As per wiki, Bcrypt is a password hashing function designed by Niels Provos and David Mazières, based on the Blowfish cipher. Bcrypt uses adaptive hash algorithm to store password which is a one-way hash of the password. BCrypt internally generates a random salt while encoding passwords and store that salt along with the encrypted password. Hence it is obvious to get different encoded results for the same string. But one common thing is that everytime it generates a String of length 60.
Following is an online tool to generate and compare Bcrypt password.
Any plain-text input or output that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen.
For bcrypt encryption, first enter the plain text that you want to encrypt. It can be any plain text. Now select the salt round. Salt round represents the cost factor and cost factor is directly propotional to amount of time needed to calculate a single BCrypt hash.Now you can submit the form to generate the bcrypt hash online for the plain text that you have entered.
Similarly, to match a hashed password you require to provide the hashed password and the plain text to match with. Doing so the tool will compare the both inputs and give result whether the hashed password and plain text matched or not as true and false.
There is a difference between Hashed which start with "2y" and others which start with "2a". they are different variants of BCrypt from improvements over the years, some old implementations will not work with the newer ones as such I had to use this older implementation of 2a and 4 rounds to replace a hash in a db for some older software so I could get in vs other sites which use 2y.
Ideally, the older implementation should be replaced with a newer one and use more rounds over time. This can be facilitated by re-hashing the users plain text password on next login with the new way, you can do a string check on the first 6 characters (or better yet split by $ and look at first two indices).