Schema drift shows up as empty columns
Events gain fields over time. Records written before a field existed get an empty cell for it, which is accurate rather than an error.
Convert JSONL to CSV
Log exports and event streams arrive as one JSON object per line. Getting them into a spreadsheet means reconciling records that do not all share the same fields — which this converter does by building the header from every key it sees.
- Runs in your browser
- No signup
- No upload
- Free
JSONLCSV
Runs on your deviceCSV
Options
Reading JSONL
Auto-detect reads the first rows and picks the separator that splits them consistently.
Turn off when the file starts straight into data. Columns are then named column_1, column_2, and so on.
Turns "42" into a number and "true" into a boolean. Values with leading zeros stay text so IDs and zip codes survive.
Which worksheet to convert. Filled in once the workbook is read.
Dotted path to the array of records, such as data.items. Leave empty to use the whole document.
Turns {"user":{"id":7}} into a user.id column. Arrays are kept as JSON text.
Pick the encoding the file was written in. Wrong encoding shows up as garbled accents.
Comma-separated words that should become null instead of text.
Writing CSV
Snappy is the default across Spark, DuckDB and pandas. Gzip is smaller but slower to read.
Turns a user.id column back into {"user":{"id":7}}.
Excel needs a byte order mark to open UTF-8 files with accents correctly.
Rows per row group. Larger groups compress better; smaller groups let readers skip more.
Converting…
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How this converter handles JSONL to CSV
- Reads each line as an independent JSON object, skipping blanks.
- Reports and skips malformed lines instead of aborting the conversion.
- Flattens nested objects into dotted columns.
- Builds the header from the union of all keys, so late-added fields are not lost.
Format differences
JSONL vs CSV
One JSON object per line, built for streaming and appending. Plain text rows that open anywhere, with no types and no schema.
| JSONL | CSV | |
|---|---|---|
| Type information | Strings, numbers, booleans, null | None — every value is text |
| Structure | One nested object per line | Flat rows and columns |
| Compression | None | None |
| Typical file size | Slightly under JSON | Baseline (100%) |
| Schema | Implicit, per line | Header row at best |
| Human-readable | Yes, one record at a time | Yes, in any text editor |
| Tool support | Log pipelines, LLM training sets, BigQuery | Universal |
Worth knowing
What to watch out for
The whole file is read before writing
The header has to be the union of every key, so every line is parsed before the first row is written. That is why memory, not file size, is the limit.
Nested log records get wide fast
Structured logs nested several levels deep can produce dozens of columns. Targeting a subset with a record path keeps it readable.
When you need this
Common reasons to convert JSONL to CSV
Analysing a day of logs in a spreadsheet
Filtering and pivoting in Excel is often the quickest route to an answer for a one-off question.
Sharing event data with non-engineers
CSV is the format everyone can open.
Importing into a CSV-only tool
Many analytics and CRM imports accept nothing else.
FAQ
JSONL to CSV questions
Is my file uploaded?
No. The conversion runs in your browser using WebAssembly and JavaScript. The file is read from your disk into a Web Worker, converted in memory, and handed back as a download. It is never sent to a server, so there is nothing for us to store, log or leak.
Is NDJSON the same as JSONL?
Yes. NDJSON, JSONL and JSON Lines all describe one JSON value per line. Both .jsonl and .ndjson extensions work.
What happens to lines that fail to parse?
They are skipped and counted, and the conversion reports the first failing line number. Truncated final lines in copied log files are the usual cause.
Why does my CSV have more columns than I expected?
Because the header is the union of every key across every line. One unusual record with extra fields adds columns that are empty elsewhere.
Will it open properly in Excel?
Turn on "Add BOM for Excel" if the data contains non-ASCII characters.
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