YAML to JSON Converter

How to Use the YAML to JSON Converter

1. Paste YAML into the input pane. Docker Compose files, GitHub Actions workflows, Kubernetes manifests, Ansible playbooks, and .yml configs from Rails, Django, or Hugo all work.
2. Pick an output style: 2-space JSON (most common), 4-space JSON (older Python style), or minified JSON on a single line (good for piping into another tool).
3. Click Convert. Valid YAML becomes structured JSON on the right; malformed input gets an error message that points at the offending line.
4. Copy the JSON with the clipboard button or drop it into the sibling JSON-to-YAML converter to round-trip and confirm semantics are preserved.

What It Does and How It Works

YAML is block-structured by indentation, which makes a simple parser more involved than it looks. The converter tokenises lines into one of four categories: block sequence items (starting with - ), block mapping entries (a key followed by :), scalar continuations, and structural markers (---, ...). Indentation is tracked with a stack of column offsets so nested sequences inside mappings and mappings inside sequences nest correctly. Scalar values are classified: unquoted tokens that match the YAML number grammar become JSON numbers, the literal tokens true, false, and null become the JSON equivalents, and everything else stays as a JSON string.

Once the input is parsed into a JavaScript object, JSON.stringify does the output formatting with the indent you selected. Quoted strings in the source (single or double) are always treated as strings regardless of content, which is how you preserve numeric-looking strings like ZIP codes or version numbers. Flow-style collections ({ key: value } and [ a, b ]) are handled alongside block style. Folded and literal block scalars (> and |) collapse or preserve newlines per YAML 1.2.

Real Use Cases

• Copying a Kubernetes manifest into a tool that only accepts JSON API payloads, such as curl against /api/v1/namespaces.
• Debugging a CI workflow by converting .github/workflows/ci.yml to JSON and viewing it in a JSON path explorer.
• Feeding a config file into a JSON Schema validator that does not speak YAML natively.
• Teaching the difference between YAML tag inference and explicit typing by seeing what JSON types fall out.
• Embedding a small config snippet into JavaScript code that uses JSON.parse for portability.
• Auditing a Helm chart or Terraform override.yml for hidden duplicate keys, which JSON forbids but some YAML parsers silently accept.

Edge Cases and Pitfalls

• The Norway problem. YAML 1.1 famously parsed unquoted no as a boolean false, which caused country code "NO" to mean "disabled". YAML 1.2 removed these aliases, but many parsers are still in 1.1 mode. This converter follows YAML 1.2: only true, false, True, False, TRUE, and FALSE are booleans.
• Tabs are illegal for indentation. YAML 1.2 mandates spaces. A hidden tab will either produce an error or silently misnest your tree. Convert tabs to spaces before pasting if your editor inserted them.
• Multi-document files. YAML can contain several documents separated by ---. The converter uses the first document only; to convert all of them wrap them in a JSON array manually.
• Anchors and references. &anchor and *ref are basic YAML features that this lightweight parser may flatten or drop depending on complexity. Very tight Helm templates that rely on anchors should be fully rendered first.
• Null-valued keys. foo: with nothing after the colon is a key mapping to null, which round-trips through JSON as "foo": null. Some consumers expect the key to be absent instead - check both.

YAML 1.2 Specification in Brief

YAML is defined at yaml.org/spec/1.2.2. The key design goal is that any valid JSON document is also valid YAML, so YAML is a strict superset. The additions YAML brings are block indentation, comments (#), anchors and aliases, explicit tags (!!str, !!int), and folded/literal multi-line strings. The 1.2 revision tightened type inference to avoid the YAML 1.1 booleans-everywhere problem and made JSON explicitly a subset. The YAML test matrix tracks how different parsers handle the standard; notably, Python\'s PyYAML defaults to YAML 1.1 mode and go-yaml v2 had edge cases that v3 fixed.

When to Use Another Tool

For production conversion, use yq (Go or Python editions) on the command line; it handles anchors, merges (<<:), and multi-document files in full compliance with the spec. yq eval -o=json file.yml is a one-liner equivalent. Inside JavaScript, the js-yaml library is the de facto parser and supports both 1.1 and 1.2 modes. Python has ruamel.yaml, which preserves comments and ordering better than PyYAML. This web tool is faster than any of those for quick spot conversions, especially on a laptop without Node or Python at hand, but treat it as a viewer rather than a canonical converter for mission-critical configs.