How to use the CSV to JSON Converter
- Choose a conversion direction: CSV → JSON or JSON → CSV.
- Paste your data into the input box, or click Open file to load a .csv, .tsv or .json file. Older CSV files saved by Excel in the Windows-1252 (Western ANSI) encoding are detected automatically.
- Auto-detect usually picks the right delimiter. If the first row doesn't contain column names, uncheck "First row is a header."
- Click Convert, then copy the result or save it as a file. CSV is saved as UTF-8 with a BOM so accented letters and symbols display correctly in Excel.
What does CSV look like after converting to JSON?
When the first row is used as a header, each row becomes an object of "column name": value pairs, and the whole file becomes an array of objects.
| CSV | JSON result |
|---|---|
Name,AgeJohn Smith,31 | [{"Name": "John Smith", "Age": 31}] |
With automatic conversion turned on, cells that contain only a number, such as 31, become JSON numbers, and true and false become booleans. However, values that start with 0 (ZIP codes like 02134, UK mobile numbers like 07700…, account or product codes) are kept as strings so the leading zero isn't lost. A column with an empty header gets a name like "Column 3", and if the same header appears twice, the second one gets _2 added to the end.
If you turn the header option off, each row becomes a plain array of values instead of an object.
Rules for converting JSON to CSV (Excel)
- For an array of objects, every key found in any object is collected and used as a column header. If an object lacks a key, that cell is left blank.
- Objects nested one level deep are flattened into dotted columns such as
Address.City. Deeper values and arrays are placed in a single cell as a JSON string. - An array of arrays (
[[1,2],[3,4]]) is copied straight into rows and columns, without a header row. - Values containing commas, double quotes or line breaks are wrapped in double quotes, and any quotes inside are doubled, following RFC 4180. Excel and Google Sheets read this format exactly as intended.
Fixing garbled characters when opening CSV in Excel
When Excel opens a UTF-8 CSV file that has no BOM (an invisible marker at the start of the file), it often shows accented letters, currency symbols and other special characters as gibberish, for example é instead of é or £ instead of £. CSV files saved from Tooljip include a UTF-8 BOM, so they display correctly even when you just double-click to open them.
Going the other way, files saved from Excel with the plain "CSV (Comma delimited)" option on Windows are usually encoded in Windows-1252 (Western European ANSI). When you open a file, this tool first tries UTF-8 and, if the file isn't valid UTF-8, automatically reads it as Windows-1252, so characters like é, ñ, ü and £ come through intact. The detected encoding is shown in the status line. Even so, saving as "CSV UTF-8 (Comma delimited)" in Excel is the safest choice for sharing data. If you need to change a text file's encoding itself, use the text encoding converter.
If Excel turns long numbers into something like 1.23E+11 or drops leading zeros, that's not a problem with the CSV file. Excel reformats values automatically when it opens them. To keep such columns as they are, use Data > From Text/CSV in Excel and set those columns to the Text format during import.