The Unlocking Spell (Alohomora) is one of the spells found in Harry Potter and the Philosopher's Stone.
The Unlocking Spell is one of the spells in the spellbook The Standard Book of Spells, Grade 1. It can not be used in Dueling. It is, however, used in one of the moments in Harry Potter and the Philosopher's Stone, "The Forbidden Corridor".
The Unlocking Spell unlocks (magically) locked doors. It may not always work, as some doors may be warded against its effects.
The Unlocking Spell is used in Harry Potter and the Philosopher's Stone, Chapter 9, Moment 3 to unlock the door to the Forbidden Corridor, and must be cast successfully to unlock Spells in the Navigation Bar and progress through the book.
Its full incantation is "Alohomora", but the letters used in its casting are: A, O, H, M, A.
As a non-duelling spell, the Unlocking Spell has no potency and is either cast successfully or not at all. It can be re-attempted if it fails.
Pottermore Playstation Home
On Pottermore PlayStation Home, the Unlocking spell is a spell available in the Book Herding game. When a player moves over the spell icon, the cages of the other player(s) will unlock, releasing all the books that were already captured inside, giving the caster an advantage.