Password strength measurements

We fail to detect whether the measurements are 100% accurate since it is time-consuming to crack each password and then count the time. But we can judge whether the measure is reasonable. For example, a password manager would warn us the password is not safe enough if the passwords only consist of four digits. Therefore, password managers mentioned here who have the features of password strength measurements are trustworthy. And in this passage, we focus on whether password managers have this feature or not rather the effectiveness of this feature of each password manager. Future research may focus on it.