While this tool uses the proper BIP39 library, it runs in a browser environment. For production wallets, generate mnemonics offline on an air-gapped computer using trusted hardware or software.
BIP39 is a Bitcoin Improvement Proposal that defines how to generate mnemonic phrases for deterministic wallets.
These phrases consist of 12-24 words from a standardized list of 2048 words, making it easier to backup and restore wallets.
The mnemonic phrase can generate all private keys for a hierarchical deterministic (HD) wallet.