Why does this need inputs instead of input?

It compares two documents, so it reads an "inputs" array rather than a single "input". Send exactly two items; both count together against the size limit.

Does key order count as a difference?

No. Objects are compared by structure, so reordering keys reports nothing. Array order does count, because order is meaningful in a JSON array.

What does a change look like?

Each entry carries a path such as limits.calls, a type of added, removed or changed, and the before and after values. The report also gives counts and an "identical" flag you can branch on.

JSON diff API

Compare two documents and list what was added, removed and changed.

Get a free token Full API reference

Endpoint	POST https://astraljson.com/api/v1/json-compare
Auth	Bearer token, free
Sends	inputs: text[]
Returns	result: json
Price	Free. 1,000 calls a day, 60 a minute.

When to call it

A text diff of two JSON files reports a reformat as a change and a reordered object as a rewrite. This compares the structures, so a test that asserts on an API response, or a job watching a config for real drift, only fires when something actually moved.

For a one-off, the browser version needs no token and never sends your data anywhere: it runs on your own machine.

Example

curl

curl -X POST https://astraljson.com/api/v1/json-compare \
  -H "Authorization: Bearer ast_YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"inputs": ["{\"plan\":\"free\",\"limits\":{\"calls\":100}}","{\"limits\":{\"calls\":1000},\"plan\":\"free\",\"beta\":true}"]}'

response

{
  "tool": "json-compare",
  "result": "{\n  \"identical\": false,\n  \"added\": 1,\n  \"removed\": 0,\n  \"changed\": 1,\n  \"changes\": [\n    {\n      \"path\": \"beta\",\n      \"type\": \"added\",\n      \"after\": true\n    },\n    {\n      \"path\": \"limits.calls\",\n      \"type\": \"changed\",\n      \"before\": 100,\n      \"after\": 1000\n    }\n  ]\n}",
  "chars": 276,
  "ms": 1
}

In your language

JavaScript

const res = await fetch("https://astraljson.com/api/v1/json-compare", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.ASTRAL_TOKEN}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({"inputs": ["{\"plan\":\"free\",\"limits\":{\"calls\":100}}","{\"limits\":{\"calls\":1000},\"plan\":\"free\",\"beta\":true}"]}),
});
if (!res.ok) throw new Error((await res.json()).detail);
const { result } = await res.json();

Python

import os, requests

res = requests.post(
    "https://astraljson.com/api/v1/json-compare",
    headers={"Authorization": f"Bearer {os.environ['ASTRAL_TOKEN']}"},
    json={"inputs": ["{\"plan\":\"free\",\"limits\":{\"calls\":100}}","{\"limits\":{\"calls\":1000},\"plan\":\"free\",\"beta\":true}"]},
    timeout=30,
)
res.raise_for_status()
result = res.json()["result"]

Parameters

Field	Type	Notes
inputs	string[]	Required. Between 2 and 20 items. Up to 200,000 characters per call.

Errors

Errors are RFC 7807 problem documents with a stable type you can branch on.

missing-token	401	No Authorization header.
bad-request	400	inputs missing or the wrong type.
tool-failed	422	The input could not be processed. detail says why.
quota-exceeded	429	Past 1,000 calls today.

Questions

Why does this need inputs instead of input?: It compares two documents, so it reads an "inputs" array rather than a single "input". Send exactly two items; both count together against the size limit.
Does key order count as a difference?: No. Objects are compared by structure, so reordering keys reports nothing. Array order does count, because order is meaningful in a JSON array.
What does a change look like?: Each entry carries a path such as limits.calls, a type of added, removed or changed, and the before and after values. The report also gives counts and an "identical" flag you can branch on.

Other endpoints

A token takes thirty seconds

Free, no card, 1,000 calls a day, and the same token works on astraltext.com, astralpdf.com, astraljson.com and astralbatch.com.

Get a free token