Why does yes stay a string in the JSON?

YAML 1.2, the default here, reads only true and false (as true, True or TRUE) as booleans, so yes, no, on and off are text. YAML 1.1 also read those words, plus y and n, as booleans. Tick the YAML 1.1 option to read them that way, or write true and false.

Are anchors, aliases and merge keys supported?

Yes. &name and *name are expanded, and a << merge key copies a mapping in, so a base of x: 1 merged into a mapping with y: 2 gives {"x":1,"y":2}. Expansion stops at 50,000 values and 2,000,000 characters of JSON, which keeps a hostile file from freezing the page.

What happens to a file with several documents?

Documents separated by --- become one JSON array in their order, and a note says so: a: 1, then ---, then b: 2 gives [{"a":1},{"b":2}].

Why did my large number change?

JSON numbers are 64-bit floats, which hold whole numbers exactly only up to 9,007,199,254,740,991. 9007199254740993 comes out as 9007199254740992, and the converter warns about it. Quote IDs and other long numbers in the YAML to keep them as text.

Yes, in this browser’s local storage, so it is still there on your next visit; it is not uploaded. Clear Saved Values removes it and brings back the example.

YAML to JSON Converter

Convert YAML to JSON with anchors and merge keys resolved, YAML 1.2 or 1.1 typing for yes/no, and a warning for numbers JSON cannot hold. How it works

YAML Input

Your YAML is kept in this browser only (local storage) so it is still here next visit; nothing is uploaded. Limit: 100,000 characters. Anchors and merge keys (<<) are resolved, and YAML 1.2 is read by default: yes, no and on stay text.

JSON Output

{
  "name": "John",
  "age": 30,
  "active": true,
  "tags": [
    "dev",
    "ops"
  ]
}

1 document · 6 lines · 4 keys · max depth 2

About the YAML to JSON Converter

In YAML to JSON conversion, true becomes true but yes stays the text "yes", because this converter reads YAML 1.2 by default and YAML 1.2 treats only true and false as booleans. Tick the YAML 1.1 option for files written for older readers: then yes, no, on and off become booleans and 017 is the octal number 15.

How YAML values come out in JSON

YAML value	JSON with YAML 1.2 (default)	JSON with the YAML 1.1 option
yes	"yes"	true
no	"no"	false
on	"on"	true
off	"off"	false
y	"y"	true
NO	"NO"	false
true	true	true
"yes"	"yes"	"yes"
017	17	15
0o17	15	"0o17"
0x1F	31	31
1_000	"1_000"	1000
12:30	"12:30"	750
2024-01-15	"2024-01-15"	"2024-01-15T00:00:00.000Z"
~	null	null
1.10	1.1	1.1
9007199254740993	9007199254740992	9007199254740992
.nan	null	null

Each row is the JSON for a: followed by the value. 12:30 in YAML 1.1 is a base-60 number (12 × 60 + 30). The last two rows come with a warning: 9007199254740993 loses its last digit because JSON numbers are 64-bit floats, and .nan has no JSON form.

Frequently asked questions

Why does yes stay a string in the JSON?: YAML 1.2, the default here, reads only true and false (as true, True or TRUE) as booleans, so yes, no, on and off are text. YAML 1.1 also read those words, plus y and n, as booleans. Tick the YAML 1.1 option to read them that way, or write true and false.
Are anchors, aliases and merge keys supported?: Yes. &name and *name are expanded, and a << merge key copies a mapping in, so a base of x: 1 merged into a mapping with y: 2 gives {"x":1,"y":2}. Expansion stops at 50,000 values and 2,000,000 characters of JSON, which keeps a hostile file from freezing the page.
What happens to a file with several documents?: Documents separated by --- become one JSON array in their order, and a note says so: a: 1, then ---, then b: 2 gives [{"a":1},{"b":2}].
Why did my large number change?: JSON numbers are 64-bit floats, which hold whole numbers exactly only up to 9,007,199,254,740,991. 9007199254740993 comes out as 9007199254740992, and the converter warns about it. Quote IDs and other long numbers in the YAML to keep them as text.
Is my YAML saved?: Yes, in this browser’s local storage, so it is still there on your next visit; it is not uploaded. Clear Saved Values removes it and brings back the example.

Common Use Cases

Developers turn a Kubernetes manifest, a Docker Compose file or a GitHub Actions workflow into JSON to feed an API, a JSON Schema check or jq, or to see exactly what a YAML reader made of the file. Four example files load with one click, a .yaml or .yml file can be uploaded, and the JSON can be copied or downloaded.

How the YAML is read

The text is read with js-yaml under the YAML 1.2 core schema, with anchors, aliases and << merge keys resolved, then printed with JSON.stringify at 2 or 4 spaces, minified or with sorted keys.

Example: active: true becomes "active": true, but enabled: yes becomes "enabled": "yes", because YAML 1.2 reads only true and false as booleans. Tick the YAML 1.1 option and yes, no, on, off, y and n become true or false (as keys too), 017 becomes 15 and dates become ISO text in UTC.

Several --- documents become one JSON array. Whole numbers beyond 9,007,199,254,740,991 are flagged because JSON numbers are 64-bit floats, and .nan or .inf become null with a warning. Input is limited to 100,000 characters, 100 levels of nesting, 50,000 values once aliases are expanded and 2,000,000 characters of JSON.

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