CSV ⇄ JSON
Convert CSV to JSON and JSON to CSV. Supports header rows and tab-delimited data.
About this tool
CSV is a flat table for spreadsheets; JSON is a hierarchy for programs. This tool converts between them in your browser and never sends your data anywhere. CSV looks simple but is a surprisingly tricky format, so here are the points worth knowing before you convert.
CSV has no strict single standard
RFC 4180 exists as a de facto guideline, but delimiters, line endings, and character encoding vary by implementation. That is why "a CSV made somewhere will not open in another tool" happens so often. This tool lets you choose the delimiter (comma, tab, semicolon) and whether there is a header row.
When values contain commas, newlines, or quotes
Per RFC 4180, a value containing a comma or newline is wrapped in double quotes, and a double quote inside a value is escaped by doubling it as "". For example, the single value Yamada, Taro is written "Yamada, Taro". Ignore this quoting rule and columns shift and break, so take extra care when editing CSV by hand.
Everything in a CSV is a string
CSV itself has no types like number or date; the opening app decides how to interpret them. Open in Excel and you often hit accidents: leading zeros vanish (00123 becomes 123), large numbers turn into scientific notation, and date-like strings get converted to dates. Keep type-sensitive data on the JSON side, or watch the import settings when opening.
Nesting is a weak spot
Because CSV is a flat table, deeply nested JSON cannot be represented as-is. A single-level flat array of objects converts most cleanly. For complex structures, flatten just the fields you need before turning them into CSV.
How to use
- Choose "CSV → JSON" or "JSON → CSV".
- Paste your data to convert it instantly.
- Toggle "First row as header" and the delimiter (comma/tab/semicolon).
FAQ
Is my data sent to a server?
No. Conversion happens entirely in your browser; your input is never sent anywhere.
Can I change the delimiter?
Yes. Choose comma, tab, or semicolon — supporting TSV (tab-separated) and the semicolon style common in Europe.
Can I control the header row?
Yes. Toggle whether the first row is used as field names (keys). Without a header, columns are handled by position.
What if values contain commas or line breaks?
Data that follows standard CSV quoting rules (wrapped in double quotes) is parsed correctly. Broken quoting may cause an error.
Can nested JSON be turned into CSV?
CSV is a flat table, so deeply nested structures cannot be represented as-is. A flat array of objects converts best.
Are non-English text and encoding handled?
Data is treated as UTF-8, so non-English text is preserved. If you see garbled text opening in Excel, check the opening app’s encoding setting.