Locator Bar

Minecraft UUID: What It Is and How It Works

A Minecraft UUID is the 128-bit number that identifies a Java account for good. What the format means, online vs offline UUIDs, and why the Locator Bar reads it.

最近更新: 2026-07-23

Every Java Edition account carries a number that never changes: its UUID. Your username can change every 30 days, your skin can change hourly, but the UUID minted when the account was registered stays with it for the life of the account. Servers store bans against it, plugins store balances against it, and since the 1.21.6 drop the Locator Bar reads it to decide what color your marker is on everyone else's HUD.

This page explains what that number actually is, how to read one by eye, and the one distinction that trips almost everybody up — the difference between an online-mode UUID and an offline-mode UUID.

If you only want your own number and your Locator Bar color, skip the theory and use the Minecraft UUID color finder — type a username, get the UUID and the exact marker color back.

What a UUID is

The Minecraft Wiki defines it plainly: a UUID is "a 128-bit long number that is used by Minecraft as a label to distinguish between separate instances." It is not a Minecraft invention. UUIDs are a general computing standard, currently specified by RFC 9562, and Minecraft just uses them the way thousands of other systems do — as a name that is guaranteed not to collide with anybody else's name, without needing a central authority to hand them out one at a time.

128 bits is a large space. Written out, it is roughly 3.4 × 10^38 possible values. That is why nobody worries about two accounts accidentally receiving the same one.

The formats you will actually see

The same 128 bits get written down four different ways depending on where you find them.

Hyphenated hexadecimal. The standard form, and the one commands and most websites expect:

069a79f4-44e9-4726-a5be-fca90e38aaf5

Thirty-two hex digits split 8-4-4-4-12 by hyphens. This is Notch's real UUID, and it is the example used throughout this site because it is easy to verify against any public lookup.

Trimmed hexadecimal. The same digits with the hyphens stripped. This is what Mojang's own API returns:

069a79f444e94726a5befca90e38aaf5

Neither form carries more information than the other. Re-inserting hyphens at positions 8, 12, 16 and 20 converts one to the other, and every decent tool accepts both.

Int-array. Since snapshot 20w12a (Java Edition 1.16), entity NBT stores UUIDs as four signed 32-bit integers, most significant first:

[I;-132296786,2112623056,-1486552928,-920753162]

If you run /data get entity @s UUID in game, this is the shape you get back. It looks nothing like the hyphenated form, but it is the same number.

Most/Least. The pre-1.16 storage format, splitting the value into UUIDMost and UUIDLeast long tags. Deprecated, but you will still meet it in old world saves, old datapacks and old forum posts.

Reading the version digit

Two of the digits in a UUID are not random. They are metadata, and the more useful one is the version, which sits at the first character of the third group:

xxxxxxxx-xxxx-Vxxx-Nxxx-xxxxxxxxxxxx
                ^
                version

For Notch's UUID, 069a79f4-44e9-4726-..., the third group is 4726, so the version is 4.

That matters because the Minecraft Wiki states the rule exactly: "Minecraft uses version 4, variant 1 (RFC) UUIDs, which means that the entire number with the exception of the bits used for metadata (version and variant) is randomly generated." Version 4 means randomly generated. Java's own UUID.randomUUID() produces exactly this, and the Oracle documentation describes it as "a type 4 (pseudo randomly generated) UUID."

So a real, paid, online-mode Java account always has a 4 there. If you are looking at a UUID whose third group starts with anything else, it did not come from Mojang's account system.

The N position holds the variant. For every Minecraft UUID it is one of 8, 9, a or b, which encodes the RFC 4122 / RFC 9562 layout. It is rarely worth thinking about, but it is a quick sanity check: a "UUID" with a c or f there is almost certainly hand-typed garbage.

Online mode versus offline mode

This is the part that causes the most confusion, and it is worth being precise about.

Online mode (online-mode=true in server.properties, the default) means the server verifies every joining player against Mojang's account database. The UUID it uses is the account's real, version 4 UUID — the same one Mojang's API returns, the same one on every other online-mode server in the world.

Offline mode (online-mode=false, informally "cracked") means the server does no verification at all. There is no account to look up, so there is no real UUID to use. The server has to invent one, and it does so deterministically from the username. The Minecraft Wiki spells out the recipe: offline players get "UUID version 3, generated from the MD5 hash of OfflinePlayer:<username>."

Three consequences follow, and all three bite people in practice:

  1. Offline UUIDs are version 3, not version 4. Hash the string OfflinePlayer:Notch with MD5, set the version and variant bits, and you get b50ad385-829d-3141-a216-7e7d7539ba7f. Look at the third group: 3141. That leading 3 is the tell. Any UUID whose third group starts with 3 came from an offline-mode server, not from Mojang.

  2. Offline UUIDs are derived from the name, so they follow the name. On an online server, renaming keeps your identity. On an offline server, renaming creates a completely new identity — new inventory, new permissions, new everything — because the name is the key.

  3. The two never match. The offline UUID for Notch (b50ad385-...) has nothing to do with the real account's 069a79f4-.... Switching a live server between online and offline mode without a UUID migration is the classic way to make every player's data disappear at once. The data is still there; the server is simply looking under a different key.

Both kinds of UUID feed the Locator Bar color algorithm perfectly happily, incidentally — the algorithm does not know or care which version it was handed. It just hashes the 128 bits. An offline-mode player still gets a stable color; it is simply a different color from the one they would have on an online server.

Renaming, and what stays fixed

Mojang's own systems are keyed on UUID rather than name, and the design shows it. The Wiki notes that "a player UUID is generated when the user purchases and registers a new Minecraft: Java Edition account" — it is minted at registration, tied to the account, not to whatever name the account happens to be wearing. Mojang removed the public username-history endpoint in September 2022, so the name is explicitly no longer treated as a historical record; the UUID is. And every server-side file that has to survive a rename — whitelists, ban lists, permission databases, player data files — stores UUIDs.

Straight answer: on an online-mode server, changing your username does not change your UUID, and does not lose your progress. Worth noting honestly, though: we could not find a single official Mojang page that states this in one sentence. The conclusion is drawn from how their APIs and data formats are built, not from a quotable line of documentation.

Java Edition profile names can be changed once every 30 days through the Minecraft.net account page.

Bedrock Edition does it differently

There is no Mojang-issued player UUID in Bedrock Edition. The Wiki is blunt about it: "the Xbox User ID (XUID, or Xbox services ID) is used instead as the unique identifier."

That has a direct consequence for the Locator Bar. In Java Edition the marker color is derived from the UUID and is therefore stable. In Bedrock Edition, per the Wiki's Locator Bar page, "the color is randomly assigned to the player at every session." There is nothing to look up, because there is nothing stable to look it up from. Any site offering a "Bedrock Locator Bar color finder" is selling you something that cannot exist.

Where UUIDs turn up in normal play

  • Target selectors. /tp 069a79f4-44e9-4726-a5be-fca90e38aaf5 ~ ~ ~ works, and unlike a username it cannot be spoofed by a rename.
  • Entity NBT. Every entity has a UUID tag in int-array form. Tamed animals store their owner's UUID under Owner; projectiles store the shooter's; dropped items store Thrower.
  • Player heads. The skin owner is recorded by UUID, which is why a head keeps the right face after the owner renames.
  • server.properties. resource-pack-id is a UUID identifying a server resource pack to clients.
  • The Locator Bar. The locator_bar_icon NBT compound on living entities stores a color integer and a style string, and in Java Edition the default color comes from the entity's UUID.

That last one is the reason this site exists. The full derivation — hash, byte extraction, shading, and a complete worked example — is on how Minecraft UUID color is calculated.

Common mistakes

Assuming a UUID identifies a person. It identifies an account. Alt accounts have their own UUIDs and their own Locator Bar colors.

Typing O for 0. UUIDs are hexadecimal: only 0-9 and a-f appear. There is never a letter o, g, or z in one.

Treating case as meaningful. Hex is case-insensitive. 069A79F4-... and 069a79f4-... are the same UUID and produce the same color.

Expecting a Bedrock gamertag to resolve. Mojang's username lookup covers Java Edition accounts only. A Bedrock-only name returns nothing, and that is correct behaviour, not an outage.

Mixing up the version digit with a version number of the game. The 4 in the third group is the UUID version. It has nothing to do with Minecraft 1.21.6.

Where to go next

References