Add UUID Column to CSV Files Online

What is the difference between UUIDv4 and UUIDv7 when adding to a CSV 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 CSV 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 CSV 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.