How to Format and Pretty-Print JSON (Browser, Code and Command Line)

Whitespace between JSON tokens has no meaning. These two documents describe exactly the same data:

{"id":42,"name":"Asha","tags":["admin","beta"],"address":{"city":"Pune","zip":"411001"}}

{
  "id": 42,
  "name": "Asha",
  "tags": [
    "admin",
    "beta"
  ],
  "address": {
    "city": "Pune",
    "zip": "411001"
  }
}

A formatter only touches whitespace. The keys, values and their order should come out exactly as they went in. If a tool reorders keys or changes values while it formats, treat that as a bug, or as a different operation such as sorting.

For a quick one-off job, paste the text into an online editor and run its pretty-print command. A good editor also validates as it formats, so a missing comma or quote is reported instead of silently producing nothing. With TrueJson you paste into the editor and use Pretty Print on the Format ribbon; the Minify command does the reverse.

Browser tools are convenient, but think before pasting production secrets, access tokens or personal data into any website. Editors that process your text locally in the browser are safer than ones that send it to a server, and a quick look at the network tab of your browser's developer tools will tell you which kind you are using.

Every mainstream language can parse JSON and write it back with indentation.

JavaScript and TypeScript

const text = '{"id":42,"name":"Asha","tags":["admin","beta"]}';
const data = JSON.parse(text);

// The third argument is the indentation: a number of spaces, or a string such as "\t"
console.log(JSON.stringify(data, null, 2));

Python

import json

text = '{"id": 42, "name": "Asha", "tags": ["admin", "beta"]}'
data = json.loads(text)

print(json.dumps(data, indent=2, ensure_ascii=False))

Java (Jackson)

ObjectMapper mapper = new ObjectMapper();
JsonNode tree = mapper.readTree(text);
String pretty = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(tree);

C# (System.Text.Json)

using System.Text.Json;

var doc = JsonDocument.Parse(text);
var options = new JsonSerializerOptions { WriteIndented = true };
string pretty = JsonSerializer.Serialize(doc.RootElement, options);

The command line is the fastest option for files and for the output of other commands, such as an API call.

# jq: the most popular tool, "." means "the whole document"
jq . data.json

# Pipe an API response straight into it
curl -s https://api.example.com/users/42 | jq .

# Python's standard library works anywhere Python is installed
python -m json.tool data.json

# Write the formatted result to a new file
jq . data.json > data.pretty.json

jq -S . additionally sorts object keys alphabetically, which is useful before comparing two files. See the guide on sorting JSON for why that matters.

The most important rule is consistency. If configuration files are committed to version control, agree on one style and let a formatter apply it automatically, so that diffs show real changes and not whitespace noise.

Many formatters work by parsing the text into objects and writing it back out. In JavaScript that means numbers become 64-bit floating point values, which can only represent integers exactly up to 9,007,199,254,740,991 (that is Number.MAX_SAFE_INTEGER). Larger integers, such as the 64-bit identifiers used by many databases and social networks, are silently rounded:

const text = '{"orderId": 12345678901234567890}';
console.log(JSON.stringify(JSON.parse(text)));
// {"orderId":12345678901234567000}   <- the last digits changed

Parse-based formatters cannot format text that is not valid JSON, because they cannot parse it. They will report an error, usually with a line and column. Fix the syntax first. The most common causes are trailing commas, single quotes, unquoted keys and comments, all covered in our guide to common JSON errors.