YAML Formatter & Validator
A professional-grade YAML formatting engine built for developers. Fix messy indentation, handle multiline strings, and validate your YAML schema against production standards instantly.
100% Private & Secure
This tool runs completely inside your browser using client-side WebAssembly and JS. Zero data is ever sent to our servers.
Expert Technical Insight: YAML vs YML
YAML (YAML Ain't Markup Language) is a human-readable data serialization standard often used for configuration files (Docker, Kubernetes, GitHub Actions). While both .yaml and .yml are identical in function, .yaml is the official recommended extension by the YAML Org.
Indentation Hardening
YAML is indentation-sensitive. Our formatter ensures a strict adherence to your chosen indent size (2 or 4 spaces) and prevents the "Tab Error" by automatically converting tab characters to valid space blocks.
Multiline String Support
We provide specific cleanup for multiline strings using the | (literal) and > (folded) operators, ensuring your long-form text remains valid across all YAML parsers.
How to use this tool
- Paste your YAML payload into the high-fidelity Monaco Editor.
- Click 'Format YAML' to apply standard indentation (2 or 4 spaces).
- Use 'Smart Fix' to automatically detect and correct tab-vs-space errors and trailing whitespaces.
- Your clean, valid YAML is ready for one-click copying to your local config.
Example Usage
api: version: v1 metadata: name: my-app
api:
version: v1
metadata:
name: my-appWhen to use this tool
- Kubernetes Config: Validating and formatting large K8s resource manifests.
- Docker Compose: Fixing indentation errors in microservice orchestrations.
- CI/CD Pipelines: Testing GitHub Actions or GitLab CI YAML syntax before pushing.
- YML vs YAML Analysis: Comparing file structures and ensuring naming consistency across projects.
Frequently Asked Questions
How to format YAML online securely?
Our tool processes 100% of your data locally in the browser. Unlike other online formatters, your sensitive configuration keys never touch a remote server.
Can I fix YAML indentation errors automatically?
Yes. Our 'Smart Fix' feature is specifically designed to handle the #1 cause of YAML failures: mismatched tabs and spaces. It normalizes indentation to your preferred setting (2 or 4 spaces).
What is the difference between .yaml and .yml?
There is no functional difference. Both extensions map to the same YAML data standard. However, official documentation prefers .yaml for consistency in large-scale projects.
Support for multiline strings?
Our formatter preserves and cleans literal (|) and folded (>) multiline blocks, ensuring your config file remains legible and valid.
Built by Developers, For Developers
DevToolsLabs is engineered by a team of full-stack developers who were tired of spammy, ad-filled, server-side tools parsing our sensitive data. Every utility on this site is rigorously tested, strictly client-side (your data never leaves your browser), and built to solve real-world software engineering challenges.