Bip39 Mnemonic Phrase Tool Regardless that it utilizes BIP32 system you could still import BIP39 seeds into Electrum wallet. Also other than BIp32 There's BIP44 Variation which some wallet use to the technology of seeds. It is possible to see the entire source code in standalone, offline html file. Alternatively https://bookmarkingquest.com/story18504310/how-to-generate-seed-phrase-seed-phrase-generator-an-overview