Quote from: jerry0 on March 07, 2021, 08:22:16 PM

Okay just to confirm, so if someone were to try to brute force and say the seed they wrote down is incorrect... it would show an error right such as this seed is not correct?

BIP39 seed phrases have a checksum built in to them. If you have the incorrect words, then with a 12 word seed phrase there is a 1 in 16 chance on average of having a correct checksum by pure luck. With a 24 word seed phrase, there is a 1 in 256 chance on average of having the correct checksum by pure luck. Most wallets would not let you proceed with an invalid checksum, but some like Electrum will simply tell you the checksum is invalid but still allow you to generate a wallet using that seed phrase. Note that a seed phrase with an incorrect checksum will generate a different wallet when compared to the same seed phrase with the correct checksum (or the same seed phrase with a different incorrect checksum).

Quote from: jerry0 on March 07, 2021, 08:22:16 PM

Still... how is it possible that a seed can't be brute forced if there are so many addresses out there and so many wallets?

Because a 12 word seed phrase encodes 128 bits of entropy. This is the same security as any given bitcoin address. The reason people can't just randomly guess private keys is the same reason people can't just randomly guess seed phrases - the human race would be extinct before you even searched a tiny fraction of a millionth of a percent of all the possibilities.