Validate Your YAML Syntax Instantly Yaml Validator - a developer utility tool.
Yaml Validator
Yaml Validator - a developer utility tool.
Paste Your YAML Code
Paste or type your YAML content into the input editor.
Run the Validation
Click validate to check your YAML for syntax errors.
Review Error Details
View validation results highlighting any errors or formatting issues.
What Is Yaml Validator?
A Yaml Validator is a software tool that checks YAML code for syntax errors and formatting issues, ensuring the data is correctly formatted according to the official YAML specification. Developers working with configuration files, containerization tools like Kubernetes, or other applications that rely on YAML for data exchange use it to identify mistakes in their YAML code. One specific problem it solves is detecting indentation inconsistencies, which can be tricky to spot manually, especially in large and complex YAML documents.
This tool stands out due to its ability to not only validate the syntax but also provide detailed information about the parsed document, such as the root type of the YAML data, total number of keys, and maximum depth. It achieves this by using a library like js-yaml to parse the input string into a JavaScript object, which can then be analyzed further. For instance, it counts the keys in nested objects recursively, giving an accurate count even for deeply nested structures.
When you use it as a yaml syntax checker or online yaml validation tool, you get feedback on potential issues like incorrect indentation and suggestions to fix common problems such as using tabs instead of spaces or failing to quote values containing special characters. This makes the process of validating YAML files more efficient and helps avoid errors that could lead to parsing failures when the YAML data is used in applications, allowing for quick validation without needing to set up a local environment for yaml lint online free checks.
Why Use Yaml Validator?
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Free and open-source with no signup required
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Runs entirely in your browser — your data never leaves your device
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Fast and responsive interface for quick developer tasks
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No installation needed — works on any modern browser
Common Use Cases
Daily Development
Validate YAML configuration files during your regular development workflow.
Code Review
Helpful when reviewing pull requests that include YAML config or pipeline definitions.
Learning
Great for learning YAML syntax and experimenting with different data structures.
Team Collaboration
Share the tool with team members to maintain consistent YAML formatting standards.
Technical Guide
The Yaml Validator works by utilizing the js-yaml library to parse the input YAML string into a JavaScript object. This process involves recursively traversing the nested objects in the YAML data structure, allowing it to accurately count keys and determine the maximum depth of the document. The getTypeName function is used to identify the root type of the parsed YAML data, which can be null, Array, Date, or one of the primitive types such as string, number, boolean, etc.
When parsing the input string, js-yaml may throw a YAMLException if it encounters any syntax errors, in which case the tool catches this exception and extracts relevant information from it, including the line and column numbers where the error occurred. This information is then used to generate an error message that includes suggestions for common fixes, such as checking for tabs or inconsistent indentation levels. The countKeys function uses a recursive approach to count the keys in nested objects, handling arrays by summing up the key counts of each item.
The tool also converts the parsed JavaScript object back into a JSON string using the JSON.stringify method with an indentation level of 2 spaces, which allows it to calculate the total number of lines in the equivalent JSON representation. This conversion is done to provide additional information about the structure and complexity of the YAML data, making it easier for developers to understand and work with their configuration files or other applications that rely on YAML.
The React library is used to handle user input and render the validation results, with the TextToolLayout component providing a standard interface for text-based tools like this one. The useCallback hook from React ensures that the onProcess function is only recreated when necessary, which helps optimize performance by reducing unnecessary re-renders of the component.
The use of js-yaml as the parsing library allows it to support all the features and syntax defined in the official YAML specification, including complex data structures like nested sequences and mappings. This makes it a reliable choice for validating YAML files in a variety of contexts, from configuration files for containerization tools like Kubernetes to data exchange formats for web services or other applications that rely on YAML.
Tips & Best Practices
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1Bookmark this tool for quick access during development
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2Use keyboard shortcuts for faster workflow
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3All processing happens locally — safe for sensitive data
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4Works offline once the page is loaded
Frequently Asked Questions
Q Is this YAML validator free to use?
Q Is my YAML data safe when using this tool?
Q Does the YAML validator work on mobile?
Q Can I validate YAML files offline?
Q What browsers support the YAML validator?
About This Tool
Yaml Validator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.