JSON to CSV Converter

CSV (comma-separated values) remains the most universally supported tabular data format: every spreadsheet application, database import tool, and data pipeline can read it, whereas JSON — despite being the web's default data interchange format — is not something most non-technical tools open directly. Converting a JSON array of objects into CSV is one of the most frequent "glue" tasks in day-to-day development and data work: exporting an API response for a colleague to open in Excel, turning a database query result into a report, or preparing data for a bulk-import tool that only accepts CSV. The conversion works on a JSON array where each element is an object — for example, a list of user records or product rows. The header row is built from the union of every key that appears across all objects in the array, not just the keys in the first object, so if some records have an extra field that others lack, that field still gets its own column and simply appears blank for rows that don't have it. Objects nested one level deep are flattened using dot notation — a field like `address: { city: "London", postcode: "E1 6AN" }` becomes two separate columns, `address.city` and `address.postcode` — which keeps the output genuinely tabular rather than dumping a stringified object into a single cell. Arrays found as a value (rather than as the top-level input) are serialised to a compact JSON string within their cell, since a CSV cell cannot itself hold a nested list. Quoting follows the standard CSV convention (as used by RFC 4180 and virtually every CSV parser in practice): any field containing a comma, a double quote, or a line break is wrapped in double quotes, and any double quote inside that field is doubled (`"` becomes `""`) so it round-trips correctly when read back. Fields that don't need quoting are left bare, keeping the output readable. Getting this right matters — a naive CSV export that just joins values with commas will silently corrupt any value that happens to contain a comma (an address, a product description, a note field), producing a file with the wrong number of columns on some rows and no error to warn you. If the pasted input isn't valid JSON, isn't an array, or is an array that doesn't contain objects (for example, an array of plain numbers or strings), the tool shows a clear inline error explaining what it expected instead of silently producing an empty or nonsensical CSV.