All password "strength" testing tools that work by analyzing a user-entered password example produce invalid results. They are for entertainment purposes only, and should never be relied on to make decisions related to cybersecurity. Bitwarden's tool is no exception. It is based on zxcvbn tool , which is somewhat better than other password testing tools, but can still produce wildly misleading results. In your case, you may have started with something like hge9e3&jg[s19, which the zxcvbn tool cannot match to its inventory of password patterns, so it conservatively estimates that 1013 guesses (a factor of 10× for each character) would be require to crack this password. It also assumes that an attacker would be limited to making 10,000 password guesses per second (which is unrealistic for your laptop password, but could be plausible for your Bitwarden master password). Thus, the cracking time is estimated to be 1 billion seconds, which is 31.7 years. If you now add a digit (e.g., 3) at the end of your password string (hge9e3&jg[s193), then the zxcvbn tool still cannot match the string to any of its password patterns, so it determines the number of required guesses to be 10× higher than before (1014 guesses). Thus, the estimated cracking time is also going to be ten times longer (317 years, a.k.a. "centuries"). If you now add one more digit (e.g., 4) at the end of the previous string (hge9e3&jg[s1934), then something interesting happens. In this case, the zxcvbn tool recognizes the pattern 1934 as a recent calendar year, a pattern commonly found in passwords. The zxcvbn algorithm therefore estimates that it would take at most 90 guesses to come up with the 1934 pattern by working backwards from 2024 (as opposed to its standard estimate of 10,000 guesses for a 4-character sequence with no recognized pattern). Therefore, the password is now parsed as a random 11-character string (hge9e3&jg[s, requiring 1011 guesses) followed by a 4-character year pattern (1934, requiring 90 guesses). The tool then applies a fudge factor of 2×, coming up with 1.8×1013 guesses for cracking this longer password. With an assumed guessing speed of 104 guesses/second, the cracking time ends up being 1.8 billion seconds, corresponding to 57 years. Do all of these assumptions seem arbitrary? They are. Can we trust the results? No. More on reddit.com

The other explanations here are true but maybe this will clarify why. Bad password checkers assume a cracking program will guess, in order: a, b, c, … aa, ab, ac, ad, … and so on forever. Good password strength checkers calculate entropy (~randomness) with the assumption of common reasonable wordlists and standard variations on those words, in addition to gibberish character strings. Password cracking tools don’t tend to guess every single random string of characters from shortest to longest, since many people are more likely to choose real words or variations of words. So, for example, “eggplan” is actually a stronger password than “eggplant” despite having fewer characters. They’re both awful, but any decent password cracking tool will guess a word a human is more likely to choose first (vs egg + plan, two unusual words to combine). “eggplan” will even take longer to crack than “eggpl@nt” because a→@ is such a common substitution for humans trying to strengthen their passwords that password cracking tools will likely try it first. Extending to longer sequences, 3-6 memorable unmodified words chosen randomly from very long lists will usually be both more memorable and harder to crack than 2-3 words with symbols inserted. Edit to add: the best way to get a sense of how this works in practice is here: https://lowe.github.io/tryzxcvbn/ More on reddit.com

Don’t use password strength testers… that’s what you missed. They just look for characteristics like length and characters used and aren’t really a good measure of how secure a password is. More on reddit.com

Don't ever type the real password you want to test into any online or offline testing. Instead you should construct a different password with similar structures and policies, and use it instead. Also, don't trust the tests because most of them used bruteforce to test, where real world attack uses complex methods like mask, permutation or Markov chain to break your passwords. Not to mention test site only tested to simulate a single machine for cracking, where real life attacker uses computer cluster or high power hardware like ASIC to break your password. More on reddit.com