.

Frequently Asked Questions

What makes YAML invalid?

Wrong indentation (tabs instead of spaces), inconsistent nesting, unquoted special characters like : or # in values, malformed multiline strings, or duplicate keys. The validator pinpoints the issue with line and position.

Tabs vs spaces?

YAML requires spaces for indentation. Tabs are not allowed. Mixing tabs and spaces causes errors. Use 2 or 4 spaces consistently throughout your file.

Is my data sent anywhere?

No. Validation runs entirely in your browser using JavaScript. No data is sent to any server. You can confirm this by opening your browser's Network tab while using the tool.

What about YAML anchors and aliases?

Anchors (&name) and aliases (*name) are supported. The validator checks that they are used correctly. Circular references will cause validation to fail.

Does it check schema or just syntax?

This tool validates syntax only—whether the YAML is well-formed and parseable. It does not validate against a JSON Schema or Kubernetes schema. For structure validation, convert to JSON and use the JSON Schema Generator.