Add UUID Column to Parquet Files Online
Add a UUID column to Parquet files directly in your browser. Generate random UUIDv4 or time-ordered UUIDv7 identifiers for every row. Choose the column name and position — no upload required.
About this tool
Add a universally unique identifier column to every row in a Parquet file. Choose between UUIDv4 (fully random, widely supported) and UUIDv7 (time-ordered, ideal for database primary keys because it sorts chronologically and avoids B-tree index fragmentation). Set the column name and whether it appears as the first or last column in the file. Each run generates fresh UUIDs — if you need stable, repeatable IDs tied to existing data, use the Hash Columns tool instead. Your data never leaves your device.
Frequently Asked Questions
What is the difference between UUIDv4 and UUIDv7 when adding to a Parquet file?
UUIDv4 is fully random — every UUID is independent and unordered. UUIDv7 encodes a timestamp in the first bits, making the UUIDs monotonically increasing over time. UUIDv7 is preferable as a database primary key because it sorts in insertion order, which avoids index fragmentation.
Are the UUIDs added to a Parquet file truly unique?
Each UUID is generated independently using uuid() or uuidv7(). The probability of a collision between two random UUIDv4 values is astronomically small (roughly 1 in 5 × 10^36). For UUIDv7, the timestamp prefix further reduces collision risk within the same millisecond.
Can I add a UUID column to a Parquet file and still join it to another file?
No — because each run generates new random UUIDs, two runs on the same file will produce different UUIDs. If you need stable, repeatable IDs for joining, use a hash of an existing unique column instead (see the Hash Columns tool).
Is my data private?
Yes — completely. Your file is never uploaded to any server. Everything runs locally in your browser using WebAssembly — processing happens entirely inside your tab. Once you close the tab, nothing is retained.
What is the maximum file size?
The free limit is 50 MB. For larger files, performance depends on your device's available memory — most modern machines handle 500 MB to 1 GB comfortably.
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