YAML Formatter & Validator
Paste your YAML to format, validate, and minify it instantly.
About This Tool
The YAML Formatter & Validator is a free browser-based tool that helps developers quickly format, validate, and minify YAML data. YAML (YAML Ain't Markup Language) is a human-readable data serialization format widely used for configuration files in tools like Kubernetes, Docker Compose, Ansible, GitHub Actions, and many CI/CD pipelines. Getting the indentation and structure right is critical since YAML relies on whitespace for nesting.
All processing happens entirely in your browser. Your data never leaves your machine — there are no server round-trips, no logging, and no third-party analytics on your input. This makes it safe for sensitive configuration files containing secrets, credentials, and internal infrastructure details.
The formatter supports customizable indentation with 2-space or 4-space options. You can switch between block style (the standard human-readable format) and flow style (a compact, JSON-like inline representation) for minification. This is especially useful when you need to embed YAML in other formats or reduce file size for transfer.
When your YAML contains syntax errors, the tool provides detailed error messages with line and column numbers so you can quickly locate and fix issues. Common problems like incorrect indentation, missing colons, duplicate keys, and invalid special characters are all caught and reported clearly. The file size comparison feature shows you exactly how much your YAML grew or shrank after formatting or minification, displayed as both absolute bytes and a percentage change.
Whether you are debugging a Kubernetes manifest, cleaning up an Ansible playbook, or validating a CI configuration file, this tool gives you instant feedback without installing any software or creating an account.
How to Use
- Paste or type your YAML into the Input YAML panel on the left.
- The formatted output appears automatically in the Output panel on the right.
- Use the Format button for beautified block-style output, or Minify for compact flow-style output.
- In Format mode, toggle between 2-space and 4-space indentation using the badges.
- Click Sample to load example YAML (a Kubernetes Deployment manifest) to see the tool in action.
- Click Copy to copy the output to your clipboard, or Clear to reset both panels.
- If your YAML has syntax errors, an error message with line and column numbers is displayed above the panels.
- Use the keyboard shortcut Ctrl+Shift+C to quickly copy the output.
Popular YAML Formatting Examples
FAQ
Is my data safe when using this tool?
Yes. All YAML parsing and formatting is performed client-side in your browser using JavaScript. No data is transmitted to any server. You can safely use this tool with configuration files that contain secrets, API keys, or other sensitive values.
What YAML features are supported?
The tool supports all standard YAML 1.2 features including nested mappings and sequences, multi-line strings (literal and folded block scalars), anchors and aliases, comments, tags, and multi-document files. Both block style and flow style are supported for formatting output.
What happens when my YAML has syntax errors?
An error message is displayed with the line number and column where the parser encountered the problem, along with a description of the issue. This helps you quickly locate and fix indentation mistakes, missing colons, or other syntax problems.
What is the difference between Format and Minify?
Format outputs YAML in block style with proper indentation, making it easy to read and edit. Minify outputs YAML in flow style, which uses curly braces and square brackets similar to JSON. Flow style is more compact and can reduce file size, but is harder to read for complex structures.
Can I use this for Kubernetes YAML files?
Absolutely. This tool is perfect for formatting and validating Kubernetes manifests including Deployments, Services, ConfigMaps, Secrets, and Helm chart values files. The sample button loads a Kubernetes Deployment example so you can try it immediately.
Does the tool preserve YAML comments?
YAML comments are stripped during parsing and are not preserved in the formatted output. This is a limitation of most YAML processors. If you need to keep comments, consider using the tool only for validation (to check syntax) and manually formatting the file.
What does the file size comparison show?
Below each panel, the tool displays the byte size of the input and output. The output also shows a percentage indicating how much the size changed after formatting or minification. A negative percentage (shown in green) means the output is smaller, while a positive percentage (shown in yellow) means it grew.
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