CSV ⇄ JSON

Purpose

CSV and JSON bidirectional converter handling header rows, quote escaping, fields with commas, fields with newlines, empty values, encodings (UTF-8 / GBK), separators (comma/tab/semicolon/pipe). Supports CSV-to-JSON array, JSON array-to-CSV table, flattening nested objects. Common for Excel data into databases, API data exports to Excel, data migration, bulk form filling. All conversion runs locally — sensitive business data does not leave the browser.

Steps

1. Paste CSV or JSON array on the left
2. Tool auto-detects format
3. CSV → JSON: first row is keys, each row is an object, output is an array
4. JSON → CSV: first row keys (merged across all objects), values per row
5. Separator: comma (default), tab, semicolon, pipe, custom
6. Encoding: UTF-8 (default), GBK (legacy Excel files)
7. Nested object: flatten to a.b.c dot path or a_b_c underscore
8. Export: .csv or .json

FAQ

CSV fields with commas?

Per RFC 4180, wrap in double quotes: `"hello, world",foo,bar`. Double quotes inside use two double quotes: `"he said ""hi"""`. Tool handles this. Note: Chinese Excel often exports CSV in GBK — switch charset.

How to flatten JSON nested objects to CSV?

`{"user":{"name":"Tom","age":30}}` flattens to `user.name=Tom, user.age=30` (two columns). Modes: dot path (default), underscore (user_name, user_age), JSON string (one column with the nested object as a JSON string).

What if CSV first row is not a header?

Disable "detect header" — tool uses col_0, col_1, col_2 as keys. Or manually specify a header (comma-separated names in the input box).

Excel opens UTF-8 CSV showing garbled Chinese?

Excel for Windows defaults to GBK and needs a BOM to read UTF-8. Check "include UTF-8 BOM" on export, or export as GBK directly. Newer macOS Excel supports UTF-8 natively.

How are empty fields / null represented?

CSV: consecutive separators (a,,b) for empty. JSON: explicit null. Default conversion: CSV empty → JSON null (clearer); JSON null → CSV empty. Toggle to CSV empty → JSON empty string "" to preserve value type.

Use cases

• Excel data into database: CSV → JSON → bulk insert API
• API data into Excel: JSON data converted to CSV for business teams
• Data migration: legacy DB export CSV → JSON → import to new DB
• Bulk form filling: form JSON data converted to CSV for Excel template
• Data analysis: JSON API data to CSV for Excel / pandas

Use cases

Excel ↔ database/API, data migration, bulk form filling, analysis prep. Backend, data engineering, ops, finance. RFC 4180 standard, nested flattening, Excel BOM, multi-charset are the differentiators.