SmartQueryTools

Convert CSV to JSON Online

Convert CSV files to JSON format directly in your browser. No upload required — your data never leaves your device.

About converting CSV to JSON

People convert CSV to JSON when tabular data has to feed code rather than a spreadsheet. A JavaScript front end, a test fixture, a static site generator or a document database all expect records with named fields, not rows of positional values. The output here is one JSON array, with one object per CSV row and the header names as keys.

Common sources are spreadsheet exports, CRM and e-commerce reports, and database dumps. Common destinations are fetch() calls in a web app, seed scripts for MongoDB or Firestore, and mock API responses. Because the whole file is a single array, most consumers parse it in one go. That suits files up to tens of megabytes. For larger files, or for processing one record at a time, CSV to NDJSON is the better choice.

The main pitfall is typing. CSV has no types, so each column is inferred, and the JSON keeps those decisions. A column holding 1.50 and 2.00 becomes the numbers 1.5 and 2. A column of yes/no or T/F values becomes true/false. Codes with leading zeros, such as 00123, stay strings. But a single "NA" or "1,200" turns its whole column into strings. Check a few records before you send the file to an API that validates types.

Not sure which format you need? Read the JSON vs CSV comparison.

Worked example

A small orders export with an ID, a customer name, a date, an amount (one missing) and a true/false flag, converted with the default settings.

Input (CSV)

order_id,customer,order_date,amount,shipped
1001,Acme Ltd,2026-03-02,249.5,true
1002,Brightside Co,2026-03-02,1200,false
1003,Acme Ltd,2026-03-05,89.99,true
1004,Northwind,2026-03-07,,false

Output (JSON)

[
  {
    "order_id": 1001,
    "customer": "Acme Ltd",
    "order_date": "2026-03-02",
    "amount": 249.5,
    "shipped": true
  },
  {
    "order_id": 1002,
    "customer": "Brightside Co",
    "order_date": "2026-03-02",
    "amount": 1200,
    "shipped": false
  },
  {
    "order_id": 1003,
    "customer": "Acme Ltd",
    "order_date": "2026-03-05",
    "amount": 89.99,
    "shipped": true
  },
  {
    "order_id": 1004,
    "customer": "Northwind",
    "order_date": "2026-03-07",
    "amount": null,
    "shipped": false
  }
]

What changes when you convert CSV to JSON

  • Each CSV row becomes one object in a top-level array. The header row supplies the keys, in the same order.
  • Numbers are written unquoted: order_id 1001 and amount 249.5 are JSON numbers, not strings.
  • Empty fields become null. In the example, order 1004 has "amount": null.
  • true/false text becomes JSON booleans, as in the shipped field.
  • Dates stay strings in ISO form ("2026-03-02"), because JSON has no date type. Date-times are written as "2026-03-02 10:15:00", with a space instead of a T.
  • Whole numbers above 9,007,199,254,740,991 are written as strings, so no digits are lost when JavaScript parses them.

Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.

Frequently Asked Questions

Can I get nested JSON from a flat CSV?

Not from this converter. Every object has the same flat keys as the CSV header. To build nested objects, for example line items grouped under each order, load the CSV in the SQL Query tool, write a GROUP BY query with struct_pack() and list(), and export the result as JSON.

How do I import the JSON output into MongoDB?

Run mongoimport with the --jsonArray flag, because the file is one array rather than one document per line. Without the flag, mongoimport expects NDJSON. Dates arrive as strings, so convert them with $dateFromString in an update if you need BSON dates.

Why are my 18-digit IDs quoted strings in the JSON?

JavaScript numbers are exact only up to 9,007,199,254,740,991. Larger integers are written as strings so every digit survives. Treat those IDs as strings in your code; parsing them as numbers would round them.

What is JSON format?

JSON (JavaScript Object Notation) is a lightweight, human-readable format that supports nested structures, making it ideal for APIs and document-oriented data.

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