JSON to YAML

This free JSON to YAML converter turns JSON into YAML entirely in your browser. Paste your JSON or upload a .json file, choose how strict the quoting should be, read the output, and download a .yaml file. Nothing leaves your device, and there is no sign-up.

Converting JSON to YAML looks like a formatting job, but the one thing that actually breaks data is quoting. Write yes unquoted and a YAML 1.1 reader hands you back a boolean. Write 007 unquoted and you get the number 7. Write 2001-12-14 unquoted and a YAML 1.1 reader hands you back a date instead of a string. None of those round-trip. This page decides quoting against a named resolver — YAML 1.2 core schema or YAML 1.1, your choice — and then lists every value it quoted together with the rule that forced it.

How to use this JSON to YAML converter

• Paste your JSON into the box, or upload a .json or .txt file.
• Pick the Indent width — 2 or 4 spaces per level.
• Pick Read back as: YAML 1.2 (core schema) or YAML 1.1. This is the version whose rules decide whether a value is ambiguous. If you do not know which one will read your file, choose YAML 1.1 — it treats more values as ambiguous, so it quotes more and is the safer default.
• Choose Null as (null, ~, or an empty value) and Line breaks (literal block scalar, or escaped \n inside double quotes).
• Click Convert to YAML, open Why these values are quoted to check the decisions, then Download .yaml.

What this tool supports

Quoting: when a value must be quoted

A plain (unquoted) YAML scalar is not always a string. Every YAML processor matches it against a list of regular expressions first, and whatever matches wins. Two rules follow from that, and this page applies both:

• Ambiguity. If a string would be resolved to null, bool, int, float or (under YAML 1.1) timestamp, it is quoted, because reading it back would not give you the string you started with.
• Structure. If a string cannot be written as a plain scalar at all — it starts with an indicator character such as #, [, - followed by a space, or !; or it contains ": " or " #"; or it has leading or trailing whitespace, which plain scalars drop — it is quoted too.

The resolvers are transcribed from the specifications: the YAML 1.2.2 specification, section 10.3.2 (Core Schema, Tag Resolution), and the YAML 1.1 type definitions for bool, int, float, null and timestamp. The structural rules come from the plain-scalar productions of the YAML 1.2.2 specification. Here is what that means for real values:

Keys are checked with the same rules. A JSON key such as "true", "007" or "yes" is quoted as well, because an unquoted key is resolved by the very same list of regular expressions.

Indentation

Two or four spaces per level. Sequences are written with the classic - prefix and their contents indented one level, so a list of objects comes out as - id: 1 followed by the remaining keys aligned under id.

Nulls, empty objects and empty arrays

• Null can be written as null, as ~, or as an empty value (key: with nothing after the colon). All three read back as null; pick the one your project's style expects.
• Empty object becomes {} and empty array becomes [], written inline on the same line as the key. Both are flow collections, and both read back as an empty map and an empty sequence rather than as null.

Multi-line strings

By default a string containing line breaks is written as a literal block scalar: the key is followed by |, |- or |+, and the text follows on indented lines. |- means no trailing newline, | means one trailing newline, and |+ means every trailing newline is kept — the page picks the header from your actual string so the value round-trips. Switch Line breaks to Escaped and the same string is written on one line with \n inside double quotes instead.

A block scalar cannot preserve trailing spaces on a line or leading indentation on its first line. When your string has either, the page falls back to the escaped form and says so in the explanation list, instead of silently losing those characters.

Numbers and key order

• Numbers keep their original text. 1.0 stays 1.0 and is not rewritten to 1.
• JSON writes exponents as 1e5, but the YAML 1.2 core schema requires a signed exponent and YAML 1.1 additionally requires a . in a float. Left alone, 1e5 would come back as the string "1e5". This page rewrites it to 1.0e+5 so it still reads back as a number, and reports the rewrite.
• Key order is preserved exactly. The JSON is read by a parser written for this page rather than by JSON.parse, because JavaScript objects reorder keys that look like array indexes — {"2":…, "1":…} would otherwise come out swapped.

Privacy

Uploaded files are read with the browser's own file reader and never leave your device. There is no upload endpoint on this page, no account, and no stored history. You can disconnect from the internet after the page loads and it will still work.

What this tool does not do

• Comments are not preserved, because JSON has no comments. A // or /* */ inside your input is not valid JSON, so this page rejects it rather than pretending to carry anything over into the YAML output. If you need comments in the result, add them after converting.
• Duplicate keys collapse. JSON does not define what {"a":1,"a":2} means; this page keeps the last value, keeps the first key's position, and tells you how many duplicates it collapsed.
• Anchors, aliases, tags and merge keys are never produced. Output is plain block YAML only.
• One input, one output. No batch conversion, no login, no history.

FAQ