According to Filius Flitwick the Fidelius charm is:

"An immensely complex spell involving the magical concealment of a secret inside a single, living soul. The information is hidden inside the chosen person, or Secret Keeper, and is henceforth impossible to find — unless, of course, the Secret Keeper chooses to divulge it. As long as the Secret Keeper refused to speak, You-Know-Who could search the village where Lily and James were staying for years and never find them, not even if he had his nose pressed against their sitting room window!"

So this charm is all about trusting someone, the secret keeper, to hide an information within his or her very soul. In this case the location of the Potters.

Does that mean the Fidelius charm is limited to hidding places? From your understanding of canon could it be possible to hide another type of information such as the incantation and wand movments of the unforgivables, the recipe of a dangerous potion or even the very existence of an indivual?

Thanks for your input.

2 Answers 2

  1. The wording on Pottermore confirms Flitwick's exact wording - the charm is about concealing information, not specifically location of a place.

    "The Fidelius Charm is extremely ancient and still used to this day. It involves the concealment of information inside a living person. The chosen person, or Secret Keeper, is the only person who is thenceforth capable of revealing the protected information to others, however many previously knew it. If the Secret Keeper shares the hidden information, the person to whom he or she has confided it will be bound by the Fidelius Charm and find it impossible to pass the information on.

  2. Having said that, there's only 3 known cases of Fidelius charms in the entire universe, and all 3 were locations (Potters' house; Order Headquarters; and Weasley's various places in DH). However, it would be a logical fallacy (Hasty generalization) to assume that this means no other information can be hidden using Fidelius.

  3. Having said THAT, hiding a recipe for a potion is less effective, as someone can discover the potion recipe independently.

    It's not known from canon if existence of individual can be hidden; I am at a loss as to find a case in canon where it would be of great benefit to hide the existence of a person and feasible to do so (e.g. hiding Harry's existence would be impossible as Voldemort knew of the pregnancy already). However, if someone could find an example, they would have had a good answer of "no".

Please note that the way Fidelius is treated is somewhat weird and I daresay inconsistent in Potterverse:

  • If you make a house (whose location was well known) covered by Fidelius, the house now becomes un-plottable and invisible.

  • Yet, if you apply similar logic to a person (which is never stated to be outside the limits) it should make the person "un-plottable" and invisible as well. Which if it would be true oughtta have been done on Harry Potter ASAP.

  • So the FC would be useful only for a previously unknown information right? Too bad, I was thinking of the endless possibilities, no more Unforgivable curses, no more dark arts...as long as the secret keeper stays silent and alive. Imagine secret keeper+Elixir of life/Horcruxes, there could be entire famillies dedicated to keeping these secrets or famillies wanting to keep their own brand of magic for themselves, reaping the benefits from the defacto monopoly, and others willing to pay anything to learn some secrets. Gringotts would also provide "secret-breaking services"...Fanfic material!
    – user24308
    Apr 14, 2014 at 1:06
  • I count that as four cases: Potter's house, the Order HQ, the Burrow, and Shell Cottage.
    – b_jonas
    Apr 14, 2014 at 5:23

It's never really alluded to. But, the Unspeakables in the Department of Mysteries might utilize the Fidelius Charm to hide their research.

  • Is this pure speculation or do you have any evidence that led you to this idea you could edit in?
    – TheLethalCarrot
    Feb 28, 2019 at 20:55
  • It's really speculation. If that violates some rule I'll delete it. It's no more concrete than the ideas posted with the question. I got the idea from the Unspeakables themselves. I wondered what made them "unspeakable". So I made a play on the name. The Fidelius Charm itself is inconsistent in it's use and capabilities throughout the series. It's possible that Unspeakable's could be Secret Keeper's for the Ministry. Where and how else would the Ministry keep its secrets?
    – Wayne
    Mar 9, 2019 at 5:50

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