The Index is the collection log in Steal a Brainrot - and one of the few permanent income upgrades you earn purely by owning brainrots rather than by grinding cash. Fill enough of it and every brainrot you ever place earns more, forever. This guide covers how the stacks work, what the multiplier is actually worth, and the fastest ways to close the gaps.
Read this first: the Index thresholds below are percentages, not fixed counts, and the pool of indexable brainrots grows with every update - so the number of brainrots you need moves too. Figures are as of September 2026, cross-checked between the Steal a Brainrot wiki Index page and u7buy's Index system guide. Trust the counter inside your own Index menu over any guide, ours included.
What the Index actually is
Open the Index in-game and you get a grid of every brainrot in Steal a Brainrot - minus a handful the wiki flags as non-indexable - with the ones you have already owned filled in. A brainrot registers the first time it reaches your base, and the entry is permanent: sell it, trade it away, or lose it to a stealer, and it stays filled in. Both u7buy's mechanics guide and ssegold's indexing guide describe it the same way.
That single detail is what makes the Index worth planning around. Every brainrot that passes through your base is progress, no matter how briefly you held it.
The four permanent Index stacks
Each mutation keeps its own separate Index. The four permanent ones are Normal (no mutation), Gold, Diamond and Rainbow - and they do not share progress. To fill the Gold Index you need the Gold version of each brainrot; your Normal copy does not count towards it.
| Index | Completion requirement | Reward |
|---|---|---|
| Normal (Default) | 75% of indexable brainrots | +0.5x base multiplier |
| Gold | 75% of indexable brainrots | +0.5x base multiplier + Gold base skin |
| Diamond | 75% of indexable brainrots | +0.5x base multiplier + Diamond base skin |
| Rainbow | 75% of indexable brainrots | +0.5x base multiplier + Rainbow base skin |
The wiki and u7buy give the same 75% threshold and the same +0.5x reward for all four. We deliberately do not print a fixed "you need N brainrots" figure - the indexable pool grows with every update, so any hard count is stale within weeks. Read the live percentage in your own Index instead. For the same reason, an Index you completed months ago can quietly drop back under the line when a big update ships, so re-check it after every major patch.
What the multiplier is actually worth
Completing all four permanent Indexes leaves you with a permanent +2.0x base multiplier (four stacks at +0.5x each) applied to every brainrot you place, stacking on top of your rebirth multiplier and any traits. It is not a one-off payout or a timed boost - it is a floor raise on your entire base for the life of the account.
In practice that is the gap between a mid-game and a late-game base without changing a single brainrot. Index progress and rebirth progress also pull in the same direction: see the rebirth guide for the cash and brainrot requirement at each step, and the income calculator for what your current setup earns per second.
The limited-time mutation Indexes
Seasonal and event mutations get their own Index too. These award the matching base skin and are locked to brainrots that existed before a cutoff date, so they never grow - which also means a missed window is missed for good. The wiki and u7buy agree on these:
| Index | Requirement |
|---|---|
| Candy | 100% of brainrots added before 25 July 2025 |
| Lava | 100% of brainrots added before 23 August 2025 |
| Radioactive | 75% of brainrots added before 3 January 2026 |
| Cursed | 60% of brainrots added before 21 February 2026 |
| Divine | 60% of brainrots added before 18 April 2026 |
| Cyber | 60% of brainrots added before 13 June 2026 |
Note the lower bar on the newer ones - 60% of a frozen, older roster is a far more realistic target than 75% of a growing one, which is why the recent event Indexes are usually the most achievable base skins to chase.
Mutations and the Index
Because every mutation keeps its own Index, a mutated brainrot is doing two jobs at once: earning more right now, and filling a second collection log. Hunting Gold or Diamond copies of brainrots you already own in Normal is therefore never wasted effort - which is not obvious the first time you open the menu.
Mutation multipliers get patched, so pull the current numbers from our Steal a Brainrot mutations page rather than memorising a list.
Fastest ways to fill the gaps
- •Work out what you are actually missing. Your own Index menu is the only reliable list - third-party rosters go stale within days of an update.
- •Trade for the cheap gaps first. Most holes are low-tier brainrots nobody hoards, and player trading clears them fastest. Run any offer through the trade calculator before you accept, and read our Roblox trading safety guide if you are trading with strangers.
- •Price the expensive gaps before you grind for them. Check the Steal a Brainrot value list to see which missing entries are genuinely rare - several are unobtainable in-game now and can only be traded or bought. Our rarest brainrots guide covers which ones those are and why.
- •Buy the ones that will never spawn for you. Event and Fuse Machine exclusives are gone for good. If one of them is the last entry between you and a +0.5x stack, grabbing it from the BloxUltra Steal a Brainrot shop with ~10-minute delivery beats any amount of luck - and because the entry is permanent, it only has to touch your base once.
Steal a Brainrot Index FAQ
How do you complete the Index in Steal a Brainrot?
For any of the four permanent Indexes - Normal, Gold, Diamond and Rainbow - you need 75% of the game's indexable brainrots registered in that Index. Seasonal event Indexes use their own thresholds. A brainrot registers the first time it reaches your base, so you can sell or trade it afterwards and keep the entry. Completing a permanent Index (Normal, Gold, Diamond or Rainbow) grants a permanent +0.5x base multiplier, and the mutation Indexes also unlock a matching base skin. Thresholds per the Steal a Brainrot wiki and u7buy, September 2026.
How much multiplier does the Index give?
Each completed Index adds +0.5x to your base multiplier permanently. Completing all four permanent Indexes - Normal, Gold, Diamond and Rainbow - stacks to +2.0x on every brainrot you place, on top of your rebirth multiplier and any traits.
Do you keep Index progress if you sell or lose a brainrot?
Yes. The Index records that you have owned a brainrot, not that you currently own it, so selling it, trading it away or having it stolen does not remove the entry. That is why trading for cheap missing brainrots is such an efficient way to close gaps.
Sources: Steal a Brainrot Wiki - Index, u7buy - Steal a Brainrot Index system guide, ssegold - Steal a Brainrot indexing guide. Thresholds and rewards as of September 2026; the indexable pool changes with every update.