The first thing you need to know is that if you haven't beaten sans before, you might as well not try to no hit Sans. Now that that's out of the way, here's a guide for a little bit of preparation.

Food
Because we will not be healing at all, the food that you currently own doesn't matter at all.
Sea tea is the only thing that might affect your gameplay, as it speeds you up during the fight making it easier to dodge Sans's attacks. However, sea tea can throw you off because it will change the speed of your heart, sort of like how mouse acceleration can be helpful to move the mouse around the screen but not for pinpoint mouse accuracy.

Weapons
The weapon you have doesn't matter either, because you will always one-shot Sans at the very end of the battle, and you will always miss before the final attack.
It is recommended to have a weapon that only has one attack "bar" to time, because it can help speed up the process of dying many many times.

Other Preparations
That's all you can do beforehand, other than making sure you actually are in genocide (because I've accidentally spared bosses then saved during genocides). Make sure you keep an open mind as to if you should quit. Mentally preparing yourself for hours of failure is a good idea, unless you have a hundred hours in the game already.

Attack 1
Sans's first attack is relatively easy after a while because of the numerous restarts required past that point. If you're having trouble, take your hands off of the left and right arrows and focus on moving up and down for both attacks.

Attack 2 - Jump Rope
Jumping up and down at a constant rate shouldn't be too hard. Make sure you are consistent at this part; there's a harder version of it later.

Attack 3 - The Middle Finger
This is the first one people have trouble with consistently. For the first half of the attack going left, tap both left arrow key and up arrow key at the same time and let go at the same time; you should make it with room to spare. Going right, I like to tap jump then hold right arrow key all the way; you have more horizontal room to maneuver going right because it goes from edge to edge (instead of middle to edge going left).

Attack 4 - High Jump Rope
Make sure you time your jumps right, a lot of this comes down to intuition. There's quite a few pixels at the top of each bone and a few at the bottom of each bone where your heart can clip into the bone and it won't count as a hit; if you learn where those are it will help you decide when to release jump.

Attack 5 - Left Mario
This one is quite simple. Memorize the patterns first couple of times through and you'll get it easy from there.

Attack 6 - Right Mario
This one is also just a little memorization, easy to get after a while. When going down from the 4th to the 5th platform, don't jump, just hold right arrow key and you'll land on the platform.

Attack 7 - Donkey Kong Bone Blast
For this attack, try to stay at the bottom of the screen, jumping above to the 2nd platform only when needed. If you're on the 2nd platform and you need to go towards the right quickly, tap the jump button while holding right so the conveyor doesn't slow you down.

Attack 8 - First Bone Tunnel
The two bone tunnels will always have the exact same attack pattern, so once you learn a strategy for them, you can use them every single run. I like to jump over the first wall and quickly move to the far right of the platform before passing the 2nd wall, so the center of mass of the heart is floating, but the left side of the heart is still above the platform (see image above). If you do it this way, you don't have to touch the keyboard until you move left. Going left, after passing two walls, (just staying on the right, you literally don't have to do anything) jump straight up in the air and the attack will end before you can hit the ground.

Attack 9 - Horizontal Blasters
For this attack, stick to the bottom right of the screen. If a blaster aims the bottom layer, jump up, and then jump back down and go towards the right once it's safe. There will never be 2 blasters attacking at the same time.

Attack 10 - Second Bone Tunnel
This was one of the harder ones for me. Again, the two bone tunnels have the exact same attack pattern every time, so once you get a dodge pattern, stick with it. Going right, I jumped the first wall, and then stuck as far left on the platform as I could to dodge the second wall and the third wall. Going left, I could just relax until the last wall which I just skipped by jumping straight up again after the second wall. For some reason, either the platform's hitbox or the heart's hitbox is a little jank so that it's easier to fall of the platform on the left side than the right side, so be cautious if you intend to stick to the left of the platform.

Attack 11 - Speedy Jump Rope
Again, make sure you have a groove going, this attack shouldn't be too hard, just tap up slightly faster than the first one.

Attack 12 - Conveyor
For this attack, it seems like you should be jumping them one at a time, but that usually doesn't work out; A much easier way is to wait until the lower row of bones almost hits you, then jumping as far left as possible. You should land in between two bones, then slowly make your way towards the right. Tapping the right arrow key is the best way to do this, because (like in Skyrim), your movement speed is just faster than the bones. Once you hit the right wall, I just jump up because if you timed it right, there will be no more bones coming from the upper potion.

Attack 13 - Speedy High Jump Rope
Another one of these, just slightly harder. It's nothing new, so once you nail this one, we're off to the second half of the battle.

What You Should Be Doing

You know what to do at this point:
literally nothing.

Drink a Sea Tea if that's your style. Crack your knuckles, or go get a drink of water. You know what to do next. (It's not sparing him, in case you're confused).

The meta bones are bones that can and will catch you off guard and take away that precious health throughout the second half of the fight. In order to dodge every iteration of the meta bones, just press right over to act, wait a second, and then press left again back to fight and spam select. This way, you'll dodge all the meta bones, nobody gets hurt, and everything will be alright.

The second half of this fight is a heckuva lot harder than the first half.

Attack 1 - Dimensional Rift
This attack will appear all throughout the second half, so it is best to familiarize yourself with the numerous iterations so that you aren't caught off guard.

Possible DR Attacks:

• Jump Rope
  
• Direct Jump Up
  
• High Jump Rope
  
• Long Jump - For this attack, it will always be moving towards the left. So as soon as you see it coming, hold up, then as soon as you clear above, hold right. If you are having trouble or if it's a tight squeeze, tap the left arrow to press yourself against the wall first (as you are going up) to have a little more room to work with.

Attack 2 - Small Blasters
This is the small version of this attack. Some people have trouble with dealing with it, but a trick is that there will always only be 1 blaster firing at a time. In order to deal with this, just move perpendicular to where the beam will be (preferably towards the middle), and immediately focus on the next incoming blaster. If you are still having trouble, try to focus on moving in one axis at a time. If the blaster is more horizontally aligned, only move up or down. If the blaster is more vertically or diagonally aligned, focus on the left and right. Sound cues are huge, and if you have sound on you can start focusing on the next blaster immediately after you hear the "BZZZRRWWWWW."

Attack 3 - Advanced DR
This is the same as the first DR attack, but with different possible sub-attacks.
More possible A-DR Attacks:

• Mini Conveyor - Like the first conveyor attack (in the first half), but you start on the side. Move diagonally, holding jump and tapping the arrow key right and you should be fine.
  
• X-Blaster - This attack is kind of similar to the first attack's ending sub-attacks. If you are struggling pick 2 special arrow keys that call out to you and if this attack comes, hold those two (for me, it's always left, and down if diagonal).
  
• Swing - Also, just like the portion of the first attack where a large amount of bones comes and you have to move vertically up and down.
  
• Two Platforms - There are two platforms in midair. Fall off the first one onto the second one and immediately jump back up, in a circular motion.

Attack 4 - Small Slammy
This is also one of the variants of the attack people have trouble with. It's mostly just you have to have a fast reaction speed in order to jump the direction you should go. If you are having trouble with reacting fast enough, try to look at Sans's hands instead of the red box. His hands move the direction gravity switches to slightly before the box shows up, so you have more time to react.

Attack 5 - Medium Slammy
Another one

Attack 6 - Large Blasters
The slightly harder variant of the small attack. If you got the first one down, then you should be able to adapt to this one pretty easily.

Attack 7 - Train Station
This one can also take some practice. There are 2 ways I like to do this attack. The first way is what you'd think: just moving in a square / circle. It's not that complicated, just press right, up, left, down repeatedly. However, another way of completing this is to move diagonally up and to the right, then down and to the left. It's not that big of a difference, but I always did it the second way for some reason, and it looks strange because the movement is pointy.That's the best I can explain. Just don't worry about it.

Attack 8 - Advanced DR pt. 2
A Dimensional Rift attack that combines all of the previous DR attacks into one, and slightly faster / harder. If your reaction time is up to par, you shouldn't have any problems.

Attack 9 - Large Slammy
This is the hardest slammy, and for me, it's more difficult than the special attack slammies, because of how long it is compared to the special attack. It's really easy to hit the right direction a fraction of a second too late, and if you do, subsequent slammies in the same direction will be harder to make. Practice makes perfect, so keep on keeping on with this attack.

Good Luck.

If you haven't practiced this attack before, you're kinda screwed. It will always be the same, so practicing and knowing the attacks before they come will help, especially for memorizing the slammy at the end of the attack.

The final attack (before the special attack) is the hardest attack, not only due to it being a combination of the other hardest attacks, but also due to the insane pressure of succeeding.

The first subsection of the final attack is a train station. Then comes a couple slammies. You know how to deal with these at this point.

Next, your heart is slammed against the wall and starts to move sideways towards the right. A simple up and down dodging movement will do the trick. The section all the way until you hit the far right wall should be simple.

Then comes a slammy, except these are a combination of two directions. The movement pattern (for the 2 directional ones after you get teleported from the long room) should be as follows: up, down+right, up+left, and right.

For the last slammy, instead of moving right, you also want to move down, because the dreaded pinwheel attack is about to come, and you want to prepare as adequately as possible.

The Pinwheel

BREATHE AS LOUDLY AS POSSIBLE AND MASH ALL 4 ARROW KEYS AT ONCE, PRAYING YOU DON'T CLIP ANYTHING.

But seriously, practice the pinwheel if you get far into a run, even if you are low hp. I practice this if I get into the second half at all. It hurts to lose within 5 seconds of winning.

After the pinwheel comes an unavoidable slam sequence which should bring you down to no less than 56 hp. This is unavoidable and cannot kill you, so it doesn't count as being hits.

CONGRATULATIONS!

Time to celebrate!

You've just no hit Sans. Now go do whatever it is that you do, and ponder your life choices tonight.

~Guide by S. Gates

~It took a lot longer to come up with the names of the attacks than to come up with useful tips. If you want more tips you better be sure to leave a positive review, buddy.

• The web browser version isn't very accurate and the physics are off, so using that to practice is a bad idea.
  
• Even if you fail a run, keep going to learn what's ahead.
  
• If you need to practice a section repeatedly, just check Sans and it won't progress the story.
  
• Exiting the game and then starting it is a lot faster than dying on purpose.
  
• Practice makes perfect, don't give up.