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Tools / Validators & Inspectors

YAML syntax checker

Check the supported YAML syntax and value restrictions.

Input

0 UTF-16 code units

Optional local draft

Saving stores a plaintext draft in this browser on this device. Do not save secrets or use this on a shared device. Nothing is saved or loaded automatically. Reset does not delete a saved draft; use Delete local draft.

No draft has been loaded.

Import a local text file

Output

Work through the task
Check supported YAML syntax and values.
  1. Enter YAML and choose Check YAML.
  2. A successful result checks this parser’s supported subset. It does not check an application schema.
  3. Review the result before copying or downloading. Editing an input invalidates the previous result; keep an original if the transformation matters.
Example to check
Duplicate keys, aliases and custom tags are rejected; a plain supported mapping can pass.
Limits and output behavior
Source is limited to 100,000 characters. JSON/YAML/TOML have 10,000 values and 40 data levels; XML has separate node/attribute and element-depth guards. Comments, numeric spelling and other lexical formatting may normalize. YAML aliases/custom tags and TOML null values are unsupported.
Troubleshooting
Use one supported YAML document without aliases or custom tags. Fix a reported duplicate key or unsupported type before rerunning.
Questions
Does this check a YAML application schema?
No. It checks the supported syntax and value subset, not the rules of a particular application.
Input and privacy
Processing runs in this browser. Inputs are not saved automatically. An explicitly chosen local draft, where offered, is plaintext storage on this device. Downloaded files, clipboard contents and browser extensions have separate retention behavior.