DownloadClientJarEvent

Gets fired while the Minecraft client JAR is being downloaded.

Fields

progressdouble

The overall download progress as a value from 0.0 to 1.0

downloadedByteslong

The number of bytes downloaded so far.

totalByteslong

The total size of the client JAR in bytes.

When it fires

ClientDownloader posts this event on every chunk read from the HTTP response body (there’s no throttling like the Java runtime downloader has), plus one guaranteed final call with progress: 1.0. Since it comes from a single sequential InputStream read loop, unlike the asset/library events, these always arrive in order on one thread.

Two cases where you won’t see this event fire during a normal launch:

• The cached JAR is already valid. If path exists and its SHA-1 matches the expected checksum from VersionMetadataProvider, ClientDownloader skips straight to a single progress: 1.0 event without downloading anything.
• Offline mode. Launcher.launchMinecraft(...) only calls downloadClient(...) when context.isOnline() is true; in offline mode it either reuses the cached JAR silently or throws OfflineModeNeedsNetworkException if none exists - neither path posts this event.