Official Old School RuneScape client made cross-platform and portable. Saves all dependencies and game files to a self-contained directory.

• Supported platforms: Windows x64, Windows x32, macOS x64, Linux x64, Linux aarch64, Linux arm32
• Downloads ~200 MB on first run, uses ~40 MB total disk space afterwards (excluding game cache)

Download as .zip or .tar.gz and extract to the desired location

Execute client.cmd (Windows Batch file) or client.command (Shell script) to launch the client

jagexappletviewer.jar, jagexappletviewer.png, and legal/jagexappletviewer.LICENSE have been extracted from the official Windows client using the following method

curl -O https://www.runescape.com/downloads/OldSchool.msi
cmd.exe /c "msiexec /a OldSchool.msi /qn TARGETDIR=%cd%\msi"
cp msi/jagexlauncher/jagexlauncher/bin/jagexappletviewer.jar jagexappletviewer.jar
cp msi/jagexlauncher/jagexlauncher/oldschool/jagexappletviewer.png jagexappletviewer.png
cp msi/jagexlauncher/jagexlauncher/LICENSE.txt legal/jagexappletviewer.LICENSE
zip -d jagexappletviewer.jar MacOSXHelpers.class