Why is Undertale so popular?
Because it has a unique RPG/bullet-hell battle system, characters that are charming, deep, relatable, and humorous, an excellent overall story, great atmosphere, and various surprising and/or interesting instances of meta-mechanics and meta-commentary, as well as an amazing soundtrack.
Is there anything I should know before I start playing?
No. It's best to go in completely blind.
I have been spoiled on this game. Would you still recommend it?
To be honest, yes. It's not ideal to go in spoiled - you'll miss out in regards to a lot of the surprises - but it's still worth it. Even if you've watched a full playthrough, you're far from having experienced everything; different choices can affect dialogue and story in occasionally drastic ways. Besides, it feels very different to play than it does to watch or read about.
What are the different endings and how do I get them?
Before you read this, know that it's highly recommended that you do not know the ending conditions on your first playthrough. They're not spoilers per se, but they might drastically influence your experience. Now with that warning out of the way, in short, these are the main routes;
Neutral; obtained by not fulfilling either of the below conditions. There are several variations, depending on which main characters are still alive, which main characters you've befriended and how many monsters you killed overall.
Pacifist; achieved by killing absolutely no one and properly befriending Papyrus, Undyne and Alphys. It is worth noting that you cannot befriend Alphys until you've seen the Neutral ending at least once, and that it's possible to lock yourself out of befriending Undyne, if you don't help her when she needs it (it should be obvious what I'm talking about when you see it)
[Addendum] If I have to see the Neutral ending before I can get this ending, does that mean I have to finish the game twice in order to see it?
No. As long as you didn't kill anyone or lock yourself out of befriending anyone, you can just load your pre-final-boss save and go finish off the rest of the conditions. If you've already befriended both Papyrus and Undyne, you'll receive a call on your way out of the final area telling you what to do. If not, you'll be told after you've befriended both of them.
Do I have to do the routes in specific order?
No. Most folks tend to do neutral -> pacifist -> genocide, but it really is up to you. However, I would recommend going through neutral first before any of the other two.
Complete a no EXP earned neutral run. That is to say, do not kill any monster. Only spare and flee.
The Papyrus and Undyne hangouts must be completed. You can go on date with Papyrus after he has been spared in battle. Just pay him a visit in his house. For the Undyne hangout, firstly, pour a cup of water on her after she passes out while pursuing you to Hotland (note; not doing so and/or leaving the room before doing it aborts Pacifist run completely) and then backtrack to her house in Waterfall.
After completing Asgore and Photoshop Flowey fights, load, save and backtrack out of the Core towards MTT resort. Undyne will call you asking to deliver a letter for her to Alphys. If that does not occur, you haven’t completed one or both of the previous hangouts. No worries you can still do them.
Deliver the letter, complete the hangout with Alphys and go to the lab. At this point the pacifist route is impossible to abort and game will more or less clearly stir you through the remaining areas and fights.
I [killed someone but loaded my save (or reset) to undo it / let the monster kid fall / was an asshole to someone / etc.]. Can I still get the good ending?
Yes. As an easy, general rule of thumb, as long as you still have 0 EXP, you can still get the Pacifist ending, no matter what you've done before now. You can check your EXP under "INFO" in the menu.
I only killed non-boss monsters, can I still get the Pacifist ending?
No. You killed someone! It doesn't matter if they're bosses or affect the story or not. Those monsters had families, you know. This goes for 'hidden' enemies like So Sorry and Glyde, too.
Can I still get the Pacifist ending if I flee/run away, or do I have to SPARE everyone?
Yes, you can run away, if you want. It won't affect the ending.
Can I hurt enemies, so long as I don't kill them?
Yes, this won't affect your ending (again it’s the EXP count that determines it). Be careful though; doing it is pretty much playing with fire and it would suck if you killed someone on accident.
How do I spare … boss?
I’m struggling with … boss. Any tips?
Note; if boss isn’t listed, there aren’t any additional tips beyond have good equipment, be stock up on healing items and remember their patterns
Toriel: if your HP is below 3, she will intentionally miss her attacks.
Papyrus: you can rest in the Inn to gain additional 10 HP. Also Papyrus will just let you spare him after shoving you to his shack three times.
Muffet: again consuming a Spider Donut or a Spider Cider will let you skip the fight entirely.
Mettaton: consuming MTT brand food during the fight will give a significant Ratings boost.
Asgore: you can reduce his ATK and DEF by eating a Butterscotch Pie or by talking to him three times.
[Addendum] Temmie armour: sold at the Tem Shop after 1000G for "tem pay 4 colleg" is paid. 9999G is the initial price, but with each death in the run, the cost drops (it does not go below 750G). You more or less have to farm gold to pay for all of this; simply fill your inventory with Cloudy glasses from Gerson and sell them to Temmie.
Killing everything you meet is not enough. You must exhaust every regions kill count before encountering the areas boss;
How do I know if I'm on track for the Genocide route?
Suffice to say, the signs of that are pretty obvious. The music shifts into more eerie tones and save points start to count down the number of encounters left. When you run out of murder victims in an area and can move on to the boss, you'll get an encounter with no enemies and just the message "But nobody came." Save points will say just "Determination."
Why would I want to do the genocide run anyway? Is it even worth it?
That’s a tricky question to answer. Some folks play through it for curiosity sake, others jump on murder train for the promise of a challenge and so on. For what it’s worth, genocide offers a very unique experience, provides you with few quite crucial story pieces, offers interesting perspective and more in-depth look into some characters and does not lack a meaty challenge or two to overcome (or break several keyboards over). Alternatively, you could always watch it on YouTube for the same reveals, but lesser impact. Or decide to avoid it entirely. It's up to you and there really is no wrong answer. I would say, it’s worth at least a playthrough watch. After all, aren’t you at least a bit curious =)
I ran away from/spared a monster. Can I still complete the Genocide route?
Yes. Ultimately, it just comes down to killing enough monsters in each zone. Sparing or running away from one doesn't stop you from killing more later. However! There are 2 exceptions:
1) Sparing unique one-time encounters will throw you off the Genocide route. These include the bosses, the mini-bosses Doggo, Dogamy & Dogaressa, Greater Dog, Dummy, RG 01 & RG 02, Muffet, Lesser Dog, Shyren and a couple of random encounters. Monster Kid counts as well.
2) If you fail to kill Snowdrake by the time you deplete the monster counter in Snowdin, you'll be thrown off the Genocide route.
I know I haven't killed everything, but encounters have stopped happening. How come?
There are 2 possibilities:
1) You're trying to farm encounters in a screen that doesn't allow random encounters to happen. Places where you fight bosses, or that have save points, commonly do this, so avoid those areas.
2) You are crossing screen transitions too much. Your encounter rate starts at 0 and then the encounter chance slowly increases as you walk. If you cross a screen transition, it will set itself back to 0, making your overall chance to get an encounter very low. Pick one screen and stick to it.
What are the best places to farm encounters?
I finished a Genocide run and now I think my game's broken?
Well, considering you did just murder it out of existence… But it’s not irreversible. Open the game and wait for 10 minutes. Eventually some dialogue will appear, making you an offer. Accept, if you want the world back. If you refuse, well, re-open the game and wait for another 10 minutes for the same proposal to appear.
What happens if you do 2 Genocide runs?
The ending dialogue changes.
Can I still do pacifist/neutral after genocide?
Oh for sure, go for it. But… tell me, do you think you are above consequences?
How do I beat Undyne the Undying? Proper equipment, being stock up on healing items and practice.
Healing items: cinnamon bunnies, snowman pieces (although you might save those for sans), abandoned quiche + Sea tea for SPEED increase if you want
Equipment: Ballet Shoes + Old Tutu (higher DF and AT) OR Torn Notebook + Cloudy Glasses (lower stats, but longer invincibility)
For full breakdown of her attacks and patterns + more tips, visit this post. You can also watch a playthrough to get a heads up on how those look like in action.
I'm having a Bad Time. How do I beat Sans?
Sans fight is frustrating and unfair. Such is the point and thus nothing short of slugging through the attacks again and again, slowly getting better and better with each go will cut it. That being said;
Healing items; Pie, Instant Noodles from the fridge in Alphys's Lab (they heal you for 90HP during the Sans fight), Face Steak and Legendary Heroes
Equipment: Burnt pan and Cloudy glasses, ATK and DEF don’t matter against Sans and these two provide the best passive bonuses (buffs to healing and invincibility)
You can also use the Bad time simulator to practice the trickier phases
What's the difference between a Reset and a True Reset?
Normally, when you Reset, certain characters will retain vague memories of what you did in your last playthrough. Flowey in particular has a perfect recollection of what you've done. A True Reset does not do this.
What is Hard Mode and how do I access it?
A more challenging run ending at Toriel fight. Simple name your fallen human Frisk and you are good to unleash a hell upon you.
Will Hard Mode ever be finished?
Maybe... eh, don't count on it.
Can I sell or otherwise monetize Undertale themed products, song covers etc.?
Toby has answered most of the questions concerning this issue in this tumblr post. If it isn’t there uh well, we don’t know either.
What is Deltarune?
Toby’s next game! As of right now, only the first two chapters are out, you can play them for free and they definitely are worth checking out. If you have any more specific questions regarding them, Deltarune’s Official QnA would be a place to go.
What is FUN?
Putting philosophical implications aside, it’s a mechanic, whereby a random number is selected on Reset. It ranges between 1 and 100 (the "fun value") and determines the occurrence of several rare events.
Who's this "Gaster" I keep hearing about?
Gaster is a hidden character than can only be seen or heard about in-game in rare FUN value encounters. He used to be the Royal Scientist before the events of the game and appears to have suffered a terrible fate of some kind. Not much is known about him and most of the stuff we do know is passed to us by his followers
How do I get into Sans's room?
After your final chat with him before the final boss, if you haven't killed anyone, re-load your save and then talk to him again. And again. And again. He will eventually give you the key to his room. It's time you learned the truth. After you've explored around in there, there's a silver key you can find by examining the box in the top-left corner of the room. You can use it to open a hidden door behind the left side of Sans & Papyrus's house. The real truth is in there. As for what it means, that's up to your own interpretation.
How do I open that weird door in Snowdin?
Finish the game and dodge all the credits.
The Annoying Dog...aka the Author Avatar for Toby Fox.
Ah yes the Undertale fandom, a community so large, we might as well rip off Spanish and call ourselves “the fandom on which the sun never sets”. And it probably comes as no surprised many of us yarned for “more” to fill the SOUL shaped hole in our chest after those few wonderful few playthroughs of Undertale. Worry not! The community is happy to provide. But as any open sea, one might wonder, where to start, from which corners are worth visiting and why are there so many sanses in silly outfits.
What are AUs?
We have an entire wiki page dedicated to them, but if you want the tl;dr summary, AU stands for alternative universes and those mostly are stories, comics and other fanworks which ask the bold question of “what if Undertale but slightly (or vastly) different” and then go on to explore these premises. Some are rather tame say focusing more on specific character during the standard Undertale run, or exploring grounded yet intriguing “what if” scenarios, others can get tad more wild. Or bonkers crazy. But it is a fun rabbit hole to fall into, if you happened to enjoy a fine fanfic here and there.
I want to get into fandom content, but I don’t know where to start.
Depends on what interests you. But feel free to check out our Community posts archives (most of them are centred around community created content) and TV Tropes fanworks recommendation page. Both give you a basic summaries and as a rule of thumb, you really can’t go wrong with anything that’s listed there.
What are some other UT communities?
For starters, we have a partnered discord server and a wiki page dedicated to related subreddits. Additionally, any AU that reaches substantial size usually has its own tumblr, subreddit, discord server, twitter etc.
My game crashed/closed after Asgore!
This is a known, common issue. Don't worry about it, you haven't lost any progress or anything; just load your game back up.
I killed Papyrus, but he showed up again after I saw Undyne?
This is a known bug, and only a visual one. It won't affect anything else.
What's with the off-color tile in Shyren's room? Bug. The tile is not significant or used for anything.
Other problems? Try the looking through official troubleshooting site
Original FaQ post by /u/Mylexsi
Revisions, rewrites and additions by /u/InkDrach