Invalid YAML Indentation
YAML uses indentation to express structure. Unlike JSON, a single wrong space can change nesting or make a document unparseable. Most parsers require spaces (not tabs) and consistent depth per block. Errors often mention 'mapping values are not allowed here' or 'found character that cannot start any token'.
Spaces, not tabs
Use two spaces per indent level in most style guides. Mixing tabs and spaces breaks parsers silently in some editors. Configure your editor to insert spaces when you press Tab.
Align list items
List entries (`- item`) must align with sibling keys at the same level. A dash one space too far left attaches to the wrong parent object.
Validate before deploy
Convert YAML to JSON with the YAML to JSON tool to surface line-level issues, then validate resulting JSON if your pipeline expects JSON downstream.