JSON to YAML Converter Online

YAML Is a Superset of JSON

Since YAML 1.2 the specification states that every valid JSON document is also a valid YAML document. Paste raw JSON into a YAML parser and it will accept it. That fact makes this conversion less of a translation and more of a reformatting: the data model on both sides is the same set of maps, sequences, and scalars, and only the syntax changes.

What you gain is readability and comments. What you gain in risk is whitespace sensitivity and a set of implicit typing rules that surprise people. The rest of this page is about both.

Side by Side Example

A deployment configuration, first as JSON and then as the block style YAML the converter produces.

Every brace, bracket, comma, and quotation mark is gone. The structure is now carried entirely by indentation and by the hyphen that marks a sequence item.

Indentation Rules

• Two spaces per level is the near universal convention. The spec only requires consistency, but every linter and every example you will meet uses two.
• Tab characters are forbidden as indentation. This is a hard rule in the specification, not a style preference, and a stray tab produces a parse error that often points at the wrong line.
• A sequence under a mapping key may be indented or written flush with the key. Both are legal, which is why you will see two different looking styles in real repositories.
• Sibling keys must line up in the same column exactly. A single extra space silently changes the meaning by nesting the key under its predecessor.

Configure your editor to show whitespace and to insert spaces rather than tabs before you edit YAML by hand. It removes an entire category of bug.

Block Style and Flow Style

YAML supports two ways of writing collections. Block style uses indentation and is the readable default. Flow style uses braces and brackets and looks exactly like JSON, which is why the superset claim holds.

Flow style is useful for short lists where a vertical block would waste six lines to say very little. Mixing the two in one file is entirely legal and often produces the most readable result.

When Strings Need Quoting

YAML infers scalar types from the shape of the text, and unquoted values are resolved against a set of patterns. This is convenient right up until a value happens to match a pattern you did not intend.

The Norway problem

The best known example: a list of ISO country codes containing NO for Norway. Under YAML 1.1 rules, the unquoted token no is a boolean, so Norway silently becomes false and a country vanishes from the list. The same trap catches ON for Ontario and, in some parsers, the chemical formula shorthand and any field where a two letter code is legitimate data. Quote your codes.

Multi-line Strings, Comments, and Anchors

Three YAML features have no JSON equivalent at all, and they are the main reason teams prefer YAML for configuration.

The pipe indicator keeps line breaks, which is what you want for shell scripts and embedded code. The greater than indicator folds wrapped lines into one paragraph, which is what you want for prose. Anchors and aliases let you define a block once and reuse it, and the merge key pulls those values into another mapping.

Where YAML Is Used