YAML vs JSON: Differences and How to Convert
4 min read
YAML and JSON represent mappings, lists, strings, numbers, booleans, and null-like values, but their syntax and typical uses differ. JSON uses braces, brackets, commas, and quoted keys. YAML often uses indentation, key: value pairs, and hyphens for list items, making configuration files shorter but more sensitive to spacing.
Use JSON when you need a strict, widely supported data interchange format, especially for APIs. Use YAML when humans frequently edit configuration and comments are useful. The YAML to JSON converter translates in either direction, supports multiple YAML documents, and reports available YAML error line and column positions.
YAML vs JSON syntax with short examples
A JSON object might be {"name":"Ada","active":true}. Keys and string values use double quotes, properties are separated by commas, and braces define the object. A list uses brackets, as in ["red","blue"]. Standard JSON does not allow a trailing comma after the final item.
The equivalent YAML can be written on separate lines as name: Ada and active: true. A YAML list commonly uses one hyphen per line: - red followed by - blue. YAML also supports flow forms resembling JSON, but indentation-based block style is common in configuration files.
Both formats can represent the same basic data, yet YAML has a broader syntax with document markers, comments, anchors, tags, block strings, and several scalar styles. Conversion preserves the parsed data value, not every spelling or layout choice from the source.
Indentation and whitespace pitfalls in YAML
Indentation defines nesting in block-style YAML. Child keys and list items must align consistently beneath their parent. A line shifted by one space can move a value into the wrong structure or cause a parser error. Use spaces rather than tabs for YAML indentation and keep sibling entries at the same level.
JSON ignores most optional whitespace because braces and brackets define structure. That makes it visually noisier but less dependent on alignment. A JSON parser still requires correct commas, quotes, braces, and brackets, so each format has different common failure points.
The converter's Indent setting controls generated output and offers 2 spaces or 4 spaces. It does not repair ambiguous source automatically. When YAML is invalid, read the reported location, inspect the named line and nearby parent block, and correct the alignment or syntax.
How to convert YAML to JSON with Tools on Deck
Conversion runs after a short typing delay and stays in your browser. You can paste text, use Sample, or choose Open file for .yaml, .yml, .json, or plain-text input.
- Open the converter and select YAML → JSON.
- Paste YAML into Input · YAML or choose Open file to read a local document.
- Choose 2 spaces or 4 spaces under Indent for the generated JSON.
- Read Invalid YAML if conversion stops, including the line and column when the parser supplies them.
- Review Output · JSON and any note that multiple YAML documents were combined into an array.
- Copy the result or download
data.json; switch to JSON → YAML when you need the reverse conversion.
Comments and formatting do not round-trip
YAML supports comments beginning with # outside quoted scalar content. Standard JSON has no comment syntax. When YAML is parsed and converted to JSON, comments are lost because they are not part of the resulting data value.
Other source-level details may also change. Quoted and unquoted YAML strings can produce the same parsed string, block styles can become escaped JSON strings, and anchors are resolved into represented values rather than preserved as the original written structure. Converting back generates fresh YAML; it does not reconstruct the original file character for character.
If comments explain operational choices, keep the YAML source under version control rather than treating converted JSON as the sole master copy. Review generated output before replacing hand-maintained configuration.
Multiple YAML documents
One YAML stream can contain multiple documents, commonly separated by --- document markers. JSON has no directly equivalent multi-document stream in one ordinary JSON value. The converter parses every YAML document and, when more than one is present, combines their values into one JSON array.
A status note states the exact number of YAML documents combined. The array order follows document order. Consumers must expect that wrapper; a program designed for one top-level object may need each array element handled separately.
In the reverse direction, one JSON array converts to one YAML document containing a sequence. It is not automatically expanded into several --- separated documents. This distinction matters when a deployment tool interprets a multi-document YAML stream differently from a single document containing a list.
Where YAML and JSON are commonly used
YAML is common for human-edited configuration, automation definitions, and deployment files because indentation can reduce punctuation and comments can stay near settings. Its flexibility also means teams benefit from formatters, schema checks, and careful code review, especially around values that may be interpreted as particular scalar types.
JSON is common for web APIs, event payloads, browser storage, and machine-generated data because its grammar is smaller and parsers are broadly available. It maps naturally to objects and arrays in many programming environments. For API debugging, the JSON formatter can validate syntax and identify an error line and column.
Choose according to the consuming system first. A service that requires JSON will not accept YAML merely because the data is equivalent, and a configuration platform may rely on YAML-specific multi-document behavior.
Quick answers about YAML vs JSON
YAML is often shorter and supports comments, while JSON uses explicit punctuation and has no standard comments. YAML indentation is structural, so alignment mistakes can change nesting or trigger an error. JSON is especially common for APIs; YAML is especially common for configuration.
When converting YAML to JSON, comments and original formatting are not retained. Multiple YAML documents become a JSON array, and parser errors show a line and column when that location is available.