BYTETOOLS

YAML Validator

Validate YAML online and catch the errors that break CI: tabs, bad indentation, duplicate keys, missing spaces after a colon and unclosed quotes.

Drop a .yml or .yaml file here or click to browse

What is the YAML Validator?

The ByteTools YAML Validator checks a document for the mistakes that actually stop a pipeline: a tab character used for indentation, a key written as key:value with no space, a sequence item written as -name, duplicate keys inside one mapping, an unclosed quote or flow collection, and non-printable characters that snuck in from a copy and paste.

  • Flags tab indentation, the single most common YAML failure
  • Catches key:value and -item written without a space
  • Reports duplicate keys inside the same mapping
  • Detects unclosed quotes and unclosed [ ] or { } collections
  • Warns on inconsistent indent steps and trailing whitespace
  • Copyable report; nothing is ever uploaded

How to use the YAML Validator

  1. 1

    Paste the YAML you want to check, or drop a .yml or .yaml file onto the drop zone.

  2. 2

    Click Validate YAML.

  3. 3

    Read the pass/fail banner and the error and warning counts.

  4. 4

    Work through the findings table — each row gives the line, column, level and the exact problem — then use Copy report to share it.

About the YAML Validator

The ByteTools YAML Validator checks a document for the mistakes that actually stop a pipeline: a tab character used for indentation, a key written as key:value with no space, a sequence item written as -name, duplicate keys inside one mapping, an unclosed quote or flow collection, and non-printable characters that snuck in from a copy and paste.

Every finding is reported with its line number, column and the offending text, split into errors that will stop a parser and warnings that are only untidy. A pass or fail banner sits above the table so you know at a glance whether the file will load.

The check runs 100% locally in your browser. Your YAML is never uploaded or stored, so you can safely paste GitHub Actions workflows, Kubernetes manifests and Ansible playbooks that reference internal systems.

Frequently asked questions

Why does YAML complain about tabs?

The YAML specification forbids tab characters in indentation because a tab has no fixed width, so parsers cannot tell how deep a line is nested. Replace every leading tab with spaces and the error disappears.

How do I find a duplicate key in a YAML file?

Paste the file and click Validate YAML. Any key that appears twice inside the same mapping is reported with its line number, along with a note that the last value silently wins — which is usually the bug you are hunting.

Does this validator check my YAML against a schema?

No. It checks syntax and structure only, not whether the document matches a Kubernetes, GitHub Actions or OpenAPI schema. A file can pass here and still be rejected by a tool that expects particular key names.

What is the difference between an error and a warning here?

Errors stop a parser outright, such as tab indentation or an unclosed quote. Warnings flag things that parse fine but signal trouble, like inconsistent indent steps or trailing whitespace at the end of a line.

Is my file uploaded anywhere?

No. The whole check runs in your browser with JavaScript and nothing is transmitted or logged, which makes it safe for CI configuration and infrastructure files that mention internal hostnames.

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