Bip39 Online Or for extremely high protection, you may "roll your own" seed phrase with dice or maybe a calculator as offline approaches. Make sure you remember to allow for Restoration from mnemonic phrases that have invalid checksums (or that you do not have the wordlist) The Vault12 Guard Resolution https://bookmarkproduct.com/story18623477/bip39-passphrase-the-fact-about-bip39-that-no-one-is-suggesting