Duplicate %YAML Directive – Remove Repeated YAML Version Directives

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A YAML document cannot repeat the %YAML version directive in the same directive section. Keep one version declaration before the document start marker.

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YAML directive duplication troubleshooting

How to fix a duplicate %YAML directive

The sample declares %YAML 1.2 twice before one document. A directive section may not repeat the YAML version directive, so the parser rejects the stream before it reaches the service mapping. This tool is free to use. No account or payment is required.

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What you can do here

  • YAML 1.2 parser validation
  • Duplicate mapping key detection
  • Preloaded broken YAML example
  • Readable parser feedback
  • .yaml and .yml file import
  • Browser-local processing

Steps

  1. Inspect the directive lines before the first --- document marker.
  2. Remove repeated %YAML version directives and keep the intended one.
  3. Validate again and check any generated or concatenated source that created the duplicate header.

Duplicate directives often come from concatenation

Templates or build steps can accidentally combine two YAML headers into one directive section. Fix the generator as well as the current output if the duplicate directive keeps returning.

A directive applies to the document that follows

Keep directive metadata at the stream boundary and separate it from data with ---. Ordinary application configuration usually does not need repeated version declarations inside the content itself.

Repeated YAML version directive example

Keep a single %YAML 1.2 line before the explicit document start.

Invalid YAML

%YAML 1.2
%YAML 1.2
---
service: api

Corrected YAML

%YAML 1.2
---
service: api

Common questions

Frequently asked questions

Can I put %YAML 1.2 twice before one document?

No. Repeating the YAML version directive in the same directive section is invalid.

Does every YAML document need a %YAML directive?

No. Most configuration documents omit it unless an explicit version directive is useful for the workflow.

What should follow a YAML directive section?

An explicit --- document start marker separates directives from the following YAML document content.

Recommended next steps

YAML Directive Missing Document StartAdd the required --- document start after a YAML directive section.Multiple YAML DocumentsDiagnose a YAML stream with more than one document when a single document is expected.YAML Validator Online – Check YAML SyntaxPaste any YAML document and inspect parser feedback locally.

Debugging a specific YAML issue? Browse YAML troubleshooting.