Optimize Minecraft Resource Pack Size and Speed

Written for Minecraft 26.3.

To optimize a minecraft resource pack, cut what the player downloads and loads: remove unused files, shrink textures and audio, and keep models simple. Smaller packs download faster on join and are less likely to hit the server's size limit.

Before you start

• A backup of the pack. Some steps delete files.

• The pack as an unzipped folder, so you can check sizes.

• A way to host the final zip. See Pack basics for serving it.

Know the limit

The wiki states a server resource pack may not be larger than 250 MiB. That limit was 50 MiB, then 100 MiB in 1.15, then 250 MiB from 1.18. Aim well below it, because players on slow connections wait on the join screen.

Shrink the pack

1. Delete unused files. Remove textures, models, sounds and lang files that nothing refers to.

2. Lower texture sizes. A 512 by 512 texture used on a small item adds size and gains nothing. Match the size to how big it appears.

3. Reduce model elements. Fewer cubes load faster. Merge faces that are never seen.

4. Compress PNG and OGG. Re-export images with a lossless PNG optimiser and audio at a lower bitrate. Music can be stereo, but sound effects should be mono.

5. Remove duplicates. Reuse one texture across several models instead of copying it.

6. Strip metadata. Export images and audio without tags.

Use a packing tool

PackSquash is a command-line tool that optimises resource packs for you. Its own site says it reduces PNG colour depth and strips metadata, transcodes and downsamples audio to Vorbis, minifies JSON and shaders, and recompresses everything else, then builds the zip. It also validates files. Its site cites one pack going from 118 MiB to 57 MiB. Results vary, and some of its audio and image steps are lossy, so compare quality before shipping.

Host it and set the checksum

1. Upload the zip somewhere it can be downloaded directly.

2. Set resource-pack in server.properties to the link. Our server.properties tool lists the keys.

3. Set resource-pack-sha1 to the zip's SHA-1 in lowercase hex.

4. Optionally set require-resource-pack=true and resource-pack-id to a UUID.

resource-pack=https://example.com/packs/mypack.zip
resource-pack-sha1=<40 hex characters>
require-resource-pack=true

Get the checksum with shasum mypack.zip on macOS or Linux, or certutil -hashfile mypack.zip SHA1 on Windows. The sha1 lets the game check the download. A wrong value makes the server console print an invalid sha1 warning at startup.

Check it worked

1. Compare the zip size with the old one.

2. Join with a clean client and time the download.

3. Look at the client log for texture or sound warnings.

Common problems

The pack is rejected as too large

It is over 250 MiB. Cut audio first, as it is usually the largest part.

Players re-download on every join

The sha1 or the link changes between builds. Keep the link stable and update the sha1 when the file changes.

Textures look blurry after shrinking

Do not halve a texture that is shown big. Keep hand-drawn pixel art at its native size.

Merging packs doubles the size

See merging packs to avoid duplicated files.

Rebuild, then retest. Automatic tools can change files in ways that break a model or sound. Check your own pack in game.