YAML Indentation Error Example: Off-by-One Space
Check YAML-like lines for indentation, keys, duplicates, and quotes. This is not a full YAML 1.2 parser.
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About this tool
This page opens the YAML validator preloaded with a short server configuration that contains a real, common mistake: after two keys nested four spaces deep, a following key drops back to three spaces instead of returning to the enclosing block's two-space level. YAML has no tabs-vs-spaces tolerance and no fixed indent width, so a single stray space like this does not average out — it simply does not match any open block, and the file is invalid. The failing check below runs live the moment the page loads.
This is one of the most common ways real YAML breaks in practice: hand-editing a file in an editor that does not enforce a consistent indent size, or pasting a fragment from somewhere with different spacing than the surrounding block. Unlike a duplicate key or a stray tab, an off-by-one indentation slip is easy to miss by eye, especially in a deeply nested Kubernetes manifest or CI pipeline file — which is exactly why an automated check catches it faster than a human reviewer scanning a diff.
Replace the sample text with your own file to see the same line-and-column reporting applied to your configuration. Once you understand the failure pattern here, compare it against the yaml-config-example preset to see the same structure with consistent indentation passing cleanly.
Example. The line key: value is accepted. A second key: other at the same indent fails with Duplicate key detected. A leading tab fails with YAML does not allow tab characters for indentation.
Limit. This is a line scanner, not a YAML 1.2 parser. Anchors, aliases, tags, and flow collections are not implemented. A pass does not mean a Kubernetes or CI schema is satisfied.