Every UUID: the website that lists all 5.3 undecillion UUIDs

At first glance Every UUID looks like the world's most pointless spreadsheet: one endless column of universally unique identifiers, all 5.3 undecillion of them, that a visitor can scroll through and search. It is worth a look because the premise is deadpan nonsense, the execution is genuinely clever, and the whole site is a hard engineering problem solved in the service of a joke.

In brief

• Every UUID presents all possible version-4 UUIDs, about 5.3 undecillion of them, as one scrollable and searchable page at everyuuid.com.
• Nothing is stored anywhere: each UUID is calculated on the fly from its position in the list, so the entire database is really a short piece of maths.
• The order looks random but never changes, because a reversible cipher maps each row number to exactly one UUID and back again.
• It was built by Nolen Royalty, the developer behind the viral One Million Checkboxes, who published a detailed account of the tricks involved.

What Every UUID actually is

Open everyuuid.com and the page shows a plain vertical column of UUIDs, one per row, with a search box at the top and a scrollbar down the side. It looks like the most boring spreadsheet ever exported. The joke sits in the title, Every UUID V4, and in the claim beneath it: this is not a sample but all of them, every version-4 UUID that could ever be produced, gathered in one place and waiting to be looked up.

A UUID, or universally unique identifier, is the long run of hexadecimal digits and dashes that software scatters everywhere to label things without collisions, described in full on Wikipedia. Version 4, the most common kind, is almost entirely random. The whole point of a UUID is that a program mints one and never thinks about it again. Every UUID takes that disposable, forgettable object and does the exact opposite, collecting every last one into a single browsable page.

The maker plays it completely straight. The project's GitHub repository describes the site as a searchable list of every UUID, kept in case you have forgotten one and need to look it up. That is the entire pitch, delivered without a wink, and the page commits to the bit from top to bottom.

The number that makes it absurd

Scale is where the premise stops being cute and turns genuinely strange. In his write-up of the build, Nolen Royalty explains that although a UUID carries 128 bits, version 4 reserves four bits for the version and two for the variant he picked, which leaves 122 bits of real randomness.

Two to the power of 122 is a number most people never have reason to write out. Royalty gives it in full: 5,316,911,983,139,663,491,615,228,241,121,378,304 possible UUIDs. That is roughly 5.3 undecillion, a 5 trailed by thirty-six digits.

A figure that size resists intuition, so a comparison helps. If every person alive generated a million UUIDs every second, the whole list would still take many times the present age of the universe to finish. Every UUID's plain little scrollbar is a handle on a quantity that does not fit inside a human head, and that mismatch is the source of most of its charm.

The trick: nothing is actually stored

The obvious way to build the site would be to generate the list and save it, which is flatly impossible. Those 5.3 undecillion strings would not fit on every hard drive ever manufactured, never mind inside a browser tab. So nothing is stored at all. As Royalty describes, each UUID is computed from its position the instant it needs to appear, then discarded as it scrolls out of view.

The hard part is making that live computation behave like a fixed list. If row one thousand showed a different value on every visit, the site would be pointless. Royalty needed a mapping from a row number to a UUID that never changes, never repeats, and looks convincingly shuffled rather than counting neatly upward.

His answer is a Feistel cipher, a classic cryptographic construction that scrambles a number reversibly. It splits the 122-bit position into two halves and stirs them through several rounds of arithmetic. Because every step can be undone, the mapping is a perfect one-to-one shuffle: each row leads to exactly one UUID, and each UUID back to exactly one row. As he puts it, as long as he could always reverse the steps he took, he had preserved bijectivity.

That one design choice is what lets the page act like a real, permanent list while holding nothing in memory. The order looks random, stays identical between visits, and covers all 5.3 undecillion values without ever skipping or duplicating a single one.

Scrolling through a number too big to scroll

Showing the list raises a second, separate problem, and it is a pleasingly backwards one: a browser cannot scroll that far. Royalty found that browsers cap how tall a page may be and how far it can be scrolled, with some holding the scroll position in a 32-bit integer. Even if each UUID were crushed down to a single pixel of height, the page would need to stand many orders of magnitude taller than any browser permits.

So he abandons real scrolling altogether. The page height is pinned to the size of the browser window, and a virtual scroll position is tracked separately in a BigInt, a JavaScript type made for whole numbers too large for ordinary variables. Spinning the wheel, pressing the arrow keys, and dragging the scrollbar all simply push that hidden number up or down.

Wherever the virtual position settles, the site renders only the handful of UUIDs that belong on screen at that moment, each worked out fresh from its row number. The visitor sees a smooth, unremarkable scroll. Underneath there is no tall page at all, only a tiny moving window onto a number line 5.3 undecillion entries long. Royalty notes he had to rebuild the keyboard handling, the scrollbar, and the animation that a browser normally supplies for nothing.

How the search finds one in the pile

A list nobody can meaningfully scroll clearly needs a search box, and this is where the reversible cipher earns its place. Type a complete UUID and the site runs the Feistel shuffle backwards to recover the row number that produces it, then jumps straight there. The value never has to be found by looking, because its position can simply be calculated.

Fragments are harder and more ingenious. Royalty explains that when a visitor types part of a UUID, the site reasons about where that fragment could legally sit inside a valid version-4 identifier, respecting the fixed dashes, the mandatory 4, and the restricted variant digit. It then builds candidate UUIDs that contain the fragment and, as Simon Willison summarised it when the site launched, picks the one closest to your current position on the page.

Royalty is honest that this half is not perfect, because fully reversing a fragment search proved intractable once every input bit affects every output bit. In normal use it still feels like sleight of hand: type a few characters that mean something to you and the page glides to a real UUID wearing them.

Who made it, and the checkboxes before it

Every UUID is the work of Nolen Royalty, a developer who writes up his projects at eieio.games. It arrived in the wake of a bigger hit. Earlier in 2024 he built One Million Checkboxes, a shared page of a million boxes that anyone could tick, with every change visible to everyone at once. It went viral, pulled a large crowd, and earned its own Wikipedia article.

The two projects share a temperament. Both seize a dull technical primitive, a checkbox, a UUID, and inflate it to an absurd scale until the sheer quantity becomes the entertainment. Both also tuck real engineering under a silly surface, which is much of why other developers enjoy taking them apart.

That crowd found the site fast. Every UUID reached the top of Hacker News on 6 December 2024, drawing more than 1,400 points and a long, technical comment thread. Simon Willison wrote it up the next day, Andy Baio covered it at Waxy, and it has kept resurfacing in the months since.

Why a useless page is worth a minute

On paper Every UUID does nothing. There is no game, no account, no goal, and nothing to save. It belongs to the same small network of single-purpose sites as Today's Rock, pages built on the plain idea that a website can be one self-contained joke or pleasure and has no duty to be anything more.

What makes this one linger is the gap between the flat, boring surface and the strange thing it stands for. Scrolling the list is a way of holding, for a moment, a quantity so vast it is effectively every UUID that ever has been or ever will be handed out by anyone. Somewhere in that scroll is the identifier a database invented for a forgotten order last Tuesday, and the one it will invent next year.

It also rewards a particular kind of visitor. Anyone who has lost an afternoon to an endless-scroll toy such as Xikipedia will know the pull of a page that just keeps going. Every UUID adds a quiet twist: the thing it never stops producing is, technically, complete and finite. A visitor could in principle reach the end. They simply never will.

How to get the most out of it

The site is more fun with a target than without one. Paste in a UUID from a log file or a database row and watch the page leap to its exact spot, proof that the identifier really does live somewhere in the list. Failing that, search for a word that fits the hexadecimal alphabet, such as face, cafe, dead, or beef, and the site will surface a real UUID wearing it.

Beyond that, the reward is in reading the write-up beside the toy. Royalty's account of the build turns a two-minute curiosity into a small lesson in how to fake infinity inside a browser. The page is the punchline, and the blog post is the working that sits behind it.

FAQ

Does Every UUID really contain every possible UUID?

It contains every version-4 UUID, the common random kind. According to its maker's write-up, that is two to the power of 122 values, about 5.3 undecillion, none of them stored in advance. Each one is calculated from its position the instant it appears on screen.

Are the UUIDs in a fixed order?

Yes. The order looks random but never changes, because a reversible Feistel cipher maps each row number to one specific UUID. The same row always shows the same UUID, which is what makes both searching and sharing a position possible.

How can you search a list that huge?

For a full UUID, the site runs its shuffle backwards to find the matching row and jumps there. For a fragment, it works out where the fragment can sit inside a valid UUID and builds a matching one near your current spot, an approach Simon Willison described when the site launched.

Who made Every UUID?

Nolen Royalty, the developer behind the viral One Million Checkboxes. He released Every UUID in December 2024, where it reached the top of Hacker News, and documented the engineering on his blog at eieio.games.