Uploaded February 2023 | Updated September 2026, 1 week ago
A messy little demonstration of something I just found. Basically lets you place two blocks in the same tick but at different positions, without any sort of lag.
Minecraft TAS people(me included) often say "you can only place one block per tick." But this isn't quite true. In fact, there is no hard limit on the number of times you can place a block in a tick! If you press “place block” 5 times in a tick, it will actually try to place 5 blocks. The issue is that your target position(aka the coords of the block you're looking at) only updates once per tick. And since each block you try to place uses this same position to calculate where it should be placed, this usually means all 5 of your blocks will try placing in the same exact spot. This is actually fine for some blocks like snow layers or scaffolding, since they let you place multiple in the same position by design(try placing 64 scaffolding in a tick, its fun!!). But, for other blocks like stone or smthn, trying to place 5 in one position will only let one successfully place, while the rest get canceled.
So, if that's the case, then what's happening in this video?
While it is true that every block you try to place will use the same target position, this isn't the only factor involved in deciding where the block get placed. Under most circumstances, the position it chooses is just adjacent to the target position, offset based on the face of the hitbox you were looking at that tick. However, if the block at the target position is deemed "replaceable," then the block gets placed right at the target position instead(think placing a block on tall grass). This gives us two possibilities for where a block can be placed for a given tick: adjacently to the target position, or directly on the target position. So if you place two blocks in a tick, and one chooses the adjacent position, and the other chooses the replaced position, then they'll both successfully place. This is what I'm calling a "double place," since it places blocks at two different positions in a single tick.
But now the question is, what makes a block replaceable? And how can we actually use this?
Well, if the block at your target position is one of these then it's always replaceable, unless you're trying to place that same block:
Structure Void
Grass
Fern
Dead Bush
Tall Grass
Large Fern
Warped Roots
Nether Sprouts
Crimson Roots
Seagrass/Tall Seagrass
Fire/Soul Fire
Air
Water
Bubble Column
Lava
Or if the block at your target position is one of these, then it's a bit more specific:
Scaffolding - Replaceable if you're placing scaffolding
Sea Pickle - Replaceable if it has less than 4 pickles and you're placing a pickle
Turtle Egg - Replaceable if it has less than 4 eggs and you're placing an egg
Slabs - Replaceable if you're placing its other half
Snow Layer - If it's 1 layer, always replaceable unless placing another snow layer. If there's more than 1 layer, then it's only replaceable if you're placing a snow layer on the top. At 8 layers it's never replaceable.
Vines - Always replaceable, unless the block is fully vined(all 5 sides)- even if there's less than 5 blocks for it to cling to or if you're placing a vine. It's actually impossible to place a vine adjacent to another vine.
That's a lot of info, but its nothing scary. Just satisfy one of these conditions for one block you place, and then don't satisfy any for another. Consider the "Standard Replaceable Blocks" examples in the video:
The first block I try to place sees that the block at my target position is grass/snow/fire(replaceable!), so it places directly at my targeted position. But then the second block sees that the block at the target position is now cobblestone(not replaceable!) so it places adjacently instead. This successfully places the two blocks in a single tick.
But what about the "Replaceable Blocks via Insta-mine" examples? TNT/slime definitely aren't replaceable, but air sure is! If you insta-mine a block and place two blocks in the same tick, first the insta-mine turns the block at your selected position to air. So when your first block tries to place, it sees air at the target position(replaceable!), so it places directly at the targeted position. Then the next block sees that the block at the target position is now cobblestone(not replaceable!) so it places adjacently. You can even do this underwater, since water is replaceable too.
The "Stacked Replaceable Blocks" section just shows that this isn't exclusive to placing 2 blocks. For the 1st one, the first 10 blocks are placing scaffolding on scaffolding(replaceable!), so it does its thing. But the 11th is placing cobblestone on scaffolding(not replaceable!) so places adjacently.
Not sure when it was added, but I managed to do it in vanilla 1.8-1.19. I actually think this is what happens in my HDWGH TAS(youtu.be/6FrDXg3W8uM) at 1:00 when I place 2 sandstone. I always chalked it up to lag, but I could have just placed them on the side of the grass block.
A messy little demonstration of something I just found. Basically lets you place two blocks in the same tick but at different positions, without any sort of lag.
Minecraft TAS people(me included) often say "you can only place one block per tick." But this isn't quite true. In fact, there is no hard limit on the number of times you can place a block in a tick! If you press “place block” 5 times in a tick, it will actually try to place 5 blocks. The issue is that your target position(aka the coords of the block you're looking at) only updates once per tick. And since each block you try to place uses this same position to calculate where it should be placed, this usually means all 5 of your blocks will try placing in the same exact spot. This is actually fine for some blocks like snow layers or scaffolding, since they let you place multiple in the same position by design(try placing 64 scaffolding in a tick, its fun!!). But, for other blocks like stone or smthn, trying to place 5 in one position will only let one successfully place, while the rest get canceled.
So, if that's the case, then what's happening in this video?
While it is true that every block you try to place will use the same target position, this isn't the only factor involved in deciding where the block get placed. Under most circumstances, the position it chooses is just adjacent to the target position, offset based on the face of the hitbox you were looking at that tick. However, if the block at the target position is deemed "replaceable," then the block gets placed right at the target position instead(think placing a block on tall grass). This gives us two possibilities for where a block can be placed for a given tick: adjacently to the target position, or directly on the target position. So if you place two blocks in a tick, and one chooses the adjacent position, and the other chooses the replaced position, then they'll both successfully place. This is what I'm calling a "double place," since it places blocks at two different positions in a single tick.
But now the question is, what makes a block replaceable? And how can we actually use this?
Well, if the block at your target position is one of these then it's always replaceable, unless you're trying to place that same block:
Structure Void
Grass
Fern
Dead Bush
Tall Grass
Large Fern
Warped Roots
Nether Sprouts
Crimson Roots
Seagrass/Tall Seagrass
Fire/Soul Fire
Air
Water
Bubble Column
Lava
Or if the block at your target position is one of these, then it's a bit more specific:
Scaffolding - Replaceable if you're placing scaffolding
Sea Pickle - Replaceable if it has less than 4 pickles and you're placing a pickle
Turtle Egg - Replaceable if it has less than 4 eggs and you're placing an egg
Slabs - Replaceable if you're placing its other half
Snow Layer - If it's 1 layer, always replaceable unless placing another snow layer. If there's more than 1 layer, then it's only replaceable if you're placing a snow layer on the top. At 8 layers it's never replaceable.
Vines - Always replaceable, unless the block is fully vined(all 5 sides)- even if there's less than 5 blocks for it to cling to or if you're placing a vine. It's actually impossible to place a vine adjacent to another vine.
That's a lot of info, but its nothing scary. Just satisfy one of these conditions for one block you place, and then don't satisfy any for another. Consider the "Standard Replaceable Blocks" examples in the video:
The first block I try to place sees that the block at my target position is grass/snow/fire(replaceable!), so it places directly at my targeted position. But then the second block sees that the block at the target position is now cobblestone(not replaceable!) so it places adjacently instead. This successfully places the two blocks in a single tick.
But what about the "Replaceable Blocks via Insta-mine" examples? TNT/slime definitely aren't replaceable, but air sure is! If you insta-mine a block and place two blocks in the same tick, first the insta-mine turns the block at your selected position to air. So when your first block tries to place, it sees air at the target position(replaceable!), so it places directly at the targeted position. Then the next block sees that the block at the target position is now cobblestone(not replaceable!) so it places adjacently. You can even do this underwater, since water is replaceable too.
The "Stacked Replaceable Blocks" section just shows that this isn't exclusive to placing 2 blocks. For the 1st one, the first 10 blocks are placing scaffolding on scaffolding(replaceable!), so it does its thing. But the 11th is placing cobblestone on scaffolding(not replaceable!) so places adjacently.
Not sure when it was added, but I managed to do it in vanilla 1.8-1.19. I actually think this is what happens in my HDWGH TAS(youtu.be/6FrDXg3W8uM) at 1:00 when I place 2 sandstone. I always chalked it up to lag, but I could have just placed them on the side of the grass block.
