JSON ↔ YAML Converter

Paste JSON or YAML: the other side updates as you type. 100 % local processing in your browser: no data is sent to a server.

Indentation

2 spaces

4 spaces

JSON

Source

YAML

Result

Learn more about JSON and YAML conversion

What is this tool?

JSON and YAML are two text formats used to describe structured data: objects (key / value pairs), lists, strings, numbers and booleans. JSON relies on braces, brackets and quotes, whereas YAML uses indentation and is designed to be easy to read and write by hand.

This tool converts JSON to YAML, or YAML to JSON, as you type. The area you edit is the source and the other one shows the result. If the source is invalid, the parser error is displayed and the previous result stays in place.

Typical use cases

Writing a configuration file for Docker Compose, Kubernetes, GitHub Actions or GitLab CI from existing JSON data.
Turning a YAML file into JSON to process it with a tool or an API that only accepts JSON.
Converting an OpenAPI (Swagger) specification from one format to the other.
Checking how a YAML file is actually interpreted, by looking at its JSON equivalent.

How to use it

Paste your JSON into the left area, or your YAML into the right area. The other area updates on its own.
The area you are editing is marked as the source. Editing the result turns it into the new source.
Choose the indentation, 2 or 4 spaces. The result is regenerated with that indentation.
Click the Copy button above the area you want to copy to the clipboard.

The conversion is performed by a JavaScript library running in your browser. Nothing is sent to a server, so the tool can be used with confidential configuration files.

Before / after examples

JSON to YAML (2 spaces)

Before

{"name":"DTK","version":"1.0","tools":[{"id":1,"label":"JSON Formatter"}],"active":true}

After

name: DTK
version: "1.0"
tools:
  - id: 1
    label: JSON Formatter
active: true

YAML to JSON (2 spaces)

Before

# Server configuration
server:
  host: localhost
  port: 8080
  debug: false

After

{
  "server": {
    "host": "localhost",
    "port": 8080,
    "debug": false
  }
}

In the first example, "1.0" stays quoted in YAML: without quotes, it would be read as the number 1 . In the second example, the comment disappears, because JSON has no comment syntax.

Common YAML mistakes

YAML is permissive in appearance, but its rules on indentation and special characters are strict. The following mistakes are the most frequent.

Indentation with tabs

Invalid

server:
	host: localhost

Valid

server:
  host: localhost

Missing space after the colon

Invalid

name:DTK

Valid

name: DTK

Unquoted value containing ": "

Invalid

message: Error: file not found

Valid

message: "Error: file not found"

Strings that look like numbers

Invalid

version: 1.10

Valid

version: "1.10"

Some of these mistakes do not trigger any error: name:DTK is read as a single string, and 1.10 as the number 1.1 . Converting the YAML to JSON is a quick way to check how it is really interpreted.

Good to know

The tool follows the YAML 1.2 specification (core schema). Only true and false are booleans: values such as yes , no or on are kept as strings.
A JSON document is technically valid YAML 1.2. Pasted into the YAML area, it is rejected: the status says invalid YAML and asks you to use the JSON area instead.
YAML comments are lost when converting to JSON, and cannot be recovered when converting back.
Anchors ( & ) and aliases ( * ) are resolved: the referenced value is copied at each place where it is used.
A YAML file containing several documents separated by --- cannot be converted to a single JSON document and triggers an error.
The special values .inf and .nan do not exist in JSON and are converted to null .
The order of keys is preserved in both directions.

Alias resolution example

base: &port 8080
api: *port
→ {"base": 8080, "api": 8080}

Did you know?

YAML originally stood for "Yet Another Markup Language". It was later renamed to the recursive acronym "YAML Ain't Markup Language", to stress that it is a data format and not a document markup language.
YAML was first proposed in 2001 by Clark Evans, and designed together with Ingy döt Net and Oren Ben-Kiki.
Since version 1.2, published in 2009, YAML is designed as a superset of JSON: almost any valid JSON document is also a valid YAML document.
In YAML 1.1, the value no is a boolean. Lists of country codes therefore turned Norway ( NO ) into false : this is known as the "Norway problem", and one of the reasons why YAML 1.2 restricted booleans to true and false .
The official YAML website recommends the .yaml file extension, although .yml remains very common.

Frequently asked questions

Is my data sent to a server?: No. All processing is performed locally by your browser. The content is neither stored nor transmitted.
Is the conversion lossless?: The data itself is preserved. However, some YAML features have no JSON equivalent: comments, anchors and the choice of quoting style are lost when converting YAML to JSON.
How do I convert a file with several YAML documents?: Convert each document separately, by pasting the content located between two --- separators.
My file was written for YAML 1.1. Will it be interpreted the same way?: In most cases, yes. The main differences concern booleans ( yes , no , on , off ) and numbers written with a leading zero, which YAML 1.1 reads as octal. Check the JSON result if your file relies on these values.