zxcvbn has problems but your example is backwards. "aaaaa" gets (as it should) low entropy because it is a single repeated character. It is more likely to be us

zxcvbn has problems but your example is backwards. "aaaaa" gets (as it should) low entropy because it is a single repeated character. It is more likely to be used than "rqntd". The major limitations are that it is worthless for estimating entropy of passphrase (which is what it's being used for here) and words not in its dictionary (non english).