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Frequently asked questions
Everything you need to know about converting JSON to CSV — privacy, features, limits, and more.
- Does my data get uploaded to a server?
- No. All conversion happens entirely in your browser using JavaScript. Your JSON files are never sent to any server, stored in any database, or transmitted over the network. The tool uses the FileReader API for file reading and Blob/Object URL for download — everything stays in your browser tab.
- What data does the tool store?
- Only your browser's localStorage is used: your most recent JSON input (so you can resume after a refresh), your option preferences, and a local history list with metadata only (row count, column count, timestamp) — never the actual JSON content. You can clear all of this at any time.
- Does the tool work offline?
- Yes. Once the page has loaded, the converter runs entirely in-memory. No internet connection is needed for conversion, download, or clipboard copy.
- What types of JSON can I convert?
- Arrays of objects (most common), single objects (one-row CSV), nested objects (auto-flattened), objects with array values (expanded or stringified), and arrays with inconsistent keys across rows.
- How does nested JSON get converted?
- Nested objects are flattened using dot notation by default. {"user": {"name": "Alice"}} becomes column user.name. You can change the separator or enable Stringify nested to keep objects as JSON strings.
- What happens if rows have different keys?
- All unique keys across every row are merged into one column list. Missing values become empty cells (or your configured empty value). No data is lost.
- What delimiters are supported?
- Comma (standard CSV), semicolon (EU Excel), tab (TSV), and pipe. Choose in the Options tab.
- How do I open the CSV in Excel without encoding issues?
- The downloaded CSV includes a UTF-8 BOM at the start, which signals Excel to use UTF-8 encoding — ensuring special characters and non-Latin scripts display correctly.
- What is the maximum file size?
- There is no hard limit. The practical limit is your device's memory. Files up to 50 MB work well on modern devices. A warning is shown for files over 50 MB.
- Is there a keyboard shortcut?
- Yes. Press Ctrl+Enter (Cmd+Enter on Mac) to trigger conversion from anywhere on the page.
- Is the tool accessible?
- Yes. Built with semantic HTML, ARIA labels, keyboard navigation, visible focus indicators, and WCAG 2.1 AA-compliant colour contrast.
- Are boolean values preserved correctly?
- Yes. true becomes "true" and false becomes "false". Numbers are preserved as their exact string representation.