Hash & Anonymise Columns in NDJSON Files Online

What is the difference between MD5, SHA-256, and the fast hash option in a NDJSON file?

MD5 produces a 32-character hex string. SHA-256 produces a 64-character hex string and is cryptographically stronger. The fast hash option is a 64-bit non-cryptographic hash returned as a string — useful for quick deduplication or partitioning but not for security-sensitive anonymisation.

Does hashing a column in a NDJSON file actually anonymise the data?

Hashing replaces the original value with a fixed-length digest that cannot be reversed. However, for low-entropy values like common names or small integer IDs, an attacker with a list of possible values can hash each one and match the result — this is called a rainbow-table attack. For strong anonymisation of predictable values, consider salting the input first using the Calculate Column tool before hashing.

Will two rows with the same original value produce the same hash in a NDJSON file?

Yes. Hashing is deterministic — identical inputs always produce identical outputs. This is useful for joining anonymised datasets: two files hashed with the same algorithm on the same column can still be joined by the hash value without exposing the original data.

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.