JSON to CSV · Nested Object Flattening · Auto-extract headers
JSON to CSV Converter is an efficient and reliable online format conversion tool designed to convert JSON data into CSV (Comma-Separated Values) format. In data analysis and processing workflows, CSV is one of the most universal data exchange formats — virtually all spreadsheet software (Excel, Google Sheets, Numbers) and database tools natively support CSV import and export. However, modern Web APIs and NoSQL databases typically return data in JSON format, creating a gap that a reliable conversion tool needs to bridge. This tool intelligently handles nested objects, array fields, and special characters, ensuring the converted CSV data is complete, accurate, and easy to use. Whether you're a data analyst cleaning data or a developer preparing test datasets, this tool will save you significant time.
Paste your JSON data into the input area. You can copy data from API responses, log files, database exports, or any JSON data source. The tool supports JSON array format (the most common data list format) and JSON object format. If the data contains nested objects or arrays, the tool automatically flattens them, expanding nested fields into dot-separated column names (e.g., address.city becomes a separate CSV column). After pasting, the tool immediately previews the parsed result, showing the number of detected fields and records.
Configure conversion options. You can customize the delimiter (comma, semicolon, tab, etc.), choose whether to include a header row, set quote wrapping rules (always wrap, wrap only when special characters are present), and control how null values are displayed. For nested data, you can choose a flattening strategy: expand nested objects into multiple columns, or serialize nested data as JSON strings within a single column. These options let you precisely control the output format to meet the requirements of your target system or tool.
Download the converted CSV file. Click the "Convert & Download" button and the tool instantly generates a CSV file and triggers a browser download. After conversion, you can preview the first few rows in the preview area to confirm the results meet your expectations. If adjustments are needed, modify the options and reconvert. The generated CSV file uses UTF-8 encoding, compatible with Excel, Google Sheets, LibreOffice Calc, and all major database import functions. The file size is typically smaller than the original JSON, making it easy to store and transfer.
For nested objects, the tool uses dot notation to flatten nested fields into flat column names by default. For example, {"user": {"name": "Tom", "age": 25}} becomes two columns: user.name and user.age. For array-type fields, the tool offers two approaches: concatenate array elements with commas into a single column, or split the array into multiple rows (similar to database denormalization). You can choose the approach that best fits your needs in the settings panel.
If Chinese characters appear garbled when opening the CSV in Excel, this is due to Excel's incomplete UTF-8 CSV recognition. Several solutions exist: use Excel's "Data → From Text/CSV" import feature to manually specify UTF-8 encoding; open the file in Google Sheets (which natively supports UTF-8); or open it in Notepad and save as UTF-8 with BOM. This tool outputs standard UTF-8 format for maximum compatibility — if you need a BOM version, enable that option in settings.
Can it convert very large JSON files? Since this tool runs in the browser, performance depends on your device. For JSON files under 50MB, modern browsers typically complete the conversion in seconds. For larger files, we recommend filtering or splitting the data before converting. The tool uses streaming processing to optimize memory usage, preventing browser crashes when handling large files. If you frequently need to convert very large datasets, consider a server-side processing solution.