We have this player in our group that took the Alert feat and at the moment he is claiming that with the feat he is also alert for traps like pitfalls or even traps that he hasnt seen where they are. Pretty much he is saying that even if he didn't know the trap was there and he stands in the middle of it his feat allows him to completely evade the trap without even needing to make a saving throw. We are newer to the game and i havent found a complete answer to this online so i would like to ask it here.

How would you rule this situation because the person that does this is someone that is a player that questions the DM's choices and rulings because he has played the game abit more then the rest of us so we are in need of some complete proof that what he says is true or not. Please let me know :)

Alert

Always on the lookout for danger, you gain the following benefits:

• You gain a +5 bonus to initiative.
• You can't be surprised while you are conscious.
• Other creatures don’t gain advantage on attack rolls against you as a result of being unseen by you.

Alert does nothing whatsoever for trap detection.

Surprise

A band of adventurers sneaks up on a bandit camp, springing from the trees to attack them. A gelatinous cube glides down a dungeon passage, unnoticed by the adventurers until the cube engulfs one of them. In these situations, one side of the battle gains surprise over the other.

The DM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter.

If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. A member of a group can be surprised even if the other members aren't.

Are they perhaps confusing Alert with Dungeon Delver?

Dungeon Delver

Alert to the hidden traps and secret doors found in many dungeons, you gain the following benefits:

• You have advantage on Wisdom (Perception) and Intelligence (Investigation) checks made to detect the presence of secret doors.
• You have advantage on saving throws made to avoid or resist traps.
• You have resistance to the damage dealt by traps.
• Traveling at a fast pace doesn't impose the normal −5 penalty on your passive Wisdom (Perception) score.

Does that mean that when he falls into a trap the Alert feat gives him no benefit in evading or his saving throws he would have to make?

The feat only does what it says it does - nothing more.

If the player wanted protection from traps they should have taken the Dungeon Delver feat instead (or as well).

Quote from Dragonmach >>

Does that mean that when he falls into a trap the Alert feat gives him no benefit in evading or his saving throws he would have to make?

 Correct.

If they are a Barbarian however, Danger Sense would help them.

Danger Sense

At 2nd level, you gain an uncanny sense of when things nearby aren’t as they should be, giving you an edge when you dodge away from danger.

You have advantage on Dexterity saving throws against effects that you can see, such as traps and spells. To gain this benefit, you can’t be blinded, deafened, or incapacitated.

Quote from Dragonmach >>

Does that mean that when he falls into a trap the Alert feat gives him no benefit in evading or his saving throws he would have to make?

 Did they intend to take the Dungeon Delver feat instead?

No the person is actually playing a barbarian but the only thing he said is that the alert feat makes him always lookout for danger so he wanted a boost to his dex save because his alert feat would let him not be surprised by the trap and have him react faster to the trap. He didnt mention anything about Danger Sense and only talked about the alert feat.

Quote from Dragonmach >>

No the person is actually playing a barbarian but the only thing he said is that the alert feat makes him always lookout for danger so he wanted a boost to his dex save because his alert feat would let him not be surprised by the trap and have him react faster to the trap. He didnt mention anything about Danger Sense and only talked about the alert feat.

 Then there are two possibilities:

1. They got the benefits of the feat and the benefits of their class feature confused. No biggie, happens all the time.
2. They are mistaken and you can direct them to this thread if they do not believe you when you tell them that. 

The “surprise” mentioned by the Alert feat is in reference to the rules for Surprise (which I pasted into my first post for you) and only to that situation.

Quote from Dragonmach >>

No the person is actually playing a barbarian but the only thing he said is that the alert feat makes him always lookout for danger so he wanted a boost to his dex save because his alert feat would let him not be surprised by the trap and have him react faster to the trap. He didnt mention anything about Danger Sense and only talked about the alert feat.

 
Then he is using the feat wrong and not understanding surprise rules.

Thank you for the info and the fast response, we will tell him about this and hope that the situation will be fixed now we know this. Thanks again!

Quote from Dragonmach >>

Thank you for the info and the fast response, we will tell him about this and hope that the situation will be fixed now we know this. Thanks again!

 Happy to help. I mean, worse comes to worse maybe a feat swap is in order. You’re all new, mistakes get made. I have been playing D&D for decades across multiple editions. I probably get more stuff confused than you will because I have a noggin full of outdated rules with mostly the same names. 🤷‍♂️

Well at the moment he was asking if he could feat swap because barbarians get pretty much the same perks with their class. At the moment our DM has decided to not allow him to do it only because he wants this person to reflect on it. I do understand it sucks alot but at the moment this person is metagaming abit and is trying to get every single little bonus he can get from every situation so it was decided that he was not allowed to change it. Ofcourse that also means anyopne else can't change anything aswell but unlike him most of us have already made a level 20 version of the character that we are playing and have thought a little about what we would do with our characters. So we choose this to be a good moment for him to understand that he cannot decide on his feat choices and other stuff so easely. 

Ofcourse it sounds abit harsh because most of us are pretty new to the game but we are trying to do everything as close to the main rules as possible and our dm doesnt want to allow to much because it would maybe change the way how we would play d&d then other people.

Still he did allow a few things like funny magic items or pets. At the moment we are almost competing who has the better pets and we are loving it. The reason our DM allowed some of the overpowered pets is because we had 2 front line fighters that couldn't be there alot of the time with one of them stopping because he was to busy. So we only had a barbarian that could tank and sometimes every 4 to 5 sessions we would have our paladin joining us so the DM tryed to get us abit more support in the form of pets that could take some hits for the team.

I myself play a Necromancer as my first character that has been forced on the path of necromancy by a strange object that gives of Necromantic energy. I had a pet squirrel and when i was in a roleplaying moment with the object my squirrel started to be affected by the necromantic energy and started to mutate, now i have a wraith squirrel with the intelegence and wisdom of a normal squirrel but the other stats and ability's of a wraith.

One of the other player is a warforged artificer that took the path of an artillerist. He has a sentient magic item as a pet in the form of a cat but once every week it can transform into a T-Rex and help us in battle. In cat form the cat only has the same health as the T-Rex but only deals 1 damage with attacks.

Then we have our last player that has pets and he is a bit of an odd one, his character died really early in the campaign because of some shitty roles and him trying to cross a river that let to a waterfall that let towards the underdark. He needed alot of saves to be able to get across to scare him in not crossing the river but he still did and he fell into the river. After that we tried to save him and almost an hour of rolling later because every fail would let him to the edge of the waterfall again he eventually fell from almost surface level straight into the underdark making a few mile drop down. He didnt insta die because litterely almost all the damage die that he took where nat 1's so he had to make his death saving throws which he eventually crit failed untill he died. Afterwards our DM was abit guilty because of the shitty way he had to die so he was allowed to play a pretty balanced Homebrew class called the Eidolist. Now as an Eidolist he is taking as many summoning spells as he can and together with his mutating avatar he is the third pet collecter of the group.

Well, at least that PC who has Alert can’t be Surprised anymore. The next time the DM ambushes your party with goblins/bandits whatever that PC will be able to act on the first turn of combat while the rest of you have to wait until the second round before you can do anything.

i have a similar issue where he wants me (the dm) to tell him if there is a trap down every hallway we come to i dont know the exact name of his ability and this is my first time being dm so i dont know much about it, i made the dungeon with lots of traps not knowing of this ability but every trap has a way to escape

You don't have to tell your player if there's a trap in every hallway, you can note the character's Passive  Wisdom (Perception) and Intelligence (Investigation) scores and if a trap is detected you can say so. Otherwise, the character can always search for one.

Quote from mnmnmnmnmnmn >>

i have a similar issue where he wants me (the dm) to tell him if there is a trap down every hallway we come to i dont know the exact name of his ability and this is my first time being dm so i dont know much about it, i made the dungeon with lots of traps not knowing of this ability but every trap has a way to escape

 Ask the player what ability he thinks allows him to do this and read it, the rules are fairly clear when looking at a single ability (there can be confusion when looking at how two ability interact) probably one of the following is the case:

• They have looked at the flavor text and has turned it into a mechanic (As above "always on the lookout for danger" says nothing about always spotting traps but some people might wish it implies it.
• The player had not read the actual ability but what someone (mistakenly) said about it
• They stretch the wording to something clearly not intended (and usually not correct) an example of this is to claim that the lungs are an "open container" and therefore create and destroy water can flood their lungs causing them to drawn.

Features do exactly what they say, no more no less.