Does the caster of Dispel Magic know if they are successful?

Question

Upon reading the text of Dispel Magic it isn't clear to me whether or not the caster of Dispel Magic knows whether or not they have been successful at dispelling a higher level effect. Or even if there is a higher level effect.

In particular the caster needs to

For each spell of 4th level or higher on the target, make an ability check using your spellcasting ability. The DC equals 10 + the spell''s level. On a successful check, the spell ends.

So because of this ability check, the caster seems like they might know about whether they have succeeded at the spell or not (just like a rogue knows they succeeded at their ability check to pick a lock for example).

So does the caster know if they have successfully dispelled a spell/magical effect (for these or any other reasons)?

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This is related to, but distinct from, this question because my question is unconcerned about saves or immunity specifically.

Answer 1

No, the caster doesn't know if they succeed or not.

The rules do not provide any special kind of feedback for spellcasters to be able to tell if they are successful or not. If you can't perceive the spell's success (or lack thereof) using your normal abilities and/or senses (eg seeing the eruption from fireball, feeling the tremor of earthquake, etc.), then you cannot determine the end result.

This applies to every spell for any possible failure reason — there simply is, according to the rules, no way for this to happen.

The ability check makes no difference

You specifically mention the ability check of dispel magic as a reason for the caster to know if it failed or not, but this doesn't have any effect on your ability to tell if you succeed or not. The example of a rogue using am ability check to open a lock is a good example of an ability check with an observable result (you can see/hear/feel the lock). However, there are many examples of ability checks that you can't necessarily tell if you failed.

For example, if you roll investigation to figure out how a trap works and roll low, you character can still even think they have succeeded and end up trying to disarm the trap the wrong way. Failing a perception check just means you don't notice anything. Not noticing things is ambiguous if you have passed or failed — there might be nothing in the room or you might have just not beaten the DC for the army of ninjas on the ceiling.

All this is to say that nothing about the ability check in dispel magic necessarily gives the caster any insight into their spell succeeding or not. We don't even really know what the ability check represents in-fiction (if anything).

Unless the caster can detect the results using their senses, there is no way for the caster to know if their dispel magic succeeded or failed.

As always, of course, if your DM wants to create a homebrew mechanic for spellcasters to be able to do this, they are more than able to do so.

Answer 2

Characters know when they fail an ability check

What is an ability check?

The DMG tells us:

An ability check is a test to see whether a character succeeds at a task that he or she has decided to attempt.

The PHB gives us the following guidance:

An ability check tests a character's or monster's innate talent and training in an effort to overcome a challenge. The DM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure. When the outcome is uncertain, the dice determine the results.

As a result an ability check is a measure of a character attempting to succeed at a given task or challenge. In order for someone to attempt to succeed at a challenge or a task, you have to know the task is available to be attempted.

Does a character know they failed a check?

Yes.

The PHB gives us the following details on the mechanics of a check:

If the total equals or exceeds the DC, the ability check is a success — the creature overcomes the challenge at hand. Otherwise, it's a failure, which means the character or monster makes no progress toward the objective or makes progress combined with a setback determined by the DM.

In addition the DMG gives guidelines on trying a check multiple times (which requires the knowledge that you have failed):

Multiple Ability Checks

Sometimes a character fails an ability check and wants to try again. In some cases, a character is free to do so; the only real cost is the time it takes. [...] However, no amount of repeating the check allows a character to turn an impossible task into a successful one.

In other cases, failing an ability check makes it impossible to make the same check to do the same thing again. [...] But you might decide that the initial failure makes those checks more difficult to pull off.

Both of these passages, particularly the multiple ability checks passage, make it clear that characters know when they fail at something they have attempted.

But surely there are situations where a character doesn't know they have failed a check?

Of course there are. For these situations the PHB provides:

Passive Checks

A passive check is a special kind of ability check that doesn't involve any die rolls. [...] or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster.

How does this apply to Dispel Magic?

The checks in Dispel Magic are clearly active checks as they involve a die roll. In active checks the character will know if they have succeeded or failed. As a result they know that they have succeeded or failed for each time they have to make this check.