What is YAML?
YAML (YAML Ain't Markup Language) is a human-friendly data serialization language commonly used for writing configuration files. Unlike JSON, YAML uses indentation to represent hierarchy, supports comments, and offers a cleaner syntax for complex data structures. YAML is a strict superset of JSON, meaning any valid JSON document is also valid YAML.
YAML was first proposed in 2001 and has become the de facto standard for configuration in DevOps tools, CI/CD pipelines, container orchestration, and infrastructure as code. Its emphasis on readability makes it ideal for files that humans frequently edit, while JSON remains preferred for data interchange between systems and APIs.
YAML vs JSON Comparison
| Feature | YAML | JSON |
|---|---|---|
| Readability | Very readable, minimal syntax | More verbose with braces and quotes |
| Comments | Supported with # | Not supported |
| Data types | Strings, numbers, booleans, null, dates, binary | Strings, numbers, booleans, null |
| Syntax | Indentation-based | Braces and brackets |
| File size | Typically smaller | Larger due to delimiters |
| Parsing speed | Slower (complex grammar) | Faster (simpler grammar) |
| Multi-line strings | Native support (| and >) | Requires escape sequences |
| Primary use | Configuration files | API data interchange |
YAML Syntax Reference
Key-value pairs
Use colon and space: key: value. Keys don’t need quotes unless they contain special characters.
Nested objects
Indent child keys by 2 spaces. Each level of nesting adds another 2 spaces of indentation.
Arrays (sequences)
Use a dash and space: - item. Each item on its own line at the same indentation level.
Strings
Plain (unquoted), 'single-quoted', or "double-quoted". Double quotes support escape sequences like \n.
Multi-line strings
| (literal) preserves newlines. > (folded) joins lines with spaces. Both are followed by an indented block.
Comments
Start with # and continue to end of line. Can be on their own line or inline after a value.
Booleans
true/false, yes/no, True/False, Yes/No, TRUE/FALSE, YES/NO are all valid boolean values.
Null values
Use ~ or null or simply leave the value empty after the colon.
Common YAML Use Cases
Docker Compose
Define multi-container applications with services, networks, volumes, and environment variables in docker-compose.yml.
Kubernetes
Declare pods, deployments, services, and ingress rules. K8s manifests are almost exclusively YAML.
CI/CD Pipelines
GitHub Actions, GitLab CI, CircleCI, and Azure Pipelines all use YAML for workflow definitions.
Configuration
Spring Boot, Ansible, Helm charts, ESLint, Prettier, and many other tools use YAML config files.
How to Use
Choose direction
Select YAML to JSON or JSON to YAML using the toggle at the top of the converter.
Paste your data
Paste YAML or JSON into the input panel, or click Sample to load an example.
Instant conversion
Output appears in real time as you type. Errors are shown with descriptive messages.
Copy or swap
Copy the output to clipboard, or use Swap to reverse the conversion direction.
Frequently Asked Questions
YAML (YAML Ain't Markup Language) is a human-readable data serialization format commonly used for configuration files. It uses indentation to represent structure, making it easy to read and write.
YAML uses indentation-based syntax and supports comments, while JSON uses braces and brackets. YAML is more human-readable, JSON is more widely supported by APIs. YAML is a superset of JSON, meaning valid JSON is also valid YAML.
Yes, completely free with no limits. Convert as much YAML and JSON as you want, no account required. Everything runs in your browser.
Yes. All conversion happens entirely in your browser using JavaScript. Your data never leaves your device and is never sent to any server.
Our parser supports key-value pairs, nested objects (2-space indentation), arrays (dash syntax), strings (plain, single-quoted, double-quoted), numbers, booleans (true/false/yes/no), null (~), multi-line strings (| and >), inline arrays/objects, and comments (#).
Yes! Use the toggle at the top to switch between YAML to JSON and JSON to YAML modes. The conversion works both ways with proper formatting.
Common YAML errors include incorrect indentation (must be consistent, typically 2 spaces), missing spaces after colons, tabs instead of spaces, and unquoted special characters. Check the error message for details.
YAML is widely used in Docker Compose, Kubernetes manifests, GitHub Actions, GitLab CI/CD, Ansible playbooks, Helm charts, Swagger/OpenAPI specs, Spring Boot configuration, and many other DevOps and configuration tools.
Yes! Unlike JSON, YAML supports comments using the # character. Comments can be on their own line or at the end of a line (inline). Our converter strips comments during conversion since JSON does not support them.
2 spaces is the standard convention for YAML files. Some projects use 4 spaces. Never use tabs in YAML — the YAML specification explicitly forbids tab characters for indentation.