A comprehensive list of every shift code Gearbox Software ever released is available at the Orcz website, on the "Borderlands 2: Golden Key" page. The website lists shift codes in order of release date and includes all three versions of each shift code when possible.
Gearbox Software, the official developer of "Borderlands 2," approves all shift codes. Gearbox Software still releases shift codes for the game on a regular basis, usually through its Facebook and Twitter accounts. On March 23, 2015, the company released a new shift code for "Borderlands 2" that gives the user 25 Golden Keys when redeemed.