Last updated 06-APR-11.
While most unlock codes are sourced from the manufacturers themselves, some people have taken a more hands-on approach to obtaining them. In certain cases, the algorithms that link IMEIs to unlock codes have been reverse engineered and leaked to the public. As hackerish as this sounds, this means that there's a large collection of free unlock codes online (admittedly for older handsets and only for certain brands). The method used to unlock is the same: you type in a few codes and voila!
What phones are covered by these free unlock codes?
Many old Nokias (DCT3 and DCT4), LGs, Panasonic and Siemens phones can be unlocked using this method. However, the majority of phones cannot, so count yourself lucky if you manage to get it done without paying any money! Trycktill and Unlock Nokiafree, are two popular free sites. Definitely worth a try.
If you haven't managed to get your phone unlocked for free, there are plenty of online codes that you can pay for to get the job done.
For other ways to unlock your phone check out our main page on this topic