Valid YAML
name: webapp
replicas: 3
ports:
- 80
- 443About the YAML Validator playground
The YAML Validator checks whether a document is valid YAML and reports parse errors with line information so you can pinpoint and fix them. Because YAML relies on indentation, it is easy to introduce subtle errors like a stray tab, inconsistent spacing, an unclosed quote, or a misaligned list item, and the validator surfaces exactly where parsing failed. YAML (YAML Ain't Markup Language) is a human-readable serialization format widely used for CI configuration, Kubernetes manifests, and application settings.
Validation runs entirely in your browser, so your YAML is never uploaded or stored on a server, keeping configuration with sensitive values safe. Paste a document to instantly confirm it is well-formed or get a clear message about the offending line. This helps catch indentation mistakes and quoting issues before a pipeline or deployment tool rejects them, saving a round-trip through CI just to discover a formatting typo.
HostedYAML Validator runtime
mainentry file
single fileworkspace
stdinprogram input
How it works
1
Write
The main file is the entry point for each run.
2
Give it input
Use the Input panel to pipe standard input to your program when it needs data.
3
Run
Run sends your code to a fresh hosted runtime and streams the result into the output panel.
4
Keep or share
Your draft stays in this browser, and Share creates a separate snapshot link.
External resources
- yaml.org— Official website
Invalid: tab indentation
name: webapp
ports:
- 80
# Error: tab characters are not allowed for indentationInvalid: bad mapping indentation
server:
host: localhost
port: 5432
# Error: inconsistent indentation in mappingInvalid: unclosed quote
title: "Hello world
# Error: unexpected end of stream, missing closing quoteValid: nested map and inline collections
service:
name: api
env: [dev, prod]
limits: { cpu: 2, mem: 512Mi }
# Valid: nested mapping plus flow-style sequence and mappingInvalid: missing space after colon
name:webapp
port: 8080
# Error: a mapping needs a space after the colon, e.g. 'name: webapp'Valid: multi-document with block scalar
---
description: |
line one
line two
---
count: 2
# Valid: '---' separates documents; '|' keeps newlines in the block scalarValid: anchors and aliases
defaults: &defaults
retries: 3
timeout: 30
prod:
<<: *defaults
timeout: 60
# Valid: '&' defines an anchor, '*' references it, '<<' merges the mapInvalid: duplicate mapping key
name: a
name: b
# Error: duplicate key 'name' in the same mapping is not allowedHow it works
The editor uses Monaco, the engine behind VS Code, with language-aware editing tools and familiar keyboard controls.
How it works
Paste a YAML document into the validator
It parses the YAML and reports the offending line on failure
Fix the flagged line and re-check until it is well-formed
Errors it catches
Stray tabs and inconsistent indentation
Misaligned list items and mapping keys
Unclosed quotes and quoting mistakes
Privacy
Validation runs entirely in your browser
Config with sensitive values is never uploaded or stored on a server
Good for
Checking CI configs, Kubernetes manifests, and app settings
Avoiding a round-trip through CI just to find a formatting typo
Every shortcut, searchable:
Editing
Undo
Ctrl+Z
Redo
Ctrl+⇧+Z
Select next occurrence
Ctrl+D
Delete line
Ctrl+⇧+K
Move line up / down
Alt+↑ / ↓
Copy line up / down
Alt+⇧+↑ / ↓
Toggle comment
Ctrl+/
Indent line
Ctrl+]
Outdent line
Ctrl+[
Navigation
Find
Ctrl+F
Find & replace
Ctrl+H
Go to line
Ctrl+G
Go to symbol
Ctrl+⇧+O
Selection
Select all
Ctrl+A
Select line
Ctrl+L
Select all occurrences
Ctrl+⇧+L
Shortcuts follow your OS — ⌘ becomes Ctrl on Windows and Linux.
It checks whether text is valid YAML and reports parse errors with line information so you can locate indentation and syntax problems.
No. Validation runs in your browser and nothing is sent to a server, so sensitive config stays private.
Yes, it is free with no sign-up or installation.
YAML forbids tab characters for indentation and requires spaces. A single tab is one of the most common causes of a YAML parse error.
It means the document is well-formed YAML, not that the keys and values match what a specific tool expects. Schema or application-level checks are separate from syntax validation.
Input
Issues
No input to validate