Free tool — nothing is uploaded
CSV / TSV to JSON
Paste your data or drop a file. The object array appears as you type, and the conversion runs entirely on your device — your data never leaves the browser.
Input
Drop a file anywhere in this pane · utf-8
Result
Your JSON appears here as you type.
What this converter does with your CSV
The first row is treated as the header unless you say otherwise, and the delimiter is detected from tabular consistency rather than from how often a character appears. Numbers only become JSON numbers when doing so cannot lose information — a leading zero or a value past the safe integer range stays a string, because a silently mangled zip code is worse than a quoted number. Rows whose field count disagrees with the header are reported with their line number instead of being quietly padded.
Why is 00721 still a string in the JSON?
Because turning it into the number 721 would destroy it. The same rule protects phone numbers, order IDs and anything wider than a double-precision integer. Use the Parse numbers switch to compare the two behaviours.
Is my file uploaded anywhere?
No. The conversion runs in a Web Worker on your machine and no request carries your input. You can confirm this in the browser network panel while converting.
What happens to rows that do not match the header?
They are reported in the Diagnostics panel with their line number, and you choose whether to pad them, drop them or fail outright. Nothing is discarded without telling you.
Converted in a Web Worker on your own machine. Nothing is uploaded, and no account or server is involved.