YAML Formatter & Validator
Format YAML, validate syntax, and inspect parser diagnostics locally in your browser.
Format and validate YAML
Format one YAML 1.2 document or validate its syntax with precise error details.
- Lines
- 0
- Nodes
- 0
- Aliases
- 0
- Max depth
- 0
Parses one YAML 1.2 document with the core schema. Multi-document streams and invalid syntax are rejected.
Your YAML is formatted and validated locally in your browser and is not sent to a server.
Overview
What is YAML formatting?
YAML formatting parses a YAML document and writes its serialization with consistent spacing and indentation. It is useful when configuration files have become difficult to review after manual edits, generation, or copy-and-paste changes.
This tool combines formatting with syntax validation because both tasks require the same parser. It does not claim to validate the schema expected by Kubernetes, Docker Compose, GitHub Actions, OpenAPI, or any other application.
Workflow
How to format and validate YAML
- Paste one YAML 1.2 document into the input editor.
- Select two-space or four-space indentation.
- Choose Format YAML to create formatted output.
- Choose Validate YAML when you only need syntax diagnostics.
- Review any warning, error code, line, and column before using the document.
Example
YAML formatting example
Before
service: api
ports: [80,443]
labels: {region: us-east-1, tier: backend}After
service: api
ports: [ 80, 443 ]
labels: { region: us-east-1, tier: backend }Parser scope
What YAML validation checks
Validation uses YAML 1.2 with the core schema and strict parser behavior. It checks document structure, indentation, mapping syntax, sequences, quoted scalars, anchors, aliases, directives, duplicate mapping keys, and document boundaries within the parser’s scope.
A syntactically valid document may still be rejected by the program that consumes it. Field names, allowed values, resource kinds, and business rules require that program’s own schema or validation tooling.
Troubleshooting
Common YAML syntax errors
- Using a tab where block indentation requires spaces.
- Indenting a sequence or mapping at the wrong level.
- Leaving a flow collection such as
[a, b]or{ key: value }unclosed. - Repeating the same mapping key when unique keys are required.
- Referencing an alias before its anchor is defined.
- Pasting multiple documents into this single-document formatter.
Formatting limits
YAML presentation and semantic limits
YAML contains both data and presentation details. Formatting can change whitespace, flow style, quoting, or line wrapping without intending to change the parsed data. Comments, anchors, aliases, and directives are retained when represented by the parsed document, but exact source text is not guaranteed.
YAML implementations can also differ in supported schemas and custom tags. This tool uses the YAML 1.2 core schema rather than YAML 1.1 or an application-specific dialect.
Safety
Local processing and safety limits
- Input is limited to one million UTF-16 code units and output to two million.
- The parsed document is limited to 50,000 nodes and a supported depth of 100.
- Formatting serializes the YAML document tree without evaluating configuration content.
- Input, output, and diagnostics are rendered with safe text and form-value APIs.
- No YAML content is uploaded to Orbilyra or a third-party formatting API.
FAQ
Frequently asked questions
What does a YAML formatter do?
A YAML formatter parses a YAML document and serializes its structure consistently. This tool applies two-space or four-space indentation while retaining comments and YAML document metadata where the parser can represent them.
Does this tool also validate YAML?
Yes. Validate YAML parses one YAML 1.2 document using the core schema and reports parser errors with an error code and line and column when available.
Does formatting change YAML meaning?
Formatting is intended to retain the parsed YAML document, but presentation details may change. Always review documents whose applications depend on unusual tags, scalar styles, directives, anchors, or implementation-specific behavior.
Does YAML allow tabs for indentation?
No. YAML block indentation uses spaces. A tab used as indentation is reported as invalid syntax, although tab characters may appear inside some scalar content.
Does this formatter support multiple YAML documents?
No. It accepts one YAML document at a time. A stream containing multiple documents is rejected so that no document is silently ignored.
Are comments and anchors preserved?
The document-based formatter retains parser-recognized comments, anchors, and aliases when serializing. Whitespace and scalar presentation may still change, so formatting should not be treated as a byte-for-byte round trip.
Is YAML validation the same as validating an application configuration?
No. Syntax validation only confirms that the document parses within this tool’s YAML scope. It does not check Kubernetes, Docker Compose, GitHub Actions, OpenAPI, or another application-specific schema.
Is my YAML uploaded?
No. Formatting and syntax validation run locally in your browser, and this tool does not send the document to a formatting service.