Does this support the full YAML spec?

No, it supports a common subset: nested mappings, lists, scalars, and inline flow arrays — not anchors or multi-line block scalars.

Is my YAML sent anywhere?

No, all parsing happens locally in your browser.

What happens if my YAML is invalid?

You'll see a clear error message pointing to the problematic line.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

YAML Validator

Validate YAML and preview it as JSON.

Support

Works Offline

Privacy First

No Login

No API

This validator supports a common subset of YAML: nested mappings, lists, scalars, and inline flow arrays. It does not support anchors, multi-line block scalars, or full YAML 1.2 spec features.

YAML Input

Valid — JSON preview

{
  "name": "Ada",
  "age": 28,
  "roles": [
    "admin",
    "editor"
  ],
  "address": {
    "city": "London",
    "zip": "E1 6AN"
  }
}

About the YAML Validator

Paste YAML to validate its structure and see a live JSON preview of nested mappings, lists, and scalars, with clear error messages when the indentation or syntax is invalid.

Examples

Simple mapping

name: Ada
age: 28

Output

{"name":"Ada","age":28}

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-07 · Runs entirely in your browser