Bip39 length https://www.tumblr.com/generalllamacolor/787594721599078400/can-you-depend-on-online-bip39-generators-a Even though it takes advantage of BIP32 approach you could however import BIP39 seeds into Electrum wallet. Also apart from BIp32 There's BIP44 version which some wallet use with the generation of seeds. It is really basic — if you don't concern yourself with copyright ... https://setbookmarks.com/story19910423/bip39-format-bip39-compatible-wallet-options-https-linktr-ee-bip39