YAML Formatter & Beautifier Online 2026 - Fast, Secure & Private
Format, beautify, and validate YAML data instantly. 100% free, secure client-side processing. No data upload required. Works offline.
Key Features
- ✅ Auto-indentation
- ✅ Syntax highlighting
- ✅ Comment preservation
- ✅ Error detection
How to Use
- Paste your YAML configuration
- Select indentation size (2 or 4 spaces)
- Click Format to apply formatting
- Review the formatted output
- Check for any parsing issues
- Copy or download the clean YAML
- Deploy with confidence
- Use in version control for consistency
Expert FAQ
- My YAML uses a tab character for indentation and won't format — is that a bug?
No — the YAML spec explicitly disallows tabs for indentation (only spaces are permitted), so a tab-indented file fails to parse before formatting can even begin, the same way the formatter can't reformat any other unparseable input. Replace tabs with spaces in the source first; most editors have a "convert tabs to spaces" action for exactly this. - I have a multi-line string using the | (literal) block style — will formatting flatten it into one line?
No — block scalar styles (| for literal, > for folded) are preserved exactly as written, including the line breaks inside them, because converting them to a quoted single-line string would change the value's actual content (literal newlines vs no newlines) rather than just its presentation. The formatter only touches structural whitespace, never the content of a scalar value. - Does it preserve comments and where they're positioned relative to the surrounding keys?
Yes — comments are anchored to the line or key they follow in the source and stay attached to that same context after reformatting, rather than being collected and moved elsewhere. This is different from some "round-trip unsafe" YAML libraries that parse to a plain data structure and lose comments entirely on re-serialization; this formatter operates on the document structure directly to avoid that. - Can it fix YAML that has an indentation level that's simply wrong — like a child key indented less than its parent?
Only if the file is still parseable despite the inconsistency — the formatter standardizes indentation width (e.g. normalizing a mix of 2-space and 3-space indents to a consistent 2-space) for an already-valid document, but if the indentation error actually changes which key is a child of which (a genuine structural ambiguity, not just inconsistent spacing) the file won't parse at all, and reformatting can't guess the intended structure. Use the YAML Validator first to confirm the file parses before formatting it.
Technical Details
YAML's significant whitespace makes formatting a stricter operation than it is for brace-delimited formats: the formatter can only standardize the spacing of an already-parseable document (normalizing inconsistent indentation widths, aligning list markers, fixing trailing whitespace) — it cannot "fix" indentation that's wrong enough to create real structural ambiguity, because at that point the parser itself can't determine the intended nesting, and there's no single correct interpretation to format toward. Tabs are rejected outright rather than silently converted, since the YAML spec disallows them for indentation entirely; converting tabs to spaces changes how many characters of indentation actually exist and could shift nesting level, so that decision is left to you rather than guessed at silently. Scalar block styles — literal (|, preserves line breaks exactly) and folded (>, folds line breaks into spaces) — are preserved as-is rather than normalized to quoted single-line strings, because the choice of style is itself meaningful: a multi-line shell script embedded in a CI config under | needs its newlines preserved exactly, and rewriting it as an escaped one-liner would be a content change disguised as a formatting change. Comments are kept attached to their original position in the document tree rather than being stripped and reinserted from a flat list, which avoids a common failure mode in YAML tooling where a library parses to a plain object, loses comment associations, and reattaches them in the wrong place (or drops them) on re-serialization. If your file fails to format at all, that almost always means it isn't valid YAML in the first place — check it with the YAML Validator, which will point at the specific line where parsing breaks down.