Java Client

The Java Client or Legacy Java Client was an Old School RuneScape client built by Jagex for desktop platforms. In the past, the client was an alternative to playing the game in a browser. However, due to multiple browsers discontinuing support for Java applets, Jagex was forced to drop support for browser play. The client does not support hardware acceleration, and is limited to 1 processor core and 50 frames per second.

The Legacy Java Client was no longer the default client on 20 July 2023 and was announced to be fully deprecated since 24 July 2024 despite getting updates up until 1 October 2025. As of 28 January 2026, the Legacy Java Client can no longer be used^[1], although it is still available for download from the Old School RuneScape website for Windows and macOS.^[2] It was possible to run the Java client on Linux, although not officially supported.

Historically, it was possible to modify the client to launch RuneScape Classic, RuneScape 3, DarkScape, and FunOrb games.

On Windows, the configuration is stored in the file %USERPROFILE%\jagexcache\jagexlauncher\oldschool\oldschool.prm

To edit this file, type %USERPROFILE%\jagexcache\jagexlauncher\oldschool into File Explorer's address bar and open oldschool.prm with Notepad. If you can't save, make sure the game is closed and try again.

On macOS, the configuration is stored in the file Runescape.app/Contents/Info.plist

To edit this file open Terminal and type the following:

open -a TextEdit /Applications/Old\ School\ RuneScape.app/Contents/Info.plist

-Djava.class.path=jagexappletviewer.jar
-Dsun.java2d.noddraw=true
-Dcom.jagex.config=http://oldschool.runescape.com/k=3/l=$(Language:0)/jav_config.ws
-Xmx384m
-Xss2m
-XX:CompileThreshold=1500
-Xincgc
-XX:+UseConcMarkSweepGC
-XX:+UseParNewGC
jagexappletviewer

The initial release of the Java client did not include the -Xmx384m Java parameter. If you delete it, the client will default to the minimum which is the equivalent of -Xmx256m.

Warning: Lowering the amount of memory used by the Java client can cause game instability and increase lag.

You can increase the amount of maximum heap the Old School RuneScape client uses. This can help decrease lag.

To do this, change -Xmx384m to a higher value; -Xmx512m is recommended.

Warning: Allocating too much memory to the heap can cause game instability. If your client begins to crash to desktop after increasing the amount of maximum heap, decrease the maximum heap size and try again.

You can choose a different garbage collector for the Old School RuneScape client to use. This can improve map loading times and decrease lag caused by garbage collection.

To do this, make the following changes to the client's configuration file:

• Remove the following flags

-XX:CompileThreshold=1500
-Xincgc
-XX:+UseConcMarkSweepGC
-XX:+UseParNewGC

• Add the following flags:

-XX:+DisableExplicitGC
-XX:+AggressiveOpts
-XX:+UseAdaptiveGCBoundary
-XX:MaxGCPauseMillis=500
-XX:SurvivorRatio=16
-XX:+UseParallelGC

Edit the flag adding the world you wish to connect to: -Dcom.jagex.config=http://oldschool.runescape.com/jav_config.ws

For example:

• Old School (world 330): -Dcom.jagex.config=http://oldschool30.runescape.com/jav_config.ws

Note: The world server number for some Old School RuneScape worlds does not match the actual world number. Hover over the world server links on World Servers List to find the correct number for the world you wish to connect to.

Enabling SSL connectivity can help decrease lag you if you're connecting via a mobile network, restrictive network, proxy, or firewall.

To do this, add one of the following flags to the configuration file:

-Dhttps.protocols=SSLv3

or

-Dhttps.protocols=TLSv1,TLSv1.1,TLSv1.2

Note: TLS 1.1 and 1.2 protocols are not available without the KB 314025 update on Windows 7. The use of SSLv3, TLSv1 and TLSv1.1 is not recommended unless your device does not support TLSv1.2 or you are experiencing connection issues.

-Djava.class.path=jagexappletviewer.jar
-Dsun.java2d.noddraw=false
-Dcom.jagex.config=http://oldschool.runescape.com/k=3/l=$(Language:0)/jav_config.ws
-Dhttps.protocols=TLSv1.2
-Xmx512m
-Xms512m
-Xss2m
-XX:+DisableExplicitGC
-XX:+AggressiveOpts
-XX:+UseAdaptiveGCBoundary
-XX:MaxGCPauseMillis=500
-XX:SurvivorRatio=16
-XX:+UseParallelGC
-XX:+UnlockExperimentalVMOptions
-XX:+TieredCompilation
jagexappletviewer

On macOS Mojave and later, you can enable the system dark appearance by editing the Info.plist configuration file using Terminal. Close the game client, then copy and paste the following to a new Terminal Shell:

plutil -insert NSRequiresAquaSystemAppearance -bool NO /Applications/Old\ School\ RuneScape.app/Contents/Info.plist

This will append the NSRequiresAquaSystemAppearance key to the configuration file with a boolean value of NO. To revert changes, simply change the boolean value to YES.

• 1.0.0 - Initial release.
• 1.0.1 - Fixed bug where Vista and 7 users need to disable UAC to be able to install client, added an options bar with a language setting on top.
• 1.0.2 - Uses its own interface instead of the default Windows style for the language setting. Client automatically removes the languages menu and copyright notification upon log in.
• 1.0.4 - Client scrollbar changed.
• 1.1.0 - Client update on 17 October.
• 1.2.0 - Possibly unsuccessful attempt to remedy lag problems after the bot nuke event.
• 1.2.3 - Fixed the removal of the languages menu and copyright notifications when logging in on Linux and Mac, plus providing a direct link for the jagexappletviewer.jar for use by custom clients like the RSU-Client and other Linux Clients.
• 1.2.4 - The client may now be launched directly from the website.^[3]
• 1.2.5 - Added support for the Local timestamps in chat box Interface setting.
• 1.2.6 - Fixed an issue that prevented use on mobile networks.
• 1.2.7 - Fixed scrollbars in adverts.

v t e Mechanics
Engine	Java RuneScript RuneTek
Game clients	Jagex Launcher Desktop Mobile Third-party RuneLite HDOS Discontinued OSBuddy Konduit Java
Performance	Bad luck mitigation Cache format Clickbox Drop rate Game square Game tick Line of sight Player identification number Stealth
Exploits	Run trick Tick manipulation Tick eating Drop trick Animation stall
Graphics	Interface Graphical updates (historical)
Servers	Server Ping Lag