Free Online YAML Formatter & Validator
Quick answer
Paste YAML to format it cleanly, validate it with exact line-and-column errors, or convert it to JSON — all instantly in your browser. This free YAML formatter never uploads your config files, needs no signup, and shows you the precise line that broke your document the moment you type it.
Last updated: October 16, 2026
YAML is everywhere — GitHub Actions, Docker Compose, Kubernetes, CI pipelines — and it is unforgiving about whitespace in ways that cost real time: a tab instead of two spaces, an unquoted colon, a missing space after a dash. This formatter watches your input as you type, points at the offending line when the parser trips, and renders a consistently indented result you can copy straight back into your pipeline. JSON conversion is one click because half of all YAML questions are really JSON questions in disguise.
Use the tool belowValid YAML — 480 B
name: codelive-studio
url: https://codelivestudio.cyou
price: 0
signup_required: false
privacy:
client_side: true
uploads: null
storage: browser-localStorage
tools:
- name: HTML/CSS/JS Playground
languages:
- html
- css
- javascript
live_preview: true
- name: JSON Formatter
features:
- beautify
- minify
- validate
- name: YAML Formatter
features:
- format
- validate
- convert
tags:
- free
- private
- no-signup
YAML Formatter & Validator runs entirely in your browser — nothing you paste or type is uploaded to any server, and no account is needed.
How do I format a YAML file online?
- 1
Paste your YAML into the left editor, upload a .yaml or .yml file, or press Sample for a realistic document with nesting, lists and nulls.
- 2
Check the status line: valid documents show a green badge with the byte size; broken ones show the parser's reason plus the line and column to fix.
- 3
Read the formatted output on the right with consistent 2-space (or 4-space) indentation — or switch the output to JSON to see the same data as JSON.
- 4
Copy or download the result, or press Reformat input to write the clean version back into the editor and keep editing.
What this YAML formatter does for you
Validation with real error locations
The parser reports the reason ("bad indentation of a mapping entry", "found character that cannot start any token") together with the exact line and column — turning "file.yml:23: did not find expected key" from a mystery into a one-line fix.
Consistent indentation, your width
Output is re-dumped with uniform 2-space or 4-space indentation and no line folding, so long values stay on one line and the document round-trips without surprises. Choose the width that matches your team's lint rules.
YAML to JSON in one click
Switch the output pane to JSON to see exactly what your YAML means as data — the fastest way to understand anchors, aliases and implicit typing, or to hand parsed values to JavaScript code that speaks JSON natively.
Config files that stay on your machine
Deployment manifests and CI configs routinely contain tokens, internal hostnames and secrets. Parsing happens in your tab with no upload endpoint, so pasting a docker-compose file with credentials exposes nothing to anyone.
Upload, copy, download
Read .yaml/.yml files straight from disk with the browser's FileReader, copy results to the clipboard, or download them as .yaml or .json — all processed locally, all free.
Auto-save between visits
Your document lives in your browser's localStorage and reappears when you return — the convenience of cloud editors without a cloud or an account.
CodeLive Studio vs Code Beautify vs Prettier (YAML plugin)
The common routes to formatted YAML differ in friction, privacy and where they fit in a workflow.
| What matters | CodeLive Studio | CodeBeautify YAML | Prettier + yaml plugin |
|---|---|---|---|
| Price | Free — no paid tier exists | Free, ad-supported | Free tool, needs setup |
| Account required | Never | No | No |
| YAML stays in your browser | Yes — parsed client-side only | Processed on their servers | Runs locally |
| Ads between you and the tool | Never inside the editor | Yes | None |
| Error line and column | Yes, live as you type | Yes, on paste | Via separate linter |
| YAML to JSON conversion | One click, output pane | Separate tool page | Not built-in |
| Setup effort | Open the page | Open the page | Install node, Prettier, plugin, config |
| Fits team CI lint rules | Manual copy-back | Manual | Yes (its strength) |
Based on publicly available information as of October 2026 — verify on each site if a detail is critical. Honest footnote: for enforcing YAML style across a whole repository, a CLI linter in CI is the right tool and no web page replaces it. This page wins the single-file loop: open, paste, fix, copy.
Why does YAML break so easily?
YAML's strength — human-readable structure without brackets — is also its fragility: structure is expressed by indentation, so whitespace is syntax. The four classics are tabs (illegal as indentation), inconsistent depth between sibling keys, missing spaces after list dashes or colons, and unquoted special characters. None of these look wrong to the eye, which is exactly why a formatter that names the failing line saves so much time.
The other recurring trap is implicit typing: a value like no, on, 07 or 3.10 is read as boolean false, boolean true, octal or float rather than text. The JSON view makes this visible instantly — switch the output pane and you see the data as the parser actually understood it, which is usually the moment the bug becomes obvious.
Is it safe to paste deployment files here?
Yes, by architecture. The page contains no upload endpoint — parsing and re-dumping run in your browser's JavaScript, and you can watch the network tab stay quiet while you work. Kubernetes secrets, GitHub Actions tokens and database URLs stay on your machine.
The page itself loads no ad networks or third-party trackers, so there is also no bystander script copying your keystrokes anywhere. The only persistence is your browser's localStorage auto-save, stored on your device and clearable at any time.
Questions this tool answers
- yaml formatter
- yaml formatter online
- yaml validator online
- yaml beautifier
- yaml to json converter
Frequently asked questions
How do I fix "bad indentation of a mapping entry"?
Check the line the error names and the one above it: siblings must sit at exactly the same depth, nested values must be deeper, and every level must use spaces (never tabs). Reformatting here normalizes all of it — paste the broken file, confirm the error, then copy the clean output.
Can YAML use tabs?
No — tabs are forbidden for indentation in the YAML specification precisely because they render differently in different editors. If your file contains tabs, the validator flags the exact line; the formatter's output always uses spaces.
What is the difference between formatting and validating?
Validation checks whether the document parses at all; formatting produces a cleanly re-dumped version with consistent indentation. This tool does both in one pass — a valid document gets formatted output, an invalid one gets a located error, every keystroke.
Does this convert YAML to JSON?
Yes — switch the output selector to JSON and the parsed data renders as formatted JSON you can copy or download. It is also a debugging lens: the JSON shows how YAML implicitly typed every value, so strings-that-became-booleans stand out immediately.
Are anchors and aliases supported?
Yes — the parser understands &anchors, *aliases and merge keys, and the JSON view shows the resolved result. The formatter's output re-dumps plain data without re-creating anchors, which is what most pipelines expect anyway.
Is there a file size limit?
No artificial one — multi-megabyte documents work within your browser's memory. Extremely large files may take a moment on each edit, but validation, formatting, copying and downloading all remain available.
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