RNG Algorithms: The Secret Behind Gacha Systems That Keep You Hooked

If you have ever played a gacha game — grinding for that SSR or chasing a limited-time character — you have probably wondered: is this actually random, or is something rigged behind the scenes? The answer lies in one technical term: RNG, or Random Number Generator.

What Is RNG?

RNG is an algorithm that produces a sequence of numbers that appear random. Computers cannot actually generate truly one hundred percent random numbers — which is why what gets used is a Pseudo-Random Number Generator (PRNG): an algorithm that produces a sequence of numbers that looks random but is actually calculated from a starting value called a seed. In many gacha games, that seed can come from the player User ID or the server time.

Because the result is computed from a mathematical formula, the same seed and algorithm will always produce the same "random" outcome. That is why it is called pseudo-random — it looks random, but it is actually deterministic.

How Do Games Decide Drop Rates?

What makes an RNG outcome feel fair or unfair is not really the RNG algorithm itself, but the probability table the developer has set up. For example, a Legendary item might be set at a 1% drop rate, while a Common item sits at 70%. Every time you pull, the system generates a random number and matches it against that probability table to determine what you get.

Meet the Pity System

This is what sets modern gacha apart from pure gambling — the pity system. It boosts your odds of landing a rare item the more times you fail in a row. According to dotgg.gg (2026), one of the games that popularized this system was Granblue Fantasy, which introduced "hard pity" back in 2016 — players were guaranteed their target item after a set number of pulls (300, in that case) at no extra cost.

There are two common types of pity:

• Hard pity — a fixed ceiling: once you hit it, your target item is guaranteed.
• Soft pity — your odds climb gradually the more you miss, before eventually reaching hard pity.

So, Is It Actually Random?

Technically, each pull is indeed computed through a random process (PRNG). But the system as a whole — drop rates, pity, even the odds of a "rate up" — is all governed by carefully designed probability, not left to chance. So RNG in gacha games is random in execution, but tightly controlled by design — a mix of math and psychology engineered to keep the game exciting without pushing players into total frustration.