Bip39 Trust Wallet Or for incredibly substantial security, you could potentially "roll your own" seed phrase with dice or maybe a calculator as offline strategies. You could see the complete resource code in standalone, offline html file. Alternatively you can Look at the individual css and js information in the https://top100bookmark.com/story18901813/bip39-compatible-non-custodial-wallet-detailed-notes-on-bip39-phrase