The Age Line

• Incantation: Unknown. The line is created through a powerful Charm.
• Wand Movement: Unknown.
• Light: A thin, golden line.
• Effect: Creates a magical barrier that prevents anyone below a specified age from crossing it. Those who are too young and attempt to do so are repelled, often with a humorous but harmless side-effect, such as being aged up rapidly and sprouting a long white beard.
• Type: Charm.

The only known instance of an Age Line was during the 1994-1995 school year at Hogwarts School of Witchcraft and Wizardry. Albus Dumbledore cast the charm to form a perimeter around the Goblet of Fire after it was placed in the Great Hall. The line's explicit purpose was to enforce a new rule for the Triwizard Tournament, which stated that only students aged seventeen or older were eligible to enter their names. Dumbledore referred to the Age Line as a “measure of safety” designed to protect younger students from the notoriously dangerous tasks of the Tournament. The enchantment manifested as a simple, thin, golden line on the stone floor, encircling the stool upon which the Goblet of Fire rested. Several underage students attempted to circumvent the line to enter the Tournament:

• Fred Weasley and George Weasley each took a dose of an Ageing Potion, believing it would fool the line into thinking they were seventeen. While they managed to cross the golden line and place their names into the Goblet, they were immediately and forcefully ejected, landing several feet away and instantly growing identical long, white beards. Hermione Granger had previously warned them that such a simple potion was unlikely to outsmart a powerful enchantment cast by Dumbledore.
• A student from Beauxbatons Academy of Magic and another from Durmstrang Institute also made unsuccessful attempts to cross the line.

The Age Line proved effective in preventing any underage student from entering their name legitimately. However, it did not prevent Barty Crouch Jr., while disguised as Alastor Moody, from putting Harry Potter's name into the Goblet of Fire by using a powerful Confundus Charm on the Goblet itself. The line was presumably removed after the three Triwizard Champions (and Harry Potter) were chosen.

Casting an Age Line appears to be a piece of highly advanced and powerful magic, as demonstrated by its resilience to countermeasures. As it was cast by Albus Dumbledore, it possessed immense strength and sophistication. Hermione Granger's correct theory that a simple Ageing Potion would fail against it implies that the charm is complex enough to detect magical trickery and not just the physical age of the person crossing. There are no known counter-spells or methods to disable an Age Line, other than the original caster presumably removing the enchantment.

The name Age Line is purely descriptive. Age refers to the criterion it uses to filter individuals, and Line refers to its physical manifestation as a line drawn upon a surface.

• In the film adaptation of Harry Potter and the Goblet of Fire, the Age Line is visually different from its description in the novel. Instead of a thin golden line on the floor, it is depicted as a large, translucent, shimmering blue dome of magical energy that encircles the Goblet of Fire. The effect of being rejected is also more spectacular; Fred and George Weasley are launched high into the air across the Great Hall before their beards appear. (film)