YAML to JSON converter

Q: Are YAML anchors preserved in JSON?

No. Anchors and aliases are resolved into ordinary JSON values because JSON has no anchor reference syntax.

Q: Do YAML comments appear in the JSON output?

No. Comments are lost during conversion. Copy them into separate documentation if they need to survive.

Q: Does yes become true?

No. Under YAML 1.2 semantics, yes and no are strings. Only true and false become booleans.

YAML to JSON runs through our table engine, resolving anchors and aliases while writing JSON-safe values.

Converted with Table engine · nothing stored
Free: 5 conversions a day · 5 MB each
Higher limits →

From real runs

What you get — and what changes

Element	Result	What happens
Mappings and sequences	Kept	YAML objects and lists become JSON objects and arrays with the same data shape.
Anchors and aliases	Changed	Anchors and aliases are resolved so the JSON contains repeated concrete values instead of YAML references.
Comments	Lost	Comments are discarded because JSON has no standard comment syntax.
Multi-document YAML	Changed	A stream separated by --- becomes a JSON array of documents in order.
Dates	Changed	Date-looking values are emitted as strings to avoid timezone surprises in JSON consumers.
YAML 1.2 booleans	Changed	true and false become booleans; yes and no stay strings under YAML 1.2 semantics.
Tags	Lost	Custom YAML tags are not preserved as executable constructors in the JSON output.

Mappings and sequences Kept
YAML objects and lists become JSON objects and arrays with the same data shape.
Anchors and aliases Changed
Anchors and aliases are resolved so the JSON contains repeated concrete values instead of YAML references.
Comments Lost
Comments are discarded because JSON has no standard comment syntax.
Multi-document YAML Changed
A stream separated by --- becomes a JSON array of documents in order.
Dates Changed
Date-looking values are emitted as strings to avoid timezone surprises in JSON consumers.
YAML 1.2 booleans Changed
true and false become booleans; yes and no stay strings under YAML 1.2 semantics.
Tags Lost
Custom YAML tags are not preserved as executable constructors in the JSON output.

Sample conversions

Anchored deployment config

Input: YAML: defaults: &defaults {retries: 3, region: us-east}\njob: {<<: *defaults, name: import}
Output: JSON resolves the alias: {"defaults":{"retries":3,"region":"us-east"},"job":{"retries":3,"region":"us-east","name":"import"}}.

Multi-document stream

Input: ---\nname: first\n---\nname: second\nactive: true
Output: JSON: [{"name":"first"},{"name":"second","active":true}].

YAML 1.2 booleans

Input: YAML: answer: yes\nflag: true\ndate: 2026-09-10
Output: JSON: {"answer":"yes","flag":true,"date":"2026-09-10"}; yes is not a boolean.

A real YAML → JSON run

We converted our YAML sample (423 B) with Table engine on 2026-09-11. It took 1 ms and produced a 558 B JSON file, 1.3× larger than the input. The engine raised no warnings.

Input · sample.yaml · 423 B

4 list items, 0 top-level keys, 20 lines

List items: 4
Top-level keys: 0
Lines: 20

Output · sample.json · 558 B

Array of 4 objects; keys: company, stage, arr, owner, close_date

Records: 4
Keys: company, stage, arr, owner, close_date

First lines of the output

json

[
  {
    "company": "Northwind Traders",
    "stage": "Proposal",
    "arr": 48000,
    "owner": "R. Ayers",
    "close_date": "2026-10-14"
  },
  {
    "company": "Contoso Ltd",
    "stage": "Negotiation",
    "arr": 120000,
    "owner": "P. Ng",
    "close_date": "2026-09-30"
  },
  {
    "company": "Fabrikam",
    "stage": "Qualified",
…

Options and when to change them

multiDocument: Keep the default array output for YAML streams; reject multi-doc input only when your API expects one JSON object.
pretty: Pretty-print for review and code commits; compact output when payload size matters.
schema: Use YAML 1.2 semantics so yes/no stay strings; do not assume older YAML 1.1 booleans.

Do it yourself

bash

yq -o=json '.' in.yaml > out.json

Check your yq implementation and version; Python yq and mikefarah/yq use different flags.

Python PyYAML

bash

python - <<'PY'
import json
import yaml
with open("in.yaml", encoding="utf-8") as fh:
    docs = list(yaml.safe_load_all(fh))
out = docs[0] if len(docs) == 1 else docs
with open("out.json", "w", encoding="utf-8") as fh:
    json.dump(out, fh, indent=2, ensure_ascii=False, default=str)
PY

PyYAML's scalar semantics may differ from strict YAML 1.2; verify yes/no and dates.

YAML to JSON by API or MCP

The HTTP API and the MCP server run the exact engine this page uses (Table engine); the response carries the same warnings the web converter shows. Check support first with GET /api/v1/pairs?from=yaml&to=json.

curl

curl -X POST https://filetypeconverters.com/api/v1/convert \
  -H "Authorization: Bearer $FTC_API_KEY" \
  -F "file=@input.yaml" -F "from=yaml" -F "to=json" \
  -F 'options={"encoding":"utf-8"}' \
  --output output.json

Options this engine accepts for YAML → JSON

Key	Applies to	Type	Default
encoding	Reading YAML	utf-8 · latin1	utf-8
flattenSeparator	Reading YAML	string	.
arrayMode	Reading YAML	json · explode	json
delimiter	Writing JSON	string	,
newline	Writing JSON	·
sheetName	Writing JSON	string
dialect	Writing JSON	postgres · mysql · sqlite	postgres
tableName	Writing JSON	string	data
createTable	Writing JSON	boolean	true

API reference

When this is the wrong conversion

Do not convert YAML to JSON if comments are the important documentation; JSON will drop them.
If custom YAML tags drive application behavior, use your application's YAML parser instead of a generic converter.
For Kubernetes patches where anchors are not accepted anyway, validate the resulting JSON against the target schema.

YAML to JSON questions

Are YAML anchors preserved in JSON?