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CSV to JSON Converter
Convert CSV to JSON online — free and unlimited. No sign-up, no limits. Upload your CSV file and download JSON instantly.
Upload your CSV file
Drag & drop or click to browse · Max 500 MB
How to convert CSV to JSON
Upload your file
Drag & drop or click to browse. Supports files up to 500 MB.
Adjust settings if needed
Schema and types are detected automatically — no configuration required.
Preview & download
Inspect the first rows in your browser, then download the converted file — free.
About converting CSV to JSON
The naive way to do this is to read every row into a list of dictionaries and serialise the whole thing at once. That works on a sample file and falls over on a real export: a large CSV expands substantially as JSON, and holding the parsed rows and the encoded string in memory at the same time needs several gigabytes.
This converter streams instead. Rows are read in batches and written as they go, so peak memory depends on the batch size, not on the file — and the progress bar moves throughout rather than jumping from 10% to 100% with nothing in between.
The output is an array of objects keyed by the header row, which is the shape almost every API, config loader and JavaScript consumer expects. Encoding is UTF-8 and the input is decoded tolerantly, so an export from a Windows spreadsheet does not fail on its first accented character.
What actually changes
- Streaming
- Rows are read and written in batches, so peak memory is a function of the batch size rather than the file size.
- Shape
- An array of objects keyed by the header row — the shape APIs and JavaScript consumers expect.
- Encoding
- UTF-8 out; input is decoded through UTF-8, UTF-16 and cp1252 in turn so real-world exports do not fail.
- Delimiter
- Comma, semicolon, tab and pipe are all handled.
What it cannot do
Every conversion loses something. These are the limits of this one, stated up front rather than discovered in the output.
- Everything is a string. CSV does not record types, and guessing turns a leading-zero product code into a number.
- Nested structure cannot be inferred from a flat file; dotted column names stay flat keys.
- The first row must be the header.
- Ragged rows are padded rather than rejected.
Frequently Asked Questions
Are numbers converted to JSON numbers?
No — every value stays a string. CSV carries no type information, and inferring it silently corrupts data: a product code with a leading zero becomes a number and loses the zero. Cast explicitly in your own code instead.
How large a file can it handle?
Large ones. The conversion streams in batches rather than materialising the whole file, so memory stays flat as the file grows. The limit is the upload cap, not RAM.
What JSON shape do I get?
An array of objects, one per row, keyed by the header row. That is what almost every API and JavaScript consumer expects.
Can I go back the other way?
Yes. JSON to CSV flattens an array of objects into a table, and it is the same streaming machinery in reverse.