How to migrate user accounts without forcing password resets

Identity migration guides routinely tell users they must reset their passwords, but this is a design choice rather than a technical necessity. Standard password hashing algorithms like bcrypt and PBKDF2 are self-describing and portable, meaning any compliant system can verify a hash produced by another without ever knowing the plaintext password. A technique called lazy migration allows the old hash to be verified on first login and silently replaced with a new one, gradually rehashing the entire user table over normal login activity with no user-facing disruption. The main challenge varies by source: ASP.NET Identity hashes migrate cleanly by default, while Auth0 requires a support-assisted bulk export to obtain bcrypt hashes, since its Management API deliberately withholds them. Forcing password resets during migration increases support load, erodes user trust, and turns a silent infrastructure change into a visible disruption that can be avoided with the right tooling.