JSON to CSV

RFC 4180 Compliant Escaping

The converter follows the RFC 4180 standard for CSV formatting, ensuring compatibility with Excel, Google Sheets, and all major CSV parsers.

// Escaping rules applied:
// 1. Fields containing commas, double quotes, or newlines are wrapped in double quotes
// 2. Internal double quotes are doubled ("" → """)

// Example transformations:
"hello"           → hello
"hello, world"    → "hello, world"
"he said "hi""  → "he said ""hi"""
"line1
line2"    → "line1
line2"

Privacy-First Processing

All JSON parsing, CSV generation, and file downloads happen entirely in your browser. No data is ever sent to a server.

• JSON input never leaves your device
• Generated CSV is created client-side
• File downloads use browser Blob APIs
• Works completely offline after initial load

Input Requirements

The tool expects a JSON array of objects. Each object becomes a row; keys become column headers.

// Valid input (array of objects):
[
  {"id": 1, "name": "Alice", "email": "alice@example.com"},
  {"id": 2, "name": "Bob", "email": "bob@example.com"}
]

// Invalid inputs:
{"id": 1, "name": "Alice"}        // Object, not array
[1, 2, 3]                         // Array of primitives
"not json at all"                 // String

Missing Value Handling

When objects in the array have different keys, missing values are filled with a customizable placeholder.

// Input:
[
  {"id": 1, "name": "Alice", "role": "admin"},
  {"id": 2, "name": "Bob"}  // missing "role"
]

// With missing value = "N/A":
id,name,role
1,Alice,admin
2,Bob,N/A

// With empty missing value (default):
id,name,role
1,Alice,admin
2,Bob,

Dot Notation Parsing

When Flatten nested objects is enabled, one-level nested objects are flattened using dot notation (e.g., address.city). Arrays are never flattened — they are JSON-stringified as a single cell.

// Input with nested object:
[
  {
    "id": 1,
    "name": "Alice",
    "address": {
      "city": "Paris",
      "zip": 75001
    },
    "tags": ["admin", "user"]
  }
]

// With flatten=true:
id,name,address.city,address.zip,tags
1,Alice,Paris,75001,"["admin","user"]"

  // Note: tags array is JSON-stringified, not flattened

Flatten Off (Default)

Nested objects and arrays are JSON-stringified as single cells, preserving structure for downstream parsing.

// Same input, flatten=false (default):
id,name,address,tags
1,Alice,"{"city":"Paris","zip":75001}","["admin","user"]"

  // Both address and tags are JSON-stringified

Deep Nesting Behavior

Only one level of plain objects is flattened. Deeper nesting remains JSON-stringified. Null values use the missing-value placeholder.

// Input with deeper nesting:
{
  "id": 1,
  "user": {
    "profile": {
      "name": "Alice",
      "settings": { "theme": "dark" }
    }
  }
}

// With flatten=true:
id,user.profile.name,user.profile.settings
1,Alice,"{"theme":"dark"}"

  // user.profile.settings is stringified (2+ levels deep)
  // user.profile.name is flattened (1 level)

Programmatic Usage

The core engine is available as a standalone ES module for use in your own projects.

import { convertJsonToCsv } from './engine.js';

const data = [
  { id: 1, user: { name: 'Alice', age: 30 } },
  { id: 2, user: { name: 'Bob', age: 25 } }
];

const result = convertJsonToCsv(data, { flatten: true });
if (result.success) {
  console.log(result.csv);
  // id,user.name,user.age
  // 1,Alice,30
  // 2,Bob,25
}