YAML ↔ JSON Converter

About the simplified YAML parser

YAML is a data serialization format widely used in configuration files (Docker Compose, Kubernetes, CI/CD, etc.). The full spec is large and full of advanced features. To keep this site 100% static and dependency-free, the parser here is a custom implementation that covers the most common subset of YAML — enough for most everyday config files.

What is supported

• Maps (key: value) and lists (- item).
• Indentation-based nesting using spaces.
• Scalars: string, number (integer and decimal), boolean (true/false) and null (null or ~).
• Single and double quotes in values and keys, with basic escapes inside double quotes (\n, \t, \", \\).
• Comments with # (including at the end of a line).
• Compact form - key: value for lists of objects.
• Empty collections [] and {}.

What is NOT supported

• Anchors and aliases (&, *).
• Tags (!!str, !!int, etc.).
• Multiple documents in the same file (the --- separator is ignored; use one document at a time).
• Literal and folded blocks (| and >).
• Non-empty inline collections ([1, 2, 3] or {a: 1}) — use the indented block form instead.
• Tabs in indentation (standard YAML doesn't allow them either) — use spaces.

If the input uses an unsupported feature, the tool shows a readable error message instead of silently producing an incorrect result.

Frequently Asked Questions (FAQ)

Why not use a ready-made YAML library?

The site is static, with no build step or external dependencies (beyond what's required for ads). A lean, custom parser keeps that promise and runs entirely in your browser.

Is a string that looks like a number preserved?

Yes. When generating YAML from JSON, text values that would look like numbers, booleans or null are automatically wrapped in quotes, so that reading them back still treats them as text.

I got an indentation error. What should I do?

Check that you're using spaces (not tabs) and that the levels are consistently aligned. The error message indicates the problematic line.