Minecraft 26.4 snapshots: what changes for server owners

Mojang released the first 26.4 snapshot on 22 September 2026, one week after 26.3 Wilderness Bound. Most snapshot coverage is about blocks and mobs. This one is mostly about servers, so here is what changed for the people who run them.

Snapshot	Released	Protocol	Data version	Java
26.4 Snapshot 1	22 September 2026	1073742163	5119	25
26.3 (current release)	15 September 2026	777	5023	25

The protocol number is why a snapshot player cannot join your 26.3 server. Snapshot protocols carry a high flag bit, so they never match a release number. Java stays at 25, so nothing changes on the machine itself.

Three new server.properties settings

All three are new keys in server.properties. Leave them out and the server behaves exactly as it does today.

allowed-connection-ids=
status-contact-details=
enable-legacy-status=true

allowed-connection-ids is a comma separated list of IDs. When it is not empty, the server only answers players who connect with a matching ID in the address. Players type it in front of the address with an @ sign, so [email protected] connects to play.example.com with the ID staff. Anyone without a matching ID gets rejected at the door, and they do not see your server's status either: no MOTD, no player count.

That makes it handy for a test server or a build server you do not want showing up to strangers. It is not a password. The ID is sent in plain text, and anyone who learns the address can use it.

status-contact-details is a free text field that gets sent along with your server status, the same data the multiplayer screen reads for the MOTD and player count. Mojang describes it as a way to reach the owners of a server that has no website. An email address or a Discord invite are the obvious uses.

enable-legacy-status controls the old status ping from before Minecraft 1.7. It defaults to true, so nothing breaks. If no one pings your server from a client older than 2013, you can switch it off. Note that enable-status still has to be on for any status to be sent at all.

Server addresses can now carry extra data

When a client connects, the first packet it sends includes the address the player typed. Until now that was only a domain name. From Snapshot 1 the address can carry extra values after a question mark, written like a web address: example.com?key1=value1&key2. The field grew to 1,024 characters.

Two details matter for server owners:

1. SRV records. If your domain uses an SRV record to point at another host, the address now contains both names. The resolved domain comes first and the original is added as an _o value with its port.
2. Transfers. The transfer packet, which moves a player from one server to another, can now attach its own values that the target server receives.

If you run a proxy or a plugin that routes players by the domain they typed, it reads exactly this field. Expect those tools to need an update before they handle 26.4 addresses cleanly, and test your routing on the snapshot before the release lands.

A mod list packet, empty for now

Snapshot 1 adds a minecraft:mod_list packet that a client sends at the start of the connection so the server knows which mods it runs. The vanilla client sends it empty, because vanilla has no mods to report. Filling it in is left to the mod loaders. Mojang says the goal is easier debugging: once loaders fill it in, a server owner can see which mods a player brought when something goes wrong.

Data packs and resource packs

The data pack version moves from 121 to 122 and the resource pack version from 97 to 98. For most packs a version bump is only a number in pack.mcmeta. These changes can break custom world generation, though:

• Noise settings lost default_block. The default is now always air. A pack that set stone or anything else there has to move that block into its material rules.
• The cuboid placement now means what it says. An xz_size of 2 used to make a 3 by 3 area and now makes 2 by 2. Packs tuned to the old behaviour will quietly place smaller features.
• fixed_placement needs at least one position.
• Placed features must stay within a 3 by 3 chunk area around where they start, and this is now checked.
• Biome entries in a multi noise source can no longer overlap on every parameter with the same offset.

The fillbiome command now fills biomes with block accuracy, which matters if you use it in build tools or maps.

Vulkan is now the default

In the video settings, "Default" now means "Prefer Vulkan". The game also stops switching the graphics setting on its own after a crash at startup. For players with older drivers that means a snapshot that fails to open will keep failing until they pick OpenGL by hand. Our Vulkan explainer and the OpenGL driver error guide cover what to do.

Old worlds get the new caves

Worlds created before Caves and Cliffs, which got deeper terrain added below them in 1.18, now also generate sulfur caves in that lower part when upgraded. If you run a long lived world from 1.17 or earlier, that area will change the first time it loads in 26.4.

Should you test the snapshot?

Test it, but never on your real world. Copy the world folder, run the vanilla 26.4 Snapshot 1 server jar against the copy, and treat that copy as lost afterwards. There is no supported way to open a world in an older version once a newer one has saved it.

For modded servers, a handful of projects already publish 26.4 snapshot builds, including Fabric API, Mod Menu and Simple Voice Chat. The 26.4 Snapshot 1 compatibility page lists everything that declares it, and it updates as authors publish.