YAML Formatter & Validator

Kubernetes YAML Validator

Kubernetes manifests — Deployments, Services, ConfigMaps, Ingress rules — must be perfectly formatted YAML. A single indentation mistake silently breaks your rollout. Paste your manifest here to validate the YAML structure before applying it with kubectl. The tool catches indentation errors, duplicate keys, and syntax problems instantly.

Docker Compose Validation

Docker Compose files are sensitive to whitespace and indentation. Paste your docker-compose.yml here to check for YAML errors before running docker compose up. Converts cleanly between the YAML you write and JSON if you need to inspect the parsed structure.

GitHub Actions Workflow Linting

GitHub Actions workflows are YAML files that fail silently if malformed — you only find out after the push. Validate your .github/workflows/*.yml files here before committing. Catches common issues like incorrect indentation under steps, missing colons, and improperly quoted strings.

YAML to JSON Conversion

Many APIs accept JSON but configuration is written in YAML. Use this tool to convert YAML config files to JSON for use in APIs, test fixtures, or debugging. The conversion is instant and lossless — all data types, arrays, and nested objects are preserved.

Ansible Playbook Syntax Check

Ansible playbooks are notoriously picky about YAML structure. Use this tool to verify your playbook syntax before running ansible-playbook. The formatter also normalizes indentation consistently across your tasks and variables.

Bad indentation

# Wrong
spec:
   containers:
  - name: app   # mismatched indent

YAML uses spaces only — no tabs. Indentation must be consistent within a block. Use 2 or 4 spaces per level and never mix them. The formatter normalizes this automatically.

Duplicate key

name: alice
age: 30
name: bob  # duplicate!

Each key in a YAML mapping must be unique at the same level. Duplicate keys are technically undefined behavior — some parsers silently take the last value, others error. Remove or rename the duplicate.

Missing colon after key

apiVersion v1  # missing colon
kind: Service

Every key-value pair needs a colon and a space: key: value. A missing colon causes the parser to read the whole line as a scalar string instead of a mapping.

Unquoted special characters

message: Hello: World  # colon in value
version: 1.0.0-beta

Values containing colons, # characters, brackets, or leading/trailing spaces must be quoted. Use single quotes for literal strings (no escape sequences) or double quotes when you need escape sequences like \n.

Tab characters

key:
	- item1  # tab indentation

YAML does not allow tab characters for indentation — this is one of the most common gotchas from copying YAML out of code editors with tab indentation configured. Replace all tabs with spaces.

Is my YAML data secure?

Yes — all processing happens entirely in your browser using JavaScript. Your YAML is never sent to any server. We don't collect, store, log, or transmit your data in any form. Once the page loads, every feature works without any network requests.

Can I validate Kubernetes YAML here?

Yes. This tool validates the YAML syntax of any Kubernetes manifest — Deployments, Services, ConfigMaps, Pods, Ingress, and more. It catches indentation errors, duplicate keys, and malformed structure. Note: it validates YAML syntax only, not Kubernetes-specific API rules like valid apiVersion values or required fields.

Can I use this for Docker Compose files?

Absolutely. Paste your docker-compose.yml file and the validator will check for YAML syntax errors before you run docker compose up. The formatter also normalizes indentation so your file is consistently structured.

Can I validate GitHub Actions workflows?

Yes. GitHub Actions .yml files are standard YAML and this tool validates their syntax. It's useful for catching indentation issues under steps:, missing colons, and improperly quoted strings before you push and trigger a failed run.

Can I convert JSON to YAML?

Yes. Paste JSON into the editor and the tool auto-detects the format, switching the primary button to JSON → YAML. The conversion handles nested objects, arrays, strings, numbers, and booleans. You can also convert YAML to JSON with the same button.

What YAML features are supported?

The formatter supports the full YAML 1.2 specification: anchors (&) and aliases (*), multi-line strings (| and > block scalars), complex keys, multi-document files separated by ---, comments, and all standard data types including booleans, null, integers, and floats.

What indentation options are available?

You can choose 2 spaces (default), 4 spaces, or 8 spaces. The setting applies to both YAML formatting and JSON → YAML conversion. 2 spaces is standard for Kubernetes and most DevOps tooling.

Does this work offline?

Once the page is loaded, all features work without an internet connection. There are no API calls — everything runs client-side in your browser.

What's the difference between YAML and JSON?

YAML is a superset of JSON designed to be more human-readable. YAML uses indentation instead of braces, supports comments (# ...), and has cleaner syntax for lists and strings. JSON is more widely supported in APIs and programming languages. Use YAML for configuration files; use JSON for data interchange and APIs.

Why does my YAML look different after formatting?

The formatter parses your YAML into a data structure and re-serializes it. This normalizes quoting (removing unnecessary quotes), ordering (alphabetical by default in js-yaml), and indentation. The data is identical — only the formatting changes. If something looks unexpected, compare the formatted output with the original carefully.