What errors does it catch?

Tab characters in indentation (YAML forbids them), mismatched quotes, duplicate keys, invalid anchors, and malformed type tags. Each error has a line/column reference.

Does it validate against a schema?

Syntax only. For schema validation (JSON Schema draft 2020-12) use the dedicated YAML Schema Validator.

How does it handle multi-document files?

Every document (separated by `---`) is validated independently. An error in document 2 doesn't mask a later error in document 3.

Will it catch YAML 1.1 vs 1.2 differences?

The most common footguns — unquoted `yes`/`no`/`on`/`off` being parsed as booleans — are flagged as warnings in 1.1 mode and ignored in 1.2 mode.

YAML Validator | DevTools Surf

DevTools Surf

Example: YAML Validator

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

name: test
version: 1.0
items:
  - id: 1
    value: hello
  - id: 2
    value: world

Output

PASS Valid YAML — 1 document, 7 keys, depth 3

Documents: 1
Top level: mapping · 3 keys · name, version, items
Max depth: 3
Keys: 7
Anchors: 0 anchors, 0 aliases
Scalars: 3 strings, 3 numbers
Size: 7 lines, 84 bytes

About YAML Validator

Validate YAML syntax and structure. Part of the DevTools Surf developer suite. Browse more tools in the YAML collection.

Use Cases

DevOps engineers validating Kubernetes manifest files before applying
CI/CD engineers checking GitHub Actions or GitLab CI pipeline configs
Backend devs verifying Docker Compose file syntax
Platform engineers validating Helm chart values files

Tips

Watch for tab characters, which are illegal in YAML syntax
Check indentation consistency across all nested levels
Validate before deploying to catch missing colons or dashes

Fun Facts

YAML originally stood for 'Yet Another Markup Language' but was renamed to 'YAML Ain't Markup Language' to emphasize its data focus.
YAML 1.0 was first released in May 2004, created by Clark Evans, Ingy dot Net, and Oren Ben-Kiki.
The 'Norway problem' in YAML refers to how unquoted 'NO' is parsed as boolean false, which caused real bugs in country code lists.

FAQ

What errors does it catch?: Tab characters in indentation (YAML forbids them), mismatched quotes, duplicate keys, invalid anchors, and malformed type tags. Each error has a line/column reference.
Does it validate against a schema?: Syntax only. For schema validation (JSON Schema draft 2020-12) use the dedicated YAML Schema Validator.
How does it handle multi-document files?: Every document (separated by `---`) is validated independently. An error in document 2 doesn't mask a later error in document 3.
Will it catch YAML 1.1 vs 1.2 differences?: The most common footguns — unquoted `yes`/`no`/`on`/`off` being parsed as booleans — are flagged as warnings in 1.1 mode and ignored in 1.2 mode.

Related YAML Tools

YAML Viewer YAML Formatter YAML Parser YAML Multi-Doc Splitter YAML Anchor Expander Docker Compose Validator HTML Validator JSON Validator