Convert CSV to JSON Online Free — No Upload, Data Intact
Turn CSV, TSV and text files into clean JSON right in your browser — comma, semicolon and tab delimiters detected automatically, headers become keys. No upload, no signup, no limits.
Drop .csv, .tsv or .txt files here, or click to browse
Supports .csv / .tsv / .txt · processed locally · never uploaded
How to Convert CSV to JSON Online
- Drop one or more .csv, .tsv or .txt files — everything is processed locally and never uploaded.
- Click Convert to JSON — the delimiter is sniffed automatically and rows become objects.
- Check the preview — each result shows the converted table and the first 2,000 characters of JSON.
- Download the result — a single file downloads directly; multiple files come back as a ZIP.
How the Parsing Works
The parser sniffs the delimiter — comma, semicolon or tab — so exports from Excel, European spreadsheets and database tools all work without configuration. Quoted fields are handled per RFC 4180: commas, doubled quotes and even line breaks inside quotes are preserved exactly, and a leading UTF-8 BOM is removed before reading.
The first row supplies the keys, and every following row becomes a JSON object. Missing cells are filled with null so all rows share the same shape. Values are typed the way spreadsheets do it: numeric-looking fields become numbers, TRUE/FALSE keywords become booleans, and date-like values are recognized as Excel serial numbers.
The first row is always treated as the header. If your file starts directly with data, add a header row first — otherwise the first record will be consumed as column names.
What Each CSV Value Becomes in JSON
| Value in the file | JSON value | Notes |
|---|---|---|
| 42 / 3.14 | number | Numeric-looking fields are converted, quoted or not |
| TRUE / FALSE | boolean | Spreadsheet truth keywords are recognized |
| 2020-01-15 | number | Date-like values become Excel serial numbers |
| Empty field | null | Filled in for every column so rows stay uniform |
| "text, with comma" | string | Quoted commas, doubled quotes and embedded line breaks are preserved |
CSV and JSON, Side by Side
| CSV | JSON | |
|---|---|---|
| Structure | Flat grid, header row optional | Named keys on every row |
| Types | Everything is text until a tool guesses | Numbers, booleans and null are explicit |
| Quoting | RFC 4180 escaping, easy to get wrong by hand | No delimiter conflicts |
| Best for | Spreadsheets, bulk exports, mail merge | APIs, scripts, configuration, databases |
Privacy and Limitations
- Files never leave your device — parsing happens in JavaScript inside your browser.
- A CSV file has no sheet structure, so the result is always a single top-level JSON array.
- The first row is always interpreted as the header; there is no headerless mode.
- Very large files are limited by the memory of one browser tab, since everything is processed locally.
Frequently Asked Questions
Is this CSV to JSON converter free?
Yes — 100% free with no sign-up, no watermark and no file limit. All conversion happens locally in your browser.
Which delimiters are supported?
Comma, semicolon and tab are detected automatically, so standard English CSV, European semicolon exports and TSV all convert without settings.
How are commas and quotes inside fields handled?
Per RFC 4180: fields wrapped in double quotes may contain commas, doubled quotes and even line breaks, and all of them survive into the JSON exactly as written.
What if my CSV has no header row?
The first row is always used as the header, so add a header line before converting — otherwise the first data record becomes the column names.
Why does a date turn into a number?
Date-like values are recognized the way Excel recognizes them and stored as serial numbers (days since the end of 1899). Format them in your code, or keep them as text by quoting is not an option — spreadsheet typing applies to every field.
Will my file be uploaded to a server?
No. The file is read and parsed by JavaScript in your browser; your data never leaves your device.
Can I turn JSON back into CSV?
Yes. Use our JSON to CSV converter — each sheet or array becomes a CSV file with UTF-8 BOM so Excel opens it correctly.
Related Tools
Need to view or edit the table after converting?
Open the free online Excel editor