CSV to JSON Converter
Convert CSV files into a clean JSON array, with optional automatic type detection.
CSV is how data arrives from spreadsheets, databases and export tools; JSON is how it is consumed by code. Moving between the two is a constant task for developers, data analysts and anyone wiring an old export into a new API. This converter turns a CSV table into a clean JSON array, using the first row as the object keys.
Paste your CSV and press Convert. The parser handles the fiddly parts of the format - quoted fields, commas inside values, escaped quotes, and line breaks within a cell - so a spreadsheet export converts cleanly instead of shedding rows. The first row becomes the property names, and every following row becomes one object.
By default every cell stays a string, which preserves exactly what the file contains. Toggle "Auto-detect types" to convert recognizable numbers, booleans and null into native JSON values. Processing is local: your data never leaves the browser, which matters for exports that contain customer or payroll records.
Features
- First row becomes JSON keys; each following row becomes an object.
- Robust parser for quoted fields, embedded commas, escaped quotes and newlines in cells.
- Optional auto-detection of numbers, booleans and null for typed JSON.
- Duplicated headers preserved as repeated keys rather than silently dropped.
- Pretty-printed JSON output, two-space indentation, ready to use.
- One-click download as a .json file.
- Fully offline - the CSV is parsed locally and never uploaded.
How to Use
- 1
Paste your CSV
Enter the CSV text, including the header row. Exports from Excel, Sheets and most databases paste directly.
- 2
Enable type detection if you want it
Leave "Auto-detect types" off to keep every cell a string, or enable it to convert 42, true and null into native JSON values.
- 3
Convert
Press Convert to JSON. Each row becomes an object with the header cells as keys.
- 4
Copy or download
Copy the JSON for your code, or download it as a .json file for use elsewhere.
Example
Simple table to JSON
name,role
Ada,Engineer
Linus,Maintainer↓
[
{ "name": "Ada", "role": "Engineer" },
{ "name": "Linus", "role": "Maintainer" }
]Comma inside a quoted field
name,note
Ada,"Loves commas, sometimes"↓
[
{ "name": "Ada", "note": "Loves commas, sometimes" }
]Common Problems
Spaces in the header row
A header like "user name" produces a JSON key "user name". If your downstream code expects clean identifiers, trim or rename headers in the CSV before converting.
Commas inside unquoted fields
If a field contains a comma but the CSV was not quoted, the parser sees an extra column and the row shifts. Most spreadsheets quote such values automatically - exports from Excel and Sheets are safe; hand-typed CSV may not be.
Relying on auto-detection for identity values
A value like "007" or a long product id can be misread as a number and lose formatting. With detection off, everything stays a string - use that mode when identifiers matter more than types.
Line breaks inside cells
A quoted cell can contain a real newline, which a naive line-splitter would cut into a new row. The parser tracks quotes, so multi-line cells stay intact inside a single object.
Windows line endings
Files exported on Windows use CRLF line endings. The parser normalizes both CRLF and bare CR to LF internally, so rows do not split or merge across platforms.
Empty cells becoming missing keys
An empty cell produces a key with an empty-string value, so the output shape stays consistent - every row has every key. That is usually what downstream code expects.
Technical Details
The parser is a small state machine rather than a split-on-comma, so it correctly handles the RFC-4180 rules: a double quote starts quoted mode, and a doubled quote inside a quoted field is an escaped quote.
Newlines are normalized before parsing (CRLF and CR become LF), which makes the tool robust to files exported on Windows.
With type detection enabled, a cell is converted when it fully matches a number, boolean or null pattern; anything else - including values with leading zeros or trailing text - stays a string to avoid corrupting the data.
Header cells are trimmed of surrounding whitespace, and empty header cells still produce a key so column positions are preserved.
Processing is local and synchronous. The CSV never leaves your browser and nothing is stored between sessions.
The parser is intentionally strict about structure but forgiving about whitespace: it never guesses at malformed quoting, so a broken field surfaces as an error instead of silently shifting every later column.
Frequently Asked Questions
Why are my numbers coming out as strings?
Because the default is to preserve exactly what the file contains. Enable "Auto-detect types" to convert clean numbers, booleans and null into native JSON values instead.
How are cells with commas handled?
Correctly, as long as the cell is quoted in the CSV, which spreadsheet exports do automatically. The parser respects quotes, so a value like "Smith, John" stays one field.
What if my CSV has no header row?
The first row is always used as headers. If your file has no header row, add one first, or the first data row will become the keys - which is rarely what you want.
Can I convert an Excel file directly?
Not a .xlsx binary - this tool reads CSV text. In Excel use Save As → CSV, or copy-paste the cells as comma-separated values, then convert here.
Is my data uploaded?
No. Parsing and conversion happen entirely in your browser. The CSV is processed in memory and never transmitted, stored or logged.
Why do duplicated headers both appear in the output?
JSON objects cannot hold two identical keys, so the converter preserves both columns by using the same key twice rather than dropping data. Many parsers silently discard one - this tool keeps the information.
What happens if a field contains a double quote?
A doubled quote inside a quoted CSV field is the standard escape, and the parser resolves it back to a single quote in the JSON value. The data round-trips exactly as the spreadsheet wrote it.
Does order matter in the output?
Yes - rows keep their original order and object keys keep the header order. Nothing is re-sorted, so the JSON preserves the source sequence exactly.
Data & Privacy
Your data stays in your browser. Nothing is uploaded.
- Processing
- Local
- Upload
- None
- Server Storage
- None
- Account
- Not required
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