YAML Editor

Write, format and validate YAML with a live JSON preview. Everything runs locally.

YAML

app:
  name: OpenToolkit
  private: true
  tools:
    - yaml
    - json
    - markdown
  settings:
    theme: violet
    uploads: false

JSON preview

{
  "app": {
    "name": "OpenToolkit",
    "private": true,
    "tools": [
      "yaml",
      "json",
      "markdown"
    ],
    "settings": {
      "theme": "violet",
      "uploads": false
    }
  }
}

How to format and validate YAML

Add your YAML. Paste it into the editor, or upload a local .yaml/.yml file.
Format or validate. Choose "Format" to normalize it, or "Validate" to check its syntax.
Export. Copy the YAML, or download the result as YAML or JSON.

What happens to your data

Parsing, formatting and validation all run in your browser tab. An uploaded file is read into memory on your device and never sent to OpenToolkit.

Because there's no upload, there's no server-side size limit — a very large file is bound only by your browser's available memory and performance.

What this editor supports

InputPasted YAML, or an uploaded YAML file

FormattingNormalizes indentation and structure

ValidationSyntax-error checking

PreviewLive JSON preview of the parsed document

OutputDownload as YAML or JSON

ProcessingEntirely in your browser tab

Common reasons to use this editor

Track down a stray indentation error in a Kubernetes manifest or CI config.
Convert a YAML config into JSON for a script or another tool.
Tidy up hand-written YAML before committing it to a repository.
Confirm a docker-compose file actually parses before you deploy it.

Frequently asked questions

Is my YAML uploaded anywhere?

No. Parsing, formatting and validation all happen in your browser tab.

Can I convert JSON to YAML?

Not with this tool — it converts YAML to JSON. There's currently no reverse direction; try the JSON Formatter for JSON-side editing.

What happens if my YAML is invalid?

Validate reports the parsing error so you can locate the problem line.

Can I upload a file directly?

Yes — upload a local .yaml or .yml file to load it into the editor.

Is there a file size limit?

No fixed limit, but very large files can slow things down since parsing happens in one browser tab.

Can I download the JSON version?

Yes — the live JSON preview can be downloaded alongside the formatted YAML.

Last reviewed: August 2026