Is converting NDJSON to XLSX free?

Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.

Will my NDJSON data keep its types in XLSX?

Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real XLSX types rather than everything becoming text. The mapping table above shows exactly what you get.

Do you store my file?

No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.

Convert NDJSON to XLSX

Upload a .json or .ndjson file and get back a XLSX file. Types are preserved rather than flattened to text. Free, no registration, up to 10MB.

1Upload your file

Click to upload or drag and drop

CSV, Excel, SQLite, SQL, DBF (max 10 MB)

2Choose target format

How your data is typed in XLSX

Generated from the converter's own XLSX type mapping — this is what it actually emits, not an example.

Your data	XLSX type
Whole number	number
Decimal (money)	number
Floating point	number
True / false	boolean
Date	date
Date and time	date
Short text	text
Long text	text
Binary data	hex text

Working from an .ndjson file

Newline-delimited JSON is one complete object per line with no enclosing array, which is exactly what makes it appendable: a log or an export can keep growing without anything having to rewrite the end of the file.

→Each line is parsed on its own and blank lines are ignored, but a single malformed or truncated line fails the whole file - the usual outcome of copying a log that was still being written.
→Lines need not share their keys. The columns are what the records collectively use, and a record that omits one gets NULL in that column.
→A file that is one line long and wraps its array, {"rows": [...]}, is unwrapped into those rows rather than read as a single record.

Sheet names and cell types

The workbook is generated rather than exported out of Excel, so every choice in it is one the converter made. The two that show up the moment you open the file are what the sheet is called and what type each cell turned out to be.

→The sheet takes the table's name cut to 31 characters, which is Excel's own limit for a tab, while the workbook file keeps the name in full - so a long table name is complete in the file name and shortened on the tab inside it.
→Dates and timestamps become genuine date cells, formatted yyyy-mm-dd and yyyy-mm-dd h:mm:ss, rather than strings that merely look like dates. Sorting and date arithmetic work on them with no conversion step first.
→A text column of digits stays text: a value like 01234 is written into a string cell, and Excel shows it as it was stored instead of dropping the zeros the way it does when the same data is opened from a CSV.

Reading NDJSON

→JSON types are trusted: 1 and "1" stay different things.
→Numbers with a decimal point are read as exact decimals rather than floats.
→Both an array of objects and newline-delimited JSON work, and a wrapped array like {"data": [...]} is unwrapped automatically.
→Nested objects are kept as JSON rather than flattened into invented column names.

Writing XLSX

→One file per table. Booleans stay booleans and numbers stay numbers.
→Excel has no fixed-point type, so decimals become numbers — use a database target if exactness matters.

What you get

A ZIP containing <table>.xlsx. If anything about your data needed a judgement call, a _warnings.txt explains it.

Questions

Is converting NDJSON to XLSX free?: Yes. Files up to 10MB convert free with no account. There is a limit of five conversions per day per IP address.
Will my NDJSON data keep its types in XLSX?: Yes — that is the point. Whole numbers, decimals, dates and booleans are mapped to real XLSX types rather than everything becoming text. The mapping table above shows exactly what you get.
Do you store my file?: No. The file is written to a temporary directory, converted, and the directory is deleted as soon as your download has been sent.