Fix "Incomplete set of tags received"

A player is disconnected as they join, with "Incomplete set of tags received from the server. Please contact a server operator." A tag is a named group of game elements such as blocks, items or entities, and the tag #minecraft:logs stands for all log blocks. The message says the set of tags reached the player incomplete. This guide shows how to check the player's game and your server, and how to fix a mismatch. Of the versions we opened, only 1.16.5 and 1.17.1 have code in Mojang's own client that raises it, so the guide starts with the player's game.

Checked against Minecraft 26.3, using Mojang's own client and server files, October 2026.

What the message means

Mojang's language file words it as "Incomplete set of tags received from the server. Please contact a server operator." Older versions, such as 1.20.4, say "from server" and "contact server operator", but the meaning is the same.

Vanilla's tags are plain JSON files inside the server jar, under data/minecraft/tags. The file block/logs.json is the list of all logs. It contains other tags, such as #minecraft:logs_that_burn, which has its own file, block/logs_that_burn.json. Data packs supply tag files as well, and the first of the two log lines below names the pack when one of them cannot be read.

We opened the client files of several versions. Minecraft 1.16.5 and 1.17.1 contain code that raises this message. Minecraft 1.18.2, 1.19.4, 1.20.4, 1.21.11 and 26.3 contain none, so on a current version the message is not raised by Mojang's own client code. Look at what the player's game adds, starting with their mods.

Check what the player is running

Ask the player for their Minecraft version, whether they use Fabric, Forge or NeoForge, and a list of their mods. Open the JAR Manager under More to see what your server runs. The Minecraft version should match, and so should the loader.

If only one player sees the message, start with their game. Have them start a clean profile with no mods and try again. If it joins, add mods back in small groups.

If your server runs mods

1. Open Mods under Content and click Installed to see what the server has.
2. Click Export for players. It packs the mods players need into one zip with instructions and leaves server-only mods out.
3. The player removes their old mods and installs the files from that zip, so their versions match yours exactly.
4. If you changed a mod, open the Console tab and click Restart, then check Installed again for a Failed to load or Needs badge. Fix mod and plugin errors on Minecraft explains those.

If your server is Vanilla or Paper

Ask the player to try without mods that add blocks, items or recipes. If you also run data packs, check the Console for tag problems. Look for lines like these:

• Couldn't read tag list ... in data pack ... means a tag file could not be read.
• Couldn't load tag ... as it is missing following references means a tag lists something the game does not have.

Both lines name the tag, but only the first also names the data pack. Then:

1. Open Datapacks under Content and click Installed.
2. Click Disable on the pack named in the log. It is renamed, not deleted. If the line only names a tag, as the second one does, the log does not say which pack is at fault, so disable your data packs one at a time and check the log again after each.
3. Click Restart on the Console tab, then try joining again.

Match the versions

Whatever the cause, the player's client and the server should run the same Minecraft version, so change one of them if they differ. To move the server, use JAR Manager, as in Change your Minecraft version or mod loader. Fabric and Forge mods do not load on each other's loader without a bridge mod, which Can Fabric mods run on Forge? We tested it tested.