Downloads & mirrors

Slow downloads are usually not the launcher's fault. Switch the download source first, then look at thread count and speed limits.

Download tasks are queued

After you click "Download", the task goes into a queue and does not freeze the whole interface: waiting tasks can be removed with ×, a running task can be cancelled, and the queue continues after a cancellation.

The download page lists each task's state: waiting, downloading, done, failed.

File source vs version list source

Settings → Downloads → Download source has two independent dropdowns:

• File download source: client jar, assets, dependency libraries;
• Version list source: version manifest, version JSON, asset index.

Both offer the same four options:

Option	Behaviour
Prefer official, switch to mirror when slow	Default. Connect to official first; switch to BMCLAPI if there is no response for a few seconds
Prefer mirrors	On networks in mainland China, use the mirror directly
Prefer official	Official first, fall back to the mirror on failure
Official only	Official only; fail if official is unreachable

Custom file mirror

Settings → Downloads → Custom file mirror accepts a mirror root address (BMCLAPI by default, for example https://bmclapi2.bangbang93.com). Once set, the version manifest, client, libraries, and assets all prefer it, falling back to the normal source order if it cannot fetch.

Leave it empty for the default BMCLAPI.

Game directory

Settings → Downloads → Game directory lets you put versions, libraries, assets, and mods in any folder; leave it empty to return to %APPDATA%\gpcl\.minecraft.

Switching directories does not move existing files. Versions in the old directory do not come along; copy them yourself if needed. Configuration and logs still stay in %APPDATA%\gpcl.

Maximum threads

Default 64, range 1-128. With many small files, raising concurrency helps; too high and network equipment or the mirror may throttle you. Lower it when the network is unstable.

Speed limit

0 means no limit; once a value is set, all download tasks share this total cap, in MB/s, effective from the next download start. Lower it when several people share the connection.

This limit applies only to game asset downloads. The Java runtime uses a separate mirror and is not affected.

Java mirrors

Settings → Downloads → Java download offers Tsinghua University, Nanjing University, Huawei Cloud, or a custom mirror. If the selected source fails, the next one is tried automatically, with official Adoptium as the final fallback.

Custom addresses support two variables:

• {v}: Java major version, for example 8, 17, 21;
• {version}: the full upstream version number, for example 17.0.20.1_1, which changes as upstream releases.

Example:

https://cdn.example.com/java/{v}/OpenJDK{v}U-jre_x64_windows_hotspot_{v}.zip

When a download fails

1. Switch to another download source.
2. Lower the thread count to 32 or 16 and retry.
3. Make sure the system clock is correct - a large time skew makes HTTPS certificate validation fail.
4. Still stuck: send email with the newest log from %APPDATA%\gpcl\gpcl\log.