YAML Formatter

A YAML formatter takes hard-to-read YAML and re-indents every mapping and sequence so the document structure is instantly visible. Our free online YAML formatter parses the dominant block constructs (mappings, sequences, nested indentation, quoted scalars, flow collections, block scalars, anchors, and comments), checks that the indentation is consistent, and re-serializes with clean, uniform indentation. It can also produce a compact version with comments and blank lines removed.

Yes — 100% private. All parsing, formatting, and validation is performed entirely in your browser using JavaScript. Nothing is ever uploaded to a server, so configuration files (docker-compose.yml, .github/workflows, Kubernetes manifests, Ansible playbooks, CI/CD pipelines) and API samples are safe to paste. The tool even works offline after the page has loaded, and your input is stored only in your own browser for convenience.

Unlike JSON and XML, YAML uses indentation to define structure — the nesting of every mapping and sequence is determined by spaces alone. Inconsistent indentation is the most common source of YAML errors: a key indented by three spaces while its siblings use two usually breaks the document or silently changes its meaning. Our formatter normalizes indentation to a single consistent width (2 or 4 spaces) and flags mixed indentation so your file is always structurally predictable.

Yes. Anchors (&name) and aliases (*name) — used to reuse blocks of configuration — are preserved verbatim, as are explicit tags (!!str, !custom) and merge keys (<<: *anchor). The formatter keeps them attached to the correct value while re-indenting the surrounding structure, so reusable config stays reusable.

The most common causes of YAML errors are: tabs used for indentation (tabs are not allowed), inconsistent indentation between sibling entries, mixing sequence items and mapping entries at the same level, a scalar value followed by an unexpected nested block, an unclosed quoted string, or an unclosed flow collection (missing } or ]). Our formatter highlights the offending line so you can fix it quickly.

Formatted mode re-indents your YAML with clean, consistent spacing while preserving comments and document markers. Compact mode removes comments and blank lines, producing the tightest readable version — useful for trimming config files before sharing or embedding. Both modes keep block scalars (| and >) and their content intact, since that content is significant.

Yes. Literal (|) and folded (>) block scalars are preserved with their content indentation normalized, and flow collections ({ ... } and [ ... ]) that span multiple lines are folded into a single line with consistent spacing. Quoted strings that span lines are also merged correctly. The output stays valid YAML that parses to the same data.

Yes — completely free, with no registration, no sign-up, no premium tier, and no data collection. All formatting happens locally on your device. Pair it with our JSON formatter, JSON validator, and XML formatter to cover all your structured-data needs in one place.