YAML Indentation Error – Find and Fix Invalid Indentation
YAML uses indentation to define nesting. A line shifted to the wrong level can change the structure or make the document impossible to parse.
Read fixYAML error index
YAML Troubleshooting
Trace YAML indentation, mapping, sequence, quoting, directive, anchor, alias, and flow-style errors with parser-focused examples.
Diagnostic workflow
How to troubleshoot YAML problems
YAML failures often come from structure that is expressed by whitespace rather than punctuation. Preserve the original indentation while you isolate the failing block, then distinguish indentation problems from scalar, flow-collection, directive, or anchor syntax before editing nearby lines.
- Compare indentation levels with spaces made visible, and remove tab indentation before investigating more complex parser messages.
- Reduce the document to the smallest mapping or sequence that still fails so a distant block does not hide the real indentation boundary.
- Check quoted strings, flow collections, document markers, anchors, aliases, and block scalar headers only after the surrounding structure is aligned.
Browse focused fixes
Common YAML problems
24 troubleshooting pages
Tabs in YAML – Fix Tab Indentation Errors
Tabs are not valid block indentation in YAML. A file that looks aligned in an editor can still fail when leading tabs are used instead of spaces.
Read fixDuplicate Keys in YAML – Find Repeated Mapping Keys
Repeated keys make configuration ambiguous because consumers can disagree about which value wins. VetaTool validates YAML with duplicate mapping keys treated as errors.
Read fixMapping Values Are Not Allowed Here – YAML Error Fix
A colon followed by a space has structural meaning in YAML. An unquoted command or text value containing that sequence can be mistaken for another mapping entry.
Read fixCould Not Find Expected ':' – YAML Error Fix
A mapping key normally needs a colon separator. A missing separator can make the parser reinterpret the line and fail when the following mapping entry appears.
Read fixExpected <block end> – YAML Indentation Error Fix
Expected block end errors usually mean indentation changed before the current mapping or sequence could close cleanly.
Read fixYAML Sequence Indentation Error – Fix List Indentation
YAML sequence dash markers belong to a specific indentation level. A list item shifted left or right can leave the sequence or attach it to the wrong parent.
Read fixYAML Multiline String Indentation – Fix Block Scalar Errors
Content after | or > must stay indented as part of the block scalar. A line that de-indents too early can end the scalar and leave invalid YAML after it.
Read fixInvalid Escape Sequence in YAML – Fix Double-Quoted Strings
YAML double-quoted scalars interpret backslashes as escapes. A sequence such as \q is not a supported escape and makes the document invalid.
Read fixUnclosed Quoted String in YAML – Find Missing Quotes
A quoted YAML scalar must reach its matching closing quote. If the document ends first, later text can be consumed as part of the string or parsing stops with a missing-character error.
Read fixYAML Reserved Character Error – Quote @ and Backtick Values
YAML reserves @ and the backtick at the beginning of plain scalars. Quote values such as @home instead of leaving them bare.
Read fixMultiple YAML Documents Error – Fix Unexpected --- Separators
A YAML stream may contain multiple documents separated by ---, but VetaTool's YAML workspace validates one document at a time. A second document is therefore reported instead of silently ignored.
Read fixYAML Flow Sequence Missing Comma – Fix [ ] Lists
Flow-style YAML sequences use square brackets and commas between items. Adjacent mappings or collections without a comma cannot be parsed as separate list entries.
Read fixYAML Flow Mapping Missing Comma – Fix { } Objects
Flow-style YAML mappings use curly braces and commas between key/value pairs. A second key cannot start immediately after the first value without a separator.
Read fixInvalid YAML Alias – Fix Malformed *anchor References
A YAML alias begins with * and must include a valid identifier that refers to an anchor. A bare asterisk is not a complete alias value.
Read fixYAML Multiline Implicit Key – Keep Flow Keys on One Line
Strict YAML requires an implicit mapping key in a flow collection to stay on one line. Splitting the key from its colon can make the parser treat the flow pair as invalid.
Read fixUndefined Alias in YAML – Fix Missing Anchor References
A YAML alias can only reference an anchor that already exists in the document. A named *alias with no matching &anchor cannot be resolved.
Read fixMissing YAML Anchor Name – Fix Bare & Anchor Syntax
The & token starts a YAML anchor and must be followed by an anchor name. A bare ampersand cannot label a node for later alias references.
Read fixUnclosed YAML Flow Sequence – Fix Missing ] Brackets
A flow sequence opened with [ must eventually close with ]. If the document ends first, the parser cannot determine where the inline list stops.
Read fixUnclosed YAML Flow Mapping – Fix Missing } Braces
A flow mapping opened with { must close with }. Without the closing brace, the parser cannot determine where the inline mapping ends.
Read fixInvalid YAML Block Scalar Header – Fix | and > Indicators
YAML block scalar headers only allow specific chomping and indentation indicators after | or >. Arbitrary characters such as x make the header invalid.
Read fixYAML Directive Missing --- Document Start – How to Fix
A YAML directive section such as %YAML 1.2 must be followed by an explicit --- document start before ordinary document content begins.
Read fixContent After YAML ... Document End – Start a New Document
The ... marker explicitly ends a YAML document. Additional content needs a new document start instead of continuing as though the previous document were still open.
Read fixDuplicate %YAML Directive – Remove Repeated YAML Version Directives
A YAML document cannot repeat the %YAML version directive in the same directive section. Keep one version declaration before the document start marker.
Read fixUnderstand the underlying concepts
YAML guides
1 related guides
YAML Indentation Explained: Spaces, Sequences & Mapping Errors
Learn how YAML indentation defines mappings, sequences, nested blocks, and multiline scalars, with examples for tabs, spacing, and common parser errors.
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