All 122 Fallout Vaults Explained: Every Vault-Tec Experiment

Vault-Tec sold the Vaults as humanity’s insurance policy. Three feet of lead, a fusion reactor, food for generations, and a door that would open once the surface was safe again. The advertising was relentless and, for a country watching the Resource Wars burn through Europe, it worked. People took out second mortgages for a spot.

Only 17 of the 122 Vaults were built to do what the brochure said.

The count, up front: there are 122 Vaults in Fallout — 17 controls, 105 experiments, and only 47 of them ever named or described. Where each of those four numbers comes from is the next section.

What Vault-Tec sold: a door in a mountainside, a family in line, a mushroom cloud on the horizon. The promise was that the door would open again.

The other 105 were experiments. Not metaphorically — each one had a written protocol, a hypothesis, and a data-collection plan filed with a corporation that had no intention of ever telling the residents. This is the complete guide to what those protocols were: which Vault ran which experiment, where the number 122 actually comes from, what the surviving records say happened, and — the part almost every retelling gets wrong — what the whole program was ultimately meant to produce.

The other side of the same door, two hundred years on. Most of the 105 protocols ended somewhere close to this.

Where the numbers come from

Three figures get quoted constantly. Two are solid, one is routinely misattributed.

122 Vaults. Project Safehouse was authorized in 2054, in the aftermath of the Euro-Middle Eastern War, the New Plague, and the collapse of the United Nations. A government already deep in debt financed it with junk bonds, and even then commissioned only 122 shelters — enough for well under 0.1% of the American population. For where the Vault program sits on the pre-war timeline, see the complete Fallout timeline. The cost per unit was ruinous: Vault 13 was budgeted at $400 billion and finished at $645 billion, more than 150% of the original figure.

17 control Vaults. This number is not from a developer interview or a supplementary document, as it is often claimed. It is stated in-game, on a Vault-Tec terminal recovered by the Brotherhood of Steel and readable inside the Citadel in Fallout 3. The entry describes Vault 76 as one of seventeen control Vaults — shelters built to run exactly as advertised, so that the experimental Vaults would have a baseline to be measured against. That makes it a primary source, and it is the reason the 105/17 split can be stated as fact rather than fan arithmetic.

105 experiments. Simple subtraction, and the weakest of the three in practice — because only a fraction of those 105 were ever documented. More on that below.

Why the experiments existed

The standard answer, repeated across a decade of videos and articles, is that the Enclave wanted psychological data on how to control a post-war population. That is not what the experiments were designed for, and the person who designed them has said so directly.

Tim Cain, co-creator of the original Fallout, explained the origin in a 2023 video on his personal channel. The idea started as a math problem raised by designer Chris Taylor: even a thousand Vaults the size of Vault 13 would hold a million people, against a US population in the hundreds of millions. As a plan to preserve the nation, the Vault program is absurd on its face. So it could not have been the plan.

What made sense instead was that the shelters were prototypes. The people who became the Enclave assumed the surface would be permanently uninhabitable, and concluded that the future of the species was a multi-generational starship — a sealed environment carrying a small population for centuries. Nobody had ever built one. Nobody knew whether a closed society of a thousand people survives two hundred years, what breaks first, how much isolation a crew tolerates, whether cryogenics works on people, whether a single unchallenged authority holds a population together or tears it apart.

The Vaults were the test rig. Every experiment that looks gratuitously cruel is a variable being isolated: what happens if we remove entertainment, break the clothing supply, unbalance the sexes, hand them unlimited weapons, freeze them, put one man alone with a crate of puppets. The Vault-Tec director proposed it; the government funded it; the residents were never told.

One caveat that matters, and that we will not paper over: Cain also said he has no idea whether Bethesda still holds to the starship rationale, and that they may have discarded it entirely. I have found nothing in Fallout 3, 4, 76, or the TV series that states it. So treat it as the original design intent — authoritative for the first two games, plausible and unconfirmed for everything after.

The 17 control Vaults

A control Vault is simply one with no protocol attached: three feet of lead, a fusion reactor, generations of food, and a door on a timer — built to do exactly what the brochure said. They were not the lucky Vaults. They were a required part of the design: without a set of sealed societies running on normal parameters, nothing that happened in the other 105 could be attributed to any variable at all.

Four of the seventeen have been identified. They are the least interesting Vaults to visit and the most important to understand, because without them the other 105 produce no usable data.

Note the pattern: two of the four were destroyed anyway, and a third was compromised by its own operators. A control group only stays a control group if nothing touches it, and something touched almost all of them. Of the four, only Vault 76 opened on schedule.

The brochure cutaway: clinic, diner, dormitories, power plant. All of it was really built. None of it was the point.

The experiment Vaults

Below is every numbered Vault with a documented experiment. They are grouped by what was being tested, because the protocols cluster far more tightly than the “wacky Vault-Tec” framing suggests — and once you see the clusters, the starship rationale becomes hard to unsee.

Isolation and social structure

Class, scarcity, and deprivation

Sex ratio and reproduction

Chemical, biological, and radiological

Vault 33 in the television series — the only one of the three linked Vaults still running, its residents still unaware of where their Overseers come from.

Authority, identity, and machine control

Neither shelter nor experiment

Three Vaults were built by Vault-Tec but were never part of the social-experiment program at all, which is worth knowing before you assume every Vault number implies a protocol.

The 75 Vaults nobody has ever described

Add it up: 37 numbered Vaults appear in canonical material, and another 10 exist only in supplementary documents. That is 47 out of 122 — and several of those 47 amount to a single sentence with no recorded outcome.

Seventy-five Vaults have never been named, placed, or described in any form.

This is not an oversight to be filled in by speculation, and it is the reason to be skeptical of any list claiming to cover “all 122.” The heat map shown in the first-season finale of the TV series is the closest thing to a complete picture: roughly 116 dots spread across nearly every contiguous state, designed not by the show’s art department but by Bethesda Game Studios at production designer Howard Cummings’ request. Clusters sit where you would expect — around Washington DC, around Appalachia, a triangle of three in Los Angeles for Vaults 31, 32 and 33. Four sit over Houston. Two are in Oklahoma and one in central Canada, matching a Vault-Tec letter in Fallout 3 that advertises accommodation in “exciting locales such as Oklahoma and newly-annexed Canada.”

The map does not line up one-to-one with the games, and it is dated to 2074 in the script — three years before the war, with construction still underway. Treat it as intent, not inventory.

How to read the sources

Fallout lore is stratified, and conflating the layers is where most Vault articles go wrong. Four tiers, in descending order of authority:

• In-game text. Terminals, holotapes, dialogue. The 17 control Vaults, Vault 108’s four-part protocol, Vault 11’s fabricated threat — all of this is readable in the games themselves. Highest confidence.
• The TV series. Bethesda-supervised and treated as canon; Vaults 4, 24, 31, 32 and 33 exist nowhere else. Newer than most of the games, and it has introduced at least one point of open contradiction with them.
• The Fallout Bible. Chris Avellone’s supplementary documents, 2002. Vaults 27, 36, 42, 53, 55, 56, 68, 69 and 70 come from here and nowhere else. Avellone himself said in 2011 that it should not be treated as canon, and in 2022 narrowed that further. Bethesda has never issued a ruling either way — Emil Pagliarulo’s position in 2020 was that canon starts with what is in the games, and beyond that it is a judgement call. So these nine are real, widely repeated, and formally unconfirmed.
• Everything else. Fallout Tactics’ Vault 0, the Brotherhood of Steel vaults, the Van Buren design documents, fan projects such as Fallout: New California, and the board game. Interesting, not canon, and the most common source of numbers that turn up in listicles without qualification.

Every Vault in the tables above is labelled with its tier. Where a claim rests on a single source, we have said so rather than smoothing it over.

Frequently asked

How many Vaults are there in Fallout? 122 were commissioned — 17 controls and 105 experiments. Several — Vault 88 and Vault 114 among them — were still unfinished when the bombs fell on 23 October 2077, so the number completed is lower and has never been stated.

Which Vault is the worst? By body count, Vault 87: the entire civilian population was converted into super mutants. By duration of suffering, Vault 112, where Braun tortured his residents inside a simulation for over two hundred years and could restart it at will.

Did any Vault simply work? Yes. Vault 8 opened on schedule and built Vault City. Vault 76 opened on schedule and reclaimed Appalachia. Vault 21 ran an absurd protocol and still produced a stable society for two centuries. Vault 81’s civilian half is alive and functioning in 2287 — and has never been told what was happening on the other side of the wall.

Were the residents ever told? Almost never. Vault 4 is the notable exception: its status as an experiment was publicly acknowledged. In Vault 81 and Vault 101, the Overseer knew and the population did not. In Vault 111, the residents were told the cryogenic pods were decontamination chambers.

Who was collecting the data? All Vaults reported to what became the Enclave — for where the Enclave itself came from, and how it relates to the Brotherhood and the Institute, see the guide to Fallout’s factions. Outside it, knowledge was restricted to a minority of Vault-Tec staff — mostly Overseers — and senior figures in the military-industrial complex.

Sources

In-game text and data. In-game terminal entries and dialogue from Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout 4 and Fallout 76; the Vault-Tec Corporation entry and the individual vault entries (Vault 13, Vault 15, Vault 8, Vault 12, Vault 87, Vault 111, Vault 81, Vault 76 and others).

Television and official publications. The Fallout television series and its published scripts; One Man, and a Crate of Puppets.

Developer material. The Fallout Bible (Chris Avellone, 2002); Tim Cain’s 2023 video on the origin of the Vault experiment (his YouTube channel CainOnGames).

Where sources disagree, both positions are stated above.