{ } Format & Compare

YAML Formatter & Validator

Format and validate YAML, or convert between YAML and JSON. Essential for Kubernetes, Docker, and CI configs.

Updated

Format YAML YAML ↔ JSON Validate Private

Loading YAML Formatter…

What this page sends

  • Your input: Processed in this tab and not sent to a server.
  • Share links: Share links put a Base64 copy of your input and output in the URL itself (after #d=). Anyone with the link can read it, so don't share a link that contains secrets.
  • Editor: On desktop screens the code editor (Monaco) is downloaded from cdn.jsdelivr.net; phones get a built-in lightweight editor instead.
  • Page load: Loading the page requests HTML, scripts and images from ByteKiln, fonts from Google Fonts, and sends Google Analytics page views, tool-usage events and catalog interactions (tool/category IDs, result status and whether a click followed search — never your input, output or search terms). Privacy & sharing

How the YAML Formatter & Validator Works

The ByteKiln YAML Formatter uses js-yaml, a full-featured YAML 1.2 parser, to parse and re-serialize your input. All processing runs locally in the browser.

Format YAML

Parses the YAML input and re-serializes it with consistent 2-space indentation, keeping key order. Catches and reports syntax errors including indentation problems, duplicate keys, and invalid anchors.

YAML to JSON

Parses the YAML document and serializes it as a pretty-printed JSON object. Useful when an API or tool requires JSON but your source config is in YAML.

JSON to YAML

Parses the JSON input and re-serializes it as human-readable YAML. Useful for creating editable config files from machine-generated JSON.

Limitations

  • Formatting re-serializes the parsed data, so comments are removed and anchors are renamed (&defaults becomes &ref_0). Keep the original if its comments matter.
  • It follows YAML 1.2 via js-yaml: yes/no/on stay strings (YAML 1.1 parsers read them as booleans), and an unquoted 012 is read as the number 12 — quote values like ZIP codes.
  • Custom tags such as !Ref or !Sub in CloudFormation templates are rejected by the default schema.
  • It checks YAML syntax, not a schema: a manifest that formats cleanly can still be invalid for Kubernetes.

FAQ

Short answers for the things developers usually ask before trusting a tool.

What is YAML used for?

YAML (YAML Ain't Markup Language) is a human-readable data serialization format used extensively in DevOps and infrastructure tooling. Kubernetes manifests, Docker Compose files, GitHub Actions workflows, Ansible playbooks, and most CI/CD pipelines (GitLab CI, CircleCI, Travis CI) use YAML for configuration.

Does the formatter support multi-document YAML?

Yes. Documents separated by --- are formatted one by one and written back with --- between them, so a multi-resource Kubernetes manifest keeps every resource. YAML to JSON turns several documents into a JSON array with one element per document. Empty documents, such as a trailing ---, are dropped.

What is the difference between YAML and JSON?

YAML is a superset of JSON — valid JSON is also valid YAML. YAML adds comments, multiline strings, anchors/aliases for repeated values, and a less verbose syntax. JSON is simpler and more portable for APIs. YAML is better for human-edited config files; JSON is better for machine-generated data.

Can I use this to validate a Kubernetes manifest?

Yes. Paste the manifest and switch to Format YAML mode. If the YAML is malformed, you'll see a specific error message with the line and column. Note that the formatter validates YAML syntax, not Kubernetes schema — it won't catch invalid API versions or missing required fields.

Is my YAML config sent to a server?

No. The YAML Formatter uses js-yaml in your browser, so your configuration is not sent to a ByteKiln server. If you press Share, the link itself carries a readable copy of your input, so don't share links that contain secrets.

Related tools

Useful follow-ups when one conversion usually turns into three more.

format-compare

JSON Formatter

Format, validate, and minify JSON instantly with a browser-first editor.

format-compare

SQL Formatter

Format raw SQL with dialect support for SQL Server, MySQL, PostgreSQL, SQLite, and more.

code-api-conversion

JSON → C#

Convert JSON payloads into C# classes with nested types, arrays, DateTime, and Guid detection.

Want the background and worked examples? There's a longer write-up.

Read the YAML Formatter guide