Would this be a good boss for 5 level 1's, I just want peoples opinions on this topic.

Quote from Smokehorn >>

Would this be a good boss for 5 level 1's, I just want peoples opinions on this topic.

 Absolutely not. He can kill, not just knock out, straight up kill 2 party members a turn if they're unlucky, wouldn't even need to crit.  You'd want something more along the lines of an ogre, tweak it if you need to, but not  this beefy boy.

Quote from NoidedYungDM >>

Would one Hill Giant be good for a party of 5-6 3rd and 4th level characters or should I pump the difficulty a bit?

 It's close. It can potentially down two people in a row, or instakill a wounded and/or squishy character with a crit or high damage roll. But then again if they play smart, they might destroy him utterly. A couple command spells or rays of enfeeblement, good use of a Barbarian, and he could become a cakewalk. But MOST worthy bosses can become a cakewalk with good luck and effective strategy, so don't go thinking this guy's not a suitable challenge. But if you want something similar but a bit less DEADLY you could look at the Ettin, perhaps beefed up in health, and/or after fighting some fodder. 

a fifth level ranger in my game kinda killed a hill giant in a one v one, so maybe just don't let them keep a good distance away

we have no rangers in my party but we do have a cleric with a bow. it's ok if they take it out easily, i just needed somwthing decent but still small. thanks for the help!

Dragons hate all Giant species. They've been at war for millennia. It's actually mentioned in Storm King's Thunder.

hi

I feel like they call them Hill Giant because Hillbilly Giant didn't fit on the base of the figurine, poor guys.

On the other hand, maybe they wouldn't be evil if they knew better (they are evil because evil is easy to understand)... that -3 to their already abysmal INT score seems like a hit below the belt at this point.

So handsome

The hill giant has poorer mental statistics (Lower Int, Wis, and Cha) than an Ape, and yet the ape is unaligned while the hill giant is chaotic evil. I've always wondered at that.

For some reason the SSI game; Champions of Krynn loved pairing these guys up with mobs of goblins.

It's all about disposition. And alignment just being a descriptor, not set in stone. It doesn't take mental stats to be good or evil. Abyssal Chickens are evil and have even lower mental stats.  Abyssal Wretches, too. There are plenty of other examples. 

Quote from murfALISHIS >>

is a hill giant a godd mini-boss for 6th level players. i'm a new dungeon master.

 I am a player and I agree

your not wrong :)

A Hill Giant has Darkvision. Right? Variations of the Hill Giant, e.g. Hill Giant Sargent, Hill Giant Servant, Young Hill Giant all have Darkvision.  But it's not listed above. Do they develop a case of cataracts that take away their Darkvision later in life?  LOL!  

Quick note: Looks like the issue is not with D&D Beyond rules. I noticed the issue in purchased 5e material on Roll20 specifically  in the adventure, Against the Giants from Tales from the Yawning Portal.  The variant giants I mentioned earlier have suggested stats of other creatures, like Hill Giant Servant should use Ogre stats. In Roll20 they kept the the Ogre's darkvision sense in the statics for the Hill Giant Servant, thus my confusion, and not an issue with D&D Beyond. For those who use Roll20 it's something that has to be corrected. 

Would it be possible to somewhat nerf this giant for a party of level 3s or 4s?

Throw an ogre at them

to answer the boulder question, set the encounter in a rocky area, like this plains and hills with many boulders - Bing images  to make it realistic, perhaps have the hill giant spend some movement to find and pick up a rock to throw it, though i adore your boulders magically appearing solution, you can totally go for that if your playing in a very high fantasy setting. 

  belts of giants strength don't need to come from giants, though they can if you want them to. it could be worn by humanoid champion, warlord or bandit leader. the belt is a bit powerful for level 5 in my opinion, perhaps the Gauntlets of Ogre Power for a strength of 19 instead of 21 at level 5. or for even a minor buff the manual of Gainful exercise is a good option. I only suggest these alternatives as, as you mentioned, your a first time DM, and balancing can be tricky, though granting your cleric an above average hit rate on their mace SHOULD be alright as they only do a d6 damage. 

Crazy powerful 

Quote from GEDoom >>

Damn he thicc, that's a thicc ass boi!

 Defending champion of thicc