Convert JSONL to CSV in your browser

One JSON object per line, no surrounding array: that is JSON Lines, also called NDJSON or newline-delimited JSON. It is what log shippers, Elasticsearch bulk exports, OpenAI fine-tuning and batch files, LLM eval sets like GSM8K, and most data pipelines write, because a file can be appended to and split without re-parsing.

Spreadsheets don't read it. This page opens .jsonl, .ndjson and .ldjson files with DuckDB inside your browser tab and turns them into a table you can filter and export.

Lines rarely have identical keys. The columns are the union of the keys found while reading (the whole file up to 50 MB, a sample above that), and a key that is missing on a line becomes an empty cell. Nested objects flatten into dot-path columns like request.headers.host, up to 4 levels and 200 columns.

Arrays stay as JSON text inside the cell, so a log line with a tags array keeps its tags in one column. Types are detected per column: numbers stay numbers, true stays a boolean, and a column that mixes shapes is kept as text.

Export writes the current view. Filter with level:error or status:>=500, add -level:debug to drop noise, hide the columns you don't want, and the CSV follows. Plain filters have no row cap; SQL results stop at 1,000,000 rows.

Aggregates are a query away: SELECT path, count(*) AS hits FROM data GROUP BY 1 ORDER BY 2 DESC and then Export, as CSV or as a Markdown table for a ticket.

UTF-8, comma separated, one header row, values quoted when they contain commas, quotes or line breaks, nulls as empty cells. Text that starts with =, +, - or @ gets a leading apostrophe, so a spreadsheet won't treat a logged payload as a formula.

The same Export menu writes Parquet with zstd compression, a JSON array, JSONL again (after filtering) and a Markdown table of the first 1,000 rows.

The limit is 1.5 GB per file, the memory of one tab. Past that, DuckDB on your machine does the same thing: duckdb -c "COPY (SELECT * FROM read_json('logs.jsonl')) TO 'logs.csv' (HEADER)".

Going from CSV to JSONL is the same Export menu on the CSV to JSON page. To hand the table to someone, press Share or run curl -T logs.jsonl https://rows.page: files up to 100 MB, link deleted after 7 days unless you keep it.