What indentation can I ask for?

Two spaces (the default), four spaces, or a tab. Send "option": "2", "4" or "tab". Anything else is refused with a bad-option error rather than silently falling back.

Does it change my data?

No. It parses the document and prints it again, so whitespace changes and nothing else. Key order is preserved exactly as it arrived.

What happens if the JSON is invalid?

You get a 422 with a message naming the line and column of the first fault, the same message the validator endpoint returns.

JSON formatter API

Pretty-print JSON with two spaces, four spaces or a tab.

Get a free token Full API reference

Endpoint	POST https://astraljson.com/api/v1/json-prettify
Auth	Bearer token, free
Sends	input: text
Returns	result: text
option	2 \| 4 \| tab
Price	Free. 1,000 calls a day, 60 a minute.

When to call it

Formatting in a script is nearly always about making a diff readable. Config files, fixtures and recorded API responses arrive on one line because a machine wrote them, and a human then has to review them. Running every one of them through the same indentation in a pre-commit hook or a CI step is what makes the next diff show the change rather than the reformat.

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-prettify \
  -H "Authorization: Bearer ast_YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"input": "{\"name\":\"astral\",\"tools\":[\"prettify\",\"validate\"],\"free\":true}", "option": "2"}'

response

{
  "tool": "json-prettify",
  "result": "{\n  \"name\": \"astral\",\n  \"tools\": [\n    \"prettify\",\n    \"validate\"\n  ],\n  \"free\": true\n}",
  "chars": 87,
  "ms": 1
}

In your language

JavaScript

const res = await fetch("https://astraljson.com/api/v1/json-prettify", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.ASTRAL_TOKEN}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({"input": "{\"name\":\"astral\",\"tools\":[\"prettify\",\"validate\"],\"free\":true}", "option": "2"}),
});
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-prettify",
    headers={"Authorization": f"Bearer {os.environ['ASTRAL_TOKEN']}"},
    json={"input": "{\"name\":\"astral\",\"tools\":[\"prettify\",\"validate\"],\"free\":true}", "option": "2"},
    timeout=30,
)
res.raise_for_status()
result = res.json()["result"]

Parameters

Field	Type	Notes
input	string	Required. Up to 200,000 characters per call.
option	string	One of: 2, 4, tab.

Errors

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

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

Questions

What indentation can I ask for?: Two spaces (the default), four spaces, or a tab. Send "option": "2", "4" or "tab". Anything else is refused with a bad-option error rather than silently falling back.
Does it change my data?: No. It parses the document and prints it again, so whitespace changes and nothing else. Key order is preserved exactly as it arrived.
What happens if the JSON is invalid?: You get a 422 with a message naming the line and column of the first fault, the same message the validator endpoint returns.

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