There's something of a tension in canon in this regard.

On the one hand, we have seen only very limited examples of "tracking magic" available to the Ministry. The Trace, which is limited to kids, and (possibly) the Taboo, which is limited to specific words. Other than that, the only example I can think of is Fantastic Beasts 1, the map of New York which shows where powerful magic is being cast.

We also know that you can't track apparition unless you physically grab the person.

So on that front, you'd think the Ministry would have limited ability to monitor magic around the country.

On the other hand, you have the fact that wizarding Britain seems to be a fairly lawful place, where wizarding law enforcement is (generally) quite effective. Azkaban is full of captured criminals. If the Ministry really was as limited as the above suggests, how would they ever catch any criminals at all?

Magic provides so many ways to get away with crimes, surely there must be some powerful tracking/monitoring magic that the Ministry has access to.

Similarly, the continued effectiveness of the Statute of Secrecy would, you'd think, require an ability to monitor magic cast in Muggle locations.

There are also some parts of canon which are quite plot holey unless you assume the Ministry has a high level of monitoring ability. For example, in DH when they are camping and complaining about having shitty food, the question is: why not go to a random Muggle town and buy (or steal) some nicer food? It would be so easy. The only real reason they wouldn't is if they couldn't, which suggests that if they had gone into a random Muggle town the Ministry would have known very quickly.

So:

1. What is your preferred balance of the Ministry's ability to track magic vs. individuals' ability to cast magic in private?

2. What are some interesting ways you can think of by which the Ministry could monitor magic?

One avenue I like for question 2 is animals - the Ministry had the ability to know about any magic cast in front of animals, that would give a significant but gameable monitoring ability to the Ministry.

 

I have thought about this quite a bit but I can't really come up with a good answer.

I really dislike the notion that you can have a map that shows wherever magic is being used and even the Taboo is kind of stupid because why not put a Taboo on "Avada Kedavra", "Imperius" and "Crucio"? Then the Graveyard in book 4 should have been full with Aurors immediately. If you can put up Wards to counter it why couldn't Hermione do that in Book 7? She was supposedly very skilled already even if she wasn't a fullly trained witch. But Voldemort only had Wormtail and Crouch Jr. to help him cast anything on the Graveyard unless he did so himself.

It's one of those plot holes that Rowling left open by not really being precise here. Pretty annoying.

A lot of fanfiction goes the easy road of tracking charms on the wands. Either in a way that wands know when someone is under 17 or that Olivander Wand's are spelled to notify the ministry for spells outside of Hogwarts for 7 years. But that goes against the evidence we see from the Ministry noticing Dobby's magic close to Harry but not knowing it wasn't Harry who cast it.

Let's look at the evidence of what the Ministry notices though:
-It doesn't notice when Hermione practes spells before first year.
-It does notice Dobby's magic before 2nd year but while it cannot distinguish between his and Harry's magic it knows what kind of spell was used. It doesn't notice that Dobby has been using magic to steal Harry's post all summer.
-It doesn't notice hailing the Knight bus before year 3.
-It notices the Patronus Charm before year 5. It doesn't notice the effect of the dementor or at least cannot distinguish between the two.
-Presumably they don't notice accidental magic. Or do they just ignore it? That's kind of weird though because it could go against the Statute of Secrecy. For example, no one came to check upon Lily after she used wandless magic in front of her sister who was a Muggle who did not know about the need for secrecy. (Or do the Obliviators also obliviate the Muggleborn children and we just never found out about them obliviating the Muggles all the time? )

In my opinion this kind of seems more like minors have some sort of area spell around them that notices magic close to them (but only very close) and then notifies the ministry what kind of spell was used. In that case they would probably ignore all notifications in wizard households or wizard areas such as Hogwarts or Diagon Alley. Furthermore, given that they ignore accidental magic AND wand magic before going on the Hogwarts Express for the first time. It would make the most sense for me if they put a potion in the students' drinks during the first and second meal of the year at Hogwarts. Some fiction I read had that explanation.

If they had a widespread method of tracking people the Death Eaters that escaped in book 5 should have been easily captured. In the first war as well.

For the Love of Magic by Noodlehammer actually had an interesting idea here. These kinds of area spells can only permanently be cast if you truly own the area. A monarch for example cast or authorize the spell but it doesn't work for just anyone. That makes the most sense to me because otherwise you could presumably cast a countrywide anti-apparition ward and screw everybody. It's also the reason I dislike the Taboo. I also think that a Taboo on "My Lord" would have been pretty good at getting Voldemort's location whenever he is with his followers. If you can cast something like this why not other countrywide spells? And if they work like the Taboo, then you also cannot just undo them. Otherwise people would just undo the Taboo all the time to annoy the Death Eaters. It simply doesn't really make sense in my opinion.

 

I think you're overlooking paranoia and caution as a factor. It's not that the Ministry was sure to find them if they went into civilization, it's that when risk/reward calculus says there's a 95% chance of getting slightly better food, and a 5% chance of being captured, horribly tortured to death, and effectively dooming Britain to be ruled over by Voldemort for the foreseeable future ... yeah, I'd suck it up and eat the less than perfect food.

Especially since, as I recall, most of their complaints were on account of eating canned food. Getting a lot of stuff that won't spoil is going to be a practical necessity unless they want to make regular trips into civilization to get fresh ingredients. Even if the chance of getting caught on any individual trip is minuscule, the odds will catch up eventually.

Also, if the Ministry has such omniscient tracking and tracing ability, it begs the question of how the Death Eaters ever get to be as much of a threat as they are. Most of the time we see the Ministry's tracking ability come up, it's in the context of them getting things wrong or missing the obvious (Dobby, Sirius Black, the Dementors in OotP, the Azkaban breakout).

For a couple suggestions on how crime isn't as much of a problem...

1: Everyone is armed
Starting from the age of 11, every single wizard has a deadly weapon in the form of their wand. That's going to make a lot of common crimes very risky. Why take the risk of robbing another wizard's house or mugging them for petty cash when you know they could kill with you a wave of their wand and two words?

2: Defensive magic
We know wards are a thing, and some of them like the ones on Hogwarts can be quite potent. I'd imagine most businesses and family homes have fairly potent wards.

3: Forensic/Investigation magic
Canon hasn't gone into this too much, but there are plenty of indications that magical investigators have ways to figure things out after the fact. Things like Priori Incantatum and Veritaserum are very potent tools for figuring out who committed a crime.

4: Muggle-Baiting
One of the least pleasant explanations. Wizarding society is shown to be very tolerant of wizards abusing muggles, as long as they do so in a way that doesn't imperil the statute of secrecy. I expect a lot of the bad elements in Wizarding society just target muggles instead of their fellow wizards, and do enough to cover their tracks. Mind control magic, invisibility, and memory-altering spells give the garden-variety sadists and sociopaths all kinds of tools to abuse the (relatively) helpless muggles. Why take the chance of going after another wizard when you can victimize muggles with practically no risk?

(Also, for some fun paranoia fuel, just think about every time something valuable goes missing, you have an injury and can't remember how you got it, or you can't remember what you did last night. Are you sure this isn't the result of an invisible wizard screwing with you, and then erasing any relevant memories?)

 

Huh I was just browsing another discussion and saw that someone had written this:

"In HBP, we are given probably our best insight into the Trace. When Harry and Dumbledore watch Riddle's meeting with the Gaunts, they end the scene with a discussion on how Tom could have killed the muggle Riddles and framed the Gaunts despite the Trace. Dumbledore states that the Ministry is capable of monitoring magic use, but incapable of determining the offender. In magic-heavy areas, or areas known to be home to active wizards/witches like Little Hangleton near the Gaunt Residence, the Trace is nigh-useless. All it took for Tom to defeat the Trace was to steal a wand, and cast a spell in a residence right next to a wizard's home.

Tom did not use his own wand to cast the spells, but Dumbledore clearly states that the Trace would have detected him using magic anyway, so the Trace's detection is not wand-based. The information gathered by the Trace seems to be categorized geographically, as the Ministry can tell where a spell was cast, but not by whom. It also seems indiscriminate. Even though the Trace would have been on Tom, the Ministry seems unable to determine whose Trace triggers the detection. Strangely, the fact that the Trace picked up a spell in the area was never used as evidence of the presence of an underaged wizard, despite there being no reason for any Trace to trigger in the area with only muggles and adult wizards."

https://forums.darklordpotter.net/threads/pet-peeves-v-11.33743/page-3#post-923886
(Didn't want to quote them and send them a notification for 3 year old post)

I can't actually check whether that's right because my books are not in my apartment here but it makes sense as far as I can tell.

 

I think that the Trace could still be in active on adult wizards, but not monitered. Whether the Trace is placed upon wands, magical beings or areas is up for debate, but I would imagine that the Trace is registered to the wand of any witch or wizard when they purchase it from a licensed wand maker. This would lend credence to the idea of disposable, unregistered wands being used for crime, or by wizards wishing to protect their privacy.
As for the issue of Dobby's levitation charm being picked up as Harry's, I would assume that the ministry either also has some way of tracking unregistered magic in Muggle areas, and that they saw that Harry was the only registered magical being nearby, or Dobby purposefully set of the Trace on Harry's wand. If Draco Malfoy is able to practice magic at home, then it is entirely possible that House Elves and wizards and witches with the know how are capable of altering the Trace.

 

One thing I noticed, is that it was never actually specified that the trace is only on magical children, if its on all children it would in fact give the ministry a huge area where they could detect what magic was used, but would still allow there to be lots of places where criminals could use magic and explain why they cant just catch every criminal. So the Trio for example couldn't just have used magic in a city since there could be children anywhere, which would report their use of magic.

just a reminder of how the Trace seems to work in Canon.

The Trace is a charm that detects magical activity around under-seventeens(according to Moody), but its considered next to impossible to remain after the 17th birthday(Accoding to Ron), the trace reports what kind of magic was used in proximity to the underage person and where it was used, but it doesn't report who used the magic, neither does it report whose trace reported the magic.

This results in the Restriction of Underage Sorcery being unenforceable by the ministry in a magical household, and causes them to rely on parents to make sure their kids dont use magic outside of school(According to Dumbledore).

It also allowed Tom Riddle to get away with using magic to murder his family when he was 16, since the trace wouldn't have told the ministry who used the magic and even that he was nearby when the whole thing happened. He planted further evidence against his uncle by using his wand and altering his memory, but thats irrelevant to the trace.

For the way the trace seems enforced, it looks like they just receive an alteration that a certain piece of magic was cast near an under seventeen year old at a certain location, and then they just look up the local underage wizards and should there be no adult wizards there, it would result in them getting a warning by the ministry.

Thats also why when Dobby's use of magic near Harry, in his home, when he is the only wizard living in the neighborhood, resulted in Harry getting a warning by the ministry.

It would also explain why nobody was alerted by the trace reporting the use of the killing curse when Voldemort killed his family, since their would surely have lived other children there.

And it explains why Wizarding families dont just use the trace to determine if their children are magical or squibs, surely it would have been trivial for Nevilles family to ask Mafalda Hopkirk if their own magic use was reported by the Neville's trace. But if even a squib would have it, it would explain why them knowing this wouldn't help them find out if he's magical.

 

I should say that while I love a good "How does the Trace work?" discussion, the intent of the thread was directed less towards working out how the Ministry monitors magic in canon (about which we have very little info) and more at how in fanfiction you would choose to depict it.

 

One problem with your basic thesis @Taure is that we don't know how big or full Azkaban actually is. So we don't know how law abiding society is, or how effective the Ministry is at catching criminals.

I do like the idea mentioned above that most wizards probably commit their crimes against muggles, and get away with it. Those sorts of crimes probably only get noticed if you are stupid enough to talk about them in public, or if you do something else which brings the Ministries attention onto you.

Personally if I was writing a fic, and its a bit of a cliche, I'd use the idea of some sort of rune stone network across the country. It would allow the Ministry to anchor spells to affect the entire country. So they could monitor magic that way. I'd probably not make it perfect. Perhaps its a bit like phone masts, so the more rune stones there are the stronger the signal but for budgetary reasons they have a looser network than would be ideal. So in sparsely populated areas they get very basic coverage, and in the centre of London they get detail.

As to what detail they get...I think I'd probably write it that at its best coverage the map could list a fairly precise location, a rough classification of the power of the spell (though this would necessitate a debate on how the power of magic could be quantified), or at least whether it was a charm, jinx, hex, or curse etc. And then perhaps some sort of anomalous but potentially useful detail like the core of the wand that cast the spell, almost like that flavours the magic a bit. So in areas with worse coverage they probably only get very rough location. Perhaps the map system would use triangulation from the nearest 3 rune stones, but there is a maximum range on how far away the rune stones can be. So in the worst covered areas they maybe only get location based on 2 or even 1 rune stone.

 

As protecting the Statute of Secrecy is arguably the raison d'être for the Ministry of Magic, I could see magic tracking in muggle areas being the objective of multiple departments, each with different means, that as a whole would make a pretty tight net. So here are some ideas for those:

Maps: I like them, but they run the risk of being too good at their jobs. To balance that, I would limit them to major cities and only display where magic was used, with personnel apparating there for more in depth investigation and, if necessary, obliviation/apprehension. Maybe they would get more imprecise the less they reflect reality, so the department responsible has to keep up with the city planning and constantly update their maps (which may be more laborious than just redrawing). Thus they routinely partake in nudging the muggle government away from large scale development in order to make their jobs easier.

Divination: This is can be a tricky one, both Rowing and fanfic authors tend to stay away from this aside from The Prophecy for good reason, but I like when it's used in a non-OP way. Given that the DoM has approximately a shitload of prophecy balls, I don't think that people with talent in the area are that rare. Since Divination seems to be rather unreliable and irregular, instead of a dedicated department the Ministry would offer bounties for predictions, with a pool of trusted Seers whose warnings are more readily followed. And, so not to make too easy for law enforcement, prepared individuals may have means to dodge all but the more powerful auguries, by means of a spell or potion or artifact.

Arithmancy: My headcanon (or personal fanon?) is that Arithmancy, while more reliable than other forms than Divination, is not very good at predicting the future. Still it can be used to find places or wizards of relevancy after/during the act, which can be further narrowed down through more maths or regular investigation. So, somewhere in the Ministry there is a bunch of nerds constantly crunching numbers in order to find anything or anyone out of line, a possible career path for an alternate Hermione.

To clarify, in my definition of Arithmancy, one would basically "ask questions" using equations (with different equations for different questions), by inserting two types of variables, one to add the parameters and another being randomly generated numbers so the magic works out. The result of the calculation would be the answer, the accuracy of which vary on a series of factors (e.g. choice of equation, competency of the Arithmancer). Like Divination proper, may be subject to countermeasures.

Animals: Taure's idea is neat but a bit broad and vague as it is. All animals being secretly Ministry snitches is a bit much to my tastes. Maybe they have a fleet of carefully trained pigeons that do the spying, they blend well and have quite the good eyesight. Intelligence and magical capabilities are already present in Owls, perhaps just by raising animals wizards make them more in some ways. Aside from regular critters, many magical creatures are already attracted to wizarding homes, suggesting some form of magic tracking from them. If there is a creature with a perception that is wide and sensitive enough, the Ministry would likely make use of them. So, insert quirky original magical beastie here.

Inquisitors: These guys would be the more proactive sort. They would shadow, investigate and check on people that are "at risk" of breaking the statute, how invasive/annoying they are would depend on how much the Ministry would like the investigated to change their ways. Wizards whose private business involve dealing with muggles would be scrutinized for the tiniest fineable offense, muggleborn's families might be interviewed every now and then, etc. It's probably a job ripe for anti-muggleborn abuse as well as one of the means to discourage fraternization with muggles.

 

The only thing the ministry needs to monitor is Taure’s LEGO collection.