JSON ⇔ CSV Converter

What is the JSON ⇔ CSV Converter?

The JSON ⇔ CSV Converter is a tool for converting between the JSON format—commonly used in web APIs and programming—and the CSV format—widely used in spreadsheet software and business systems.While JSON can represent structured data using objects and arrays, CSV is a simple tabular format consisting of rows and columns, making it well-suited for importing into Excel or spreadsheets, reviewing list data, and transferring data to other systems.You can use this tool when you want to save JSON retrieved from an API as a CSV file, or when you want to convert CSV list data into JSON that can be processed by JavaScript or an API.

When converting from JSON to CSV, you generally provide an array of objects that all contain the same types of fields.For example, if you have JSON containing multiple product objects with fields such as name, price, and stock, each key becomes a column header in the CSV, and each object is output as a separate row. Even if a field is present in only some rows, all keys are collected to create columns, and cells without values are treated as blank.Nested objects can be expanded into column names such as `address.city` by enabling “Expand nested JSON using dot notation.”

When converting from CSV to JSON, treat the first row as column names and convert the rows starting from the second row into an object. Since all values in CSV are represented as strings, enabling "Infer Types" allows you to convert 123 to a number, true or false to booleans, and null to null.For data where leading zeros are important—such as product codes or ZIP codes—the values must be retained as strings; therefore, it is recommended to turn off type inference for such cases.

CSV delimiters support not only commas but also tabs, semicolons, and pipes. If you select tabs, the file can be used as a TSV file.If a cell contains commas, line breaks, or double quotes, the data is enclosed in double quotes according to standard CSV rules, and any double quotes within the cell are doubled during output. This allows the system to handle data containing text or descriptions that would otherwise be prone to corruption by simple string replacement.

This tool’s conversion process is performed within the browser using JavaScript; it does not upload the entered JSON or CSV files to a server for conversion.Even when handling customer data or internal data, you can avoid sending data to external servers. However, please take separate precautions regarding shared devices, browser extensions, and the security of the device itself. Very large data sets consume a significant amount of browser memory, so please split the data as needed.

Key Features

• You can convert an array of JSON objects to CSV or TSV.
• You can convert CSV and TSV files into an array of JSON objects.
• Supports comma, tab, semicolon, and pipe delimiters.
• You can expand nested JSON objects into dot-notation columns.
• When converting from CSV to JSON, the system can infer the types of numeric values, booleans, and null values.
• You can toggle the formatted display of JSON.
• You can copy the results or save them as CSV, TSV, or JSON files.
• Input data is processed within the browser rather than being sent to the server. Resource-intensive conversions are executed using Web Workers, and the system is designed to minimize interruptions to user interaction even while processing is underway.

How to Use the JSON ⇔ CSV Converter

1. Select the conversion direction from "JSON → CSV" or "CSV → JSON."
2. Paste data into the input field or select a JSON, CSV, or TSV file.
3. Select the necessary settings, such as the CSV delimiter, JSON nesting expansion, and type inference for CSV values.
4. Click "Convert" to display the results. If the results area is off-screen, it will automatically scroll into view.
5. Review the content and use "Copy Results" or "Download."
6. To reduce the load on your device when working with large datasets, enable "Low-Load Mode." While processing is in progress, you can use the progress indicator and the "Pause Processing" button.
7. If you want to convert in the opposite direction, use "Reverse Conversion Direction" to move the result to the input side and continue converting.

Precautions for Use

• JSON → CSV is intended for data that can be converted into a tabular format; it cannot fully represent complex hierarchical arrays.
• When CSV type inference is enabled, values such as 00123 are treated as strings rather than numbers, so values starting with a zero are automatically treated as strings.
• When converting from CSV to JSON, use the first row as the column names. Since duplicate column names will be overwritten by subsequent values, please ensure that column names are unique.
• Since large amounts of data can affect device memory and processing time, please aim to keep the file size under 20 MB.

Frequently Asked Questions About the JSON ⇔ CSV Converter

What kind of JSON should I enter to convert it to CSV?

Generally, you enter an array of objects. Even a single object can be converted into a single line of CSV data.

Can nested JSON also be converted to CSV?

Yes. If you enable "Expand nested JSON using dot notation," you can expand it into column names such as address.city.

What happens to JSON that contains arrays?

Arrays within objects are output as JSON strings so they fit into a single CSV cell. We recommend organizing the structure of complex multidimensional data in advance.

Will the data be converted to numeric values when converting from CSV to JSON?

When type inference is enabled, common numeric values, `true`, `false`, and `null` are converted to their respective JSON types. When disabled, they are all treated as strings.

Can values with leading zeros, such as 00123, be retained?

Yes. Even when type inference is enabled, we ensure that values in integer format with leading zeros are stored as strings.

Does it support TSV as well?

Yes. If you select “Tab (TSV)” as the delimiter, you can convert between JSON and TSV.

Can you convert CSV files that contain commas or line breaks within cells?

As long as the data is enclosed in double quotes according to CSV rules, the system can parse commas, line breaks, and double quotes within the cells.

Are JSON and CSV files sent to the server?

No. File loading and conversion are handled by JavaScript within the browser.

Can I save the translation results as a file?

Yes. Depending on the conversion direction, you can download files in .csv, .tsv, or .json format.

How is the column order in a CSV file determined?

Collect the keys appearing in the JSON in order starting from the first object, and if a new key appears, add it to the end.

Is the first row of the CSV file required?

When converting from CSV to JSON, the first row is used as JSON keys, so a header row containing column names is required.

Can I convert Excel files directly?

This tool supports JSON, CSV, and TSV files. Please save .xlsx files as CSV files before using them.

What should I do if the browser slows down when handling large files?

When Low-Load Mode is enabled, processing is broken down into smaller chunks with pauses in between. Additionally, since conversion processing is executed in a Web Worker, the screen is less likely to freeze, and you can stop the process using the "Interrupt" button while it is running.