If you are looking to regain access to a DVR system because the password was lost or the device was purchased second-hand, you are likely encountering one of the many generic "admin" defaults used by OEM (Original Equipment Manufacturer) devices. Many budget DVRs are rebranded units manufactured by a handful of companies (like Dahua or Hikvision) or use similar legacy firmware.

Do you see a or a serial number on your login screen?

I can help by finding the specific manual for your model if you share the manufacturer name. If you are locked out, you can:

If you are setting up a new device or have inherited one, you might need the default login. admin is the most common default username.