Pretty Print JSON — 6 Ways, All Languages

Pretty Printing JSON in JavaScript

JavaScript has built-in support for pretty printing JSON through theJSON.stringify() method. The third argument, called the space parameter, controls indentation:

// Pretty print an object
const data = { name: 'Alice', scores: [98, 87, 92] };
console.log(JSON.stringify(data, null, 2));
// {
//   "name": "Alice",
//   "scores": [
//     98,
//     87,
//     92
//   ]
// }

// Pretty print a raw JSON string (re-format)
const raw = '{"x":1,"y":2}';
console.log(JSON.stringify(JSON.parse(raw), null, 2));

// With tab indentation
console.log(JSON.stringify(data, null, '\t'));

// Pretty print to a file in Node.js
const fs = require('fs');
fs.writeFileSync('output.json', JSON.stringify(data, null, 2));

// Replacer function — filter keys or transform values before pretty printing
const filtered = JSON.stringify(data, (key, value) => {
  if (key === 'privateField') return undefined; // exclude this key
  return value;
}, 2);

Pretty Printing JSON in Python

import json

# Pretty print a Python dict
data = {"name": "Alice", "scores": [98, 87, 92]}
print(json.dumps(data, indent=2))

# Pretty print a JSON string
raw = '{"x":1,"y":2}'
print(json.dumps(json.loads(raw), indent=2))

# Sort keys alphabetically while pretty printing
print(json.dumps(data, indent=2, sort_keys=True))

# Preserve Unicode characters (don't escape to \uXXXX)
data_unicode = {"greeting": "こんにちは", "city": "東京"}
print(json.dumps(data_unicode, indent=2, ensure_ascii=False))

# Read a file, pretty print, write to another file
with open('raw.json') as f:
    data = json.load(f)
with open('pretty.json', 'w') as f:
    json.dump(data, f, indent=2, ensure_ascii=False)

# One-liner from command line:
# python3 -m json.tool raw.json

Pretty Printing JSON from the Command Line

# ── jq (recommended) ──────────────────────────────────────────────────
# Install: brew install jq (Mac), apt install jq (Ubuntu)

# Pretty print a file
jq . data.json

# Pretty print curl response
curl -s https://api.github.com/users/octocat | jq .

# Extract a specific field and pretty print
curl -s https://api.github.com/users/octocat | jq '.login, .name, .public_repos'

# Pretty print with coloured output (jq does this by default in terminal)
jq -C . data.json | less -R

# ── Python (built-in, no install needed) ──────────────────────────────
echo '{"a":1,"b":[2,3]}' | python3 -m json.tool

# From a file
python3 -m json.tool data.json

# To a file
python3 -m json.tool data.json > pretty.json

# ── Node.js ───────────────────────────────────────────────────────────
echo '{"a":1}' | node -e "
let d='';process.stdin.on('data',c=>d+=c);
process.stdin.on('end',()=>console.log(JSON.stringify(JSON.parse(d),null,2)))
"

Pretty Printing JSON in Go

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
)

type User struct {
    Name  string   `json:"name"`
    Score []int    `json:"scores"`
}

func main() {
    // Pretty print a struct
    user := User{Name: "Alice", Score: []int{98, 87, 92}}
    b, err := json.MarshalIndent(user, "", "  ")
    if err != nil {
        panic(err)
    }
    fmt.Println(string(b))

    // Re-format (pretty print) a raw JSON byte slice
    raw := []byte(`{"name":"Bob","scores":[70,80]}`)
    var buf bytes.Buffer
    if err := json.Indent(&buf, raw, "", "  "); err != nil {
        panic(err)
    }
    fmt.Println(buf.String())
}

Pretty Printing JSON in Java

// ── Jackson ───────────────────────────────────────────────────────────
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

ObjectMapper mapper = new ObjectMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT);

// Pretty print an object
String pretty = mapper.writeValueAsString(myObject);

// Re-format a raw JSON string
Object obj = mapper.readValue(rawJsonString, Object.class);
String formatted = mapper.writeValueAsString(obj);

// ── Gson ──────────────────────────────────────────────────────────────
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String pretty = gson.toJson(myObject);

// Re-format a raw JSON string
JsonElement element = JsonParser.parseString(rawJsonString);
String formatted = gson.toJson(element);

Pretty Printing JSON in Rust

// Using serde_json — add to Cargo.toml: serde_json = "1.0"
use serde_json::{json, Value};

fn main() {
    let data = json!({
        "name": "Alice",
        "scores": [98, 87, 92]
    });

    // Pretty print with to_string_pretty
    let pretty = serde_json::to_string_pretty(&data).unwrap();
    println!("{}", pretty);

    // Re-format a raw JSON string
    let raw = r#"{"a":1,"b":[2,3]}"#;
    let v: Value = serde_json::from_str(raw).unwrap();
    println!("{}", serde_json::to_string_pretty(&v).unwrap());
}

Key Facts

JavaScript:

JSON.stringify(obj, null, 2) — third arg is indent

Python:

json.dumps(data, indent=2) — or python3 -m json.tool from CLI

Go:

json.MarshalIndent(v, "", " ") — second arg is prefix, third is indent

Java (Jackson):

mapper.enable(SerializationFeature.INDENT_OUTPUT)

Terminal:

jq . file.json — fastest, most feature-rich

curl:

curl -s URL | jq . — API response debugging

Related Tools

• Format JSON Online — live formatter tool
• JSON Beautifier Online — beautifier-focused guide
• Minify JSON Online — the opposite operation
• JSON Formatter JavaScript — deep-dive on JS JSON APIs
• JSON Diff Tool — compare two JSON documents
• JSON Path Finder — query nested JSON fields