- "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!"
- —Filius Flitwick's description of the charm[src]
Becoming Secret Keeper
When the charm is initially cast, one can choose more than one person to be Secret Keeper, though it is unknown if there is a limit as to how many people can carry the same secret in this way. Once the Secret Keeper dies, all the people who have learnt the secret from them will become the new Secret Keepers. If the Keeper has chosen not to reveal the secret to anyone (so that they are the only Keepers) then the secret rests with them forever.
It is unknown what criteria must be met before someone can qualify as a Secret Keeper. However, it appears that, to be eligible, one must be capable of divulging the secret if they wish to, as this would explain why wizards do not simply bestow the secret onto creatures who cannot speak a human language, or creatures such as house-elves, who can simply be ordered by their masters to not divulge the secret (as such an order would override their free will). It is also possible that the spell must be cast by the Secret Keeper him/herself, so only a wizard can be it.
Revealing the secret
- "Lily and James only made you Secret-Keeper because I suggested it... I thought it was the perfect plan... Voldemort would be sure to come after me, would never dream they'd use a weak, talentless thing like you... It must have been the finest moment of your miserable life, telling Voldemort you could hand him the Potters."
- —Petter Pettigrew betrayed the Potter's secret[src]
The people to whom the Secret Keeper has already divulged the information (secondary Keepers) would not be able to pass it along even if they wanted to and the information in question cannot be learned even by stumbling across it, even if one were staring the secret in the face. For example, if someone were to hide a location in this way, even if a person were to stumble into the specific area they would not be able to recognise it for what it was (i.e. as the area they were looking for) and they would not therefore learn the location accidentally.
The method for the primary Keeper to voluntarily tell another person the secret can be verbal or written. It is also possible that primary Keepers can reveal information to another by showing it to them. This theory is postulated because whilst 12 Grimmauld Place was under this charm and being used as a base of operations for Harry, Hermione and Ron only after Dumbledore's death, the Death Eaters evidently became aware of 12 Grimmauld Place's approximate location knowing that Harry Potter had inherited the property from Sirius Black.
Despite watching the gap between numbers 11 and 13 when on the lookout for Harry, the house remained invisible to them until Yaxley grabbed onto Hermione Granger's arm while she, Harry, and Ron Weasley Disapparated away from the Ministry of Magic to 12 Grimmauld Place, where they had been hiding. It is explained that because Hermione (along with everyone else who knew the house's location) had been rendered Secret-Keeper by Dumbledore's death, she inadvertently took Yaxley past the protections of the Fidelius Charm. The trio subsequently abandoned the house as a hideout.
Once the secondary Keeper has received the information in either of these ways the information will still appear hidden to them until they start thinking about it, at which point the secret will reveal itself to them alone. For example, Alastor Moody gave Harry Potter a parchment with Albus Dumbledore instructing where the Order of the Phoenix's headquarters is. He then merely has to think about the said location whilst in the correct area and it would appear out of thin air, allowing him entry.
|Albus Dumbledore (possibly)||1979-31 October, 1981||The Fidelius Charm was used to protect James, Lily, and Harry Potter from Lord Voldemort at their home in Godric's Hollow, the location of which was the secret entrusted. They designated their Secret-Keeper as Sirius Black, but then switched to Peter Pettigrew at the last minute before the spell was cast as they thought it would be less obvious; they had refused Albus Dumbledore's offer to be secret keeper due to them preferring their friends, which proved a deadly mistake — Pettigrew betrayed them to Lord Voldemort, who found and murdered the Potters, with only Harry Potter surviving the attack.|
|1995-1996||The Fidelius Charm was once more employed to cloak the base of the Order of the Phoenix at 12 Grimmauld Place. However, in 1997 when Albus Dumbledore (primary Keeper) was killed, the members of the Order of the Phoenix automatically became Secret-Keepers for the HQ. This included Severus Snape, whose allegiance was doubtful at the time. As such, the Order was forced to abandon their headquarters.|
|Unknown||1997-1998||Bill Weasley used this charm on his households in 1998.|
|Arthur used this charm on his households in 1998.|
"Fidelis" is Latin, meaning trustworthy and faithful. "Fidelius" is the neuter comparative form of this word, meaning more trustworthy and more faithful. "Fidelius" can also translate to authors.
Behind the scenes
- It's very likely that all people who already knew the information before the spell is cast automatically become secondary keepers upon casting, even if they are unaware of the fact. That renders them uncapable of sharing the information, but they still remember it themselves. Otherwise the Fidelius Charm could be used as a powerful brainwashing spell that affects all living humans, up to making well-known facts forgotten and impossible to rediscover. This explains why Dumbledore immediately knew where Hagrid should look for Harry after his parents' deaths, even though Dumbledore had not been told the location of the Potters' house by its Secret Keeper.
- Harry Potter and the Deathly Hallows contained a few notable discrepancies regarding the Fidelius Charm. For example, it is not known whether or not Yaxley had learned the location of 12 Grimmauld Place by "piggybacking" on Hermione, or even if he had comprehended where he had been taken by Hermione; he may simply have stumbled out of the hideout unaware of his true location between exiting and entering it.
- When the Weasley family was forced into hiding, Bill told them that Arthur was Secret-Keeper and also told them that they were staying at Aunt Muriel's. Since Arthur was Secret-Keeper, it would logically follow that Bill should not have been able to tell the trio about the Weasleys' whereabouts. Also, when Harry, Ron, and Hermione were captured and taken to Malfoy Manor, Ron told Dobby where to take the hostages when the house-elf came to rescue them. There are several theories to explain these incidences: whilst it is possible that Bill and Arthur were both Secret-Keepers for Muriel's, and that Ron had been made into an additional Secret-Keeper for Shell Cottage, this was never specified. It is more likely that the Fidelius charms were cast after the trio arrived at the cottage, since Bill and Arthur would not have known that they were in immediate danger until after the first group of escaped prisoners arrived at Shell Cottage. Or perhaps it is due to the fact that elf magic is beyond that of wizard magic (i.e. being able to apparate in/out of Hogwarts, being able to apparate in/out of Malfoy Manor). However if house elves can bring people into protected places without permission, any one can ask a house elf to break into any places if he owns that house elf.
- Also, the Fidelius Charm appears to keep the secret location hidden even upon a Taboo Jinx being triggered within it, such as the one placed on Lord Voldemort's name after the Fall of the Ministry of Magic. Several times, unaware of the Taboo, Harry and Hermione say Voldemort's name on 12 Grimmauld Place, yet when the Death Eaters appear in the square outside, they are still not able to see the house. This directly contrasts the result of Harry saying the name while in the tent, which was followed immediately by the enchantments and charms placed there disappearing and a team of Snatchers Apparating outside.
- It is also worth noting that, when Dumbledore died, Snape would have become a primary Secret-Keeper. Therefore, he should have theoretically been able to tell the Death Eaters the location of Grimmauld Place. However, it was not until Hermione accidentally leading Corban Yaxley to the place did the Death Eaters (possibly) discover it. Snape either must've chosen not to reveal the location because of his secret loyalty to the Order, or may have been unable to reveal the location because of the Tongue-Tying Curse cast by Alastor Moody. Neither of these theories are ideal, though, since Voldemort would likely have tortured, or even killed, Snape had he declined to reveal the location, and if a tongue-tying curse was used to keep Snape from talking, that would kill the theory mentioned above that, to be secret-keeper, one must be capable of revealing the secret if they choose to (which, in turn, would beg the question as to why only humans, and not house elves or common animals, are never chosen as secret-keepers).
- Rowling once stated that, should the Secret Keeper die, anyone who knew the secret would be permanently unable to pass it on. Obviously, this is no longer the case.
- It should be noted that even the inhabitants of the secret location can become a Secret Keeper, so one must wonder why James or Lily didn't become their own Secret Keeper, instead of having their friends become one which would have effectively made them a prime target for Voldemort. But this can be explained by what Flitwick says in the third book: "not even if he had his nose pressed against their sitting room window!". Suggesting that in the Potter's case not the location but James and Lily themselves are the secret. Meaning that when one of them was the secret keeper nobody would be able to see or hear them and they wouldn't be able to disclose their secret to anyone else.
- The Potter's house was the secret. Lily mentioned in her letter that James had grown tired of being cooped up in the house. They needn't have stayed in the house if they themselves had been the secret. It's also said the charm was cast on their house.
- Harry Potter and the Prisoner of Azkaban (First mentioned)
- Harry Potter and the Order of the Phoenix
- Harry Potter and the Order of the Phoenix (film)
- Harry Potter and the Deathly Hallows
- Harry Potter and the Deathly Hallows: Part 1
- Harry Potter and the Deathly Hallows: Part 2