Convert CSV to JSON (and back) — without uploading.

CSV is flat by nature, so if your CSV has a column like address with a JSON string in it, converting produces a JSON object with that cell as a string value. Example: {"address":"123 Main St"}. If you need deep nesting from CSV, parse the CSV into JSON and then post-process the specific columns in a script.

Array of objects: one big [{...}, {...}, ...] — standard for REST APIs. NDJSON (JSON Lines): one JSON object per line, no surrounding array — standard for log pipelines, BigQuery imports, and streaming. NDJSON scales better for huge files because readers can process one line at a time.

Yes — nested objects and arrays are serialized as JSON strings in the CSV output. Example: {"tags":["a","b"]} becomes a cell with value ["a","b"]. This is different from most tools that either drop these fields or produce broken "[object Object]" cells.

Sparse means some objects have keys that others don't. The tool unions all keys across every object and produces one column per key. Missing values become blank cells. Your output CSV has every field — nothing is silently dropped.

No. Numbers are written as bare numbers: 42, not "42". Strings are quoted only when they contain commas, quotes, or newlines.

null becomes an empty cell in CSV. true and false become TRUE and FALSE strings. On JSON output the types are preserved correctly.

Use the JSON → CSV tab — there's a textarea to paste your JSON. Up to a few MB works fine. For larger JSON, save to a file and use the CSV → JSON flow in reverse (drop the file and change the download to CSV).

Yes. If you paste invalid JSON, you'll get a clear error pointing to roughly where the parse failed. Common causes: trailing commas (not valid JSON), single quotes instead of double, or missing outer brackets.

Your browser's memory. Very large JSON (500MB+) may be slow to pretty-print — use the "Minified" output option for faster processing at the cost of readability.

Yes — "💾 Save settings" stores your JSON output format (array vs NDJSON) and indent level. Reload the tool and those defaults are applied automatically.

JSON array gives you [{"id":1,"name":"Alice"},{"id":2,"name":"Bob"}] — a single document. Most APIs, frontend apps, and tools like jq expect this. NDJSON (newline-delimited JSON) puts one JSON object per line — {"id":1,"name":"Alice"} then {"id":2,"name":"Bob"}. NDJSON is the standard for streaming pipelines, BigQuery imports, ElasticSearch bulk API, and large log-style files because each line can be processed independently.

Click the JSON → CSV / XLSX tab, paste your JSON (array of objects) or drop a .json file. The tool flattens the first level of keys into columns — so {"name":"Alice","email":"[email protected]"} becomes name,email columns. Pick CSV, TSV, or XLSX as the output format. Nested objects get serialized as JSON strings; for deep flattening you'll need to pre-process.