How Much RAM to Allocate to the Minecraft Launcher

This is the one client-side question we answer in a server knowledge base, because it comes up constantly and because the two halves of it get confused with each other daily. "How much RAM should Minecraft have?" has two completely different answers depending on whether you mean the game on your PC or the server everyone connects to. This page is about the first one.

The second one — heap sizing, -Xmx, garbage collection, Aikar's flags — is Minecraft Server RAM and JVM Flags.

The Distinction, Stated Once and Clearly

Client RAM is a setting in your launcher, on your computer, controlling how much memory the game you are playing may use. You set it, it affects nobody else, and changing it does nothing whatsoever to the server.

Server heap is memory on the machine running the server. On a GameServerKings Minecraft server you do not set it at all: the launch command uses -XX:MaxRAMPercentage=95.0 and no -Xmx, so the heap ceiling is derived from your plan's RAM automatically and moves with it. There is no MEMORY variable and no Xmx field on the Startup tab. The editable variables are Framework, Minecraft Version, Build Number, Server Jar File, Extra Flags and Accept Mojang EULA — and none of them is memory.

Giving your client more RAM does not give the server more RAM

They are separate machines running separate Java processes. If your server is running out of memory, or lagging, or printing Can't keep up!, nothing you do in your launcher will change it — see java.lang.OutOfMemoryError: Java heap space and Diagnosing Minecraft Server Lag. Equally, if your game stutters while everyone else's is fine, that is your machine and a bigger plan will not fix it.

The rest of this page is entirely about your computer.

How Much Your Computer Needs Overall

Before allocating anything to the game, check that the machine has the memory to spare. Mojang's published requirements for Java Edition:

Integrated graphics needs more system memory because the GPU takes its video memory out of it. That is also why the "just give it 8 GB" advice you see on forums is actively harmful on a 16 GB laptop with an iGPU: Windows, your browser, Discord and the GPU are all drawing on the same pool.

How Much to Allocate to the Game

The wiki's guidance is short and correct: "Minecraft runs best with 2-4 GB of memory… Be sure to leave memory for the system and other programs!"

Two rules bound all of it:

1. Never allocate more than about half your system RAM. The Java heap is not the whole cost of running the game — the JVM, native libraries, the GPU driver and the operating system all need memory outside it. Overshoot and the machine swaps to disk, which the wiki names directly as a cause of intermittent stutter.
2. More is not better past the point where it is enough. Every garbage collection has to walk the objects that are alive, and a larger heap holds more of them. Going from 4 GB to 12 GB on a vanilla client does not raise your frame rate; it lengthens the pauses when the collector runs.

The honest answer for most people is "you have already allocated enough"

Low frame rates are almost never a memory problem. Render distance, shaders, resource pack resolution and the GPU are what set your FPS. Memory shows up as stutter — brief freezes, unrelated to what is on screen — not as a consistently low number. If your FPS is steady and low, changing the allocation will do nothing.

Where the Setting Actually Is

The official Minecraft Launcher. Memory is not a slider; it is a JVM argument on the installation.

1. Open the Installations tab.
2. Hover the installation you play and choose Edit (or the ellipsis, then Edit).
3. Expand More Options.
4. Find JVM arguments. Change the number in -Xmx, keeping the unit letter: -Xmx4G is four gigabytes, -Xmx6G is six.
5. Save, and start the game from that installation.

The same screen also holds Java executable — which defaults to the bundled runtime and should normally be left alone, because the launcher supplies the correct Java version for you — and the game directory and resolution.

Edit the number, not the whole line

The default JVM arguments contain garbage-collector tuning as well as -Xmx. Pasting a random flag set from a video over the top of them is the most common way people make their client worse. Change the one number. If you want a different flag set, apply it deliberately and change one thing at a time.

Third-party launchers — Prism Launcher, ATLauncher, GDLauncher, MultiMC and the CurseForge and Modrinth apps — all expose memory as a plain field, usually per instance, under a Java or Memory settings page. Per-instance is genuinely better: a modpack instance can have 8 GB while your vanilla instance keeps 3 GB, instead of everything inheriting one number.

Note that the installation is per-profile. Editing one installation's arguments does not touch another. If you changed the setting and nothing happened, check you are launching the installation you edited.

Checking Whether It Worked

In game, press F3 and look for the Mem: and Allocated: lines. Mem: is the percentage of memory in use and the used-over-total figure in MB; Allocated: is how much of the maximum the game has claimed so far. The total on the Mem: line is your -Xmx. If it did not change, the launcher is not using the installation you edited, or the argument was mistyped. (1.21.9 trimmed the default debug screen and made its sections individually configurable, so the memory rows may simply be switched off. Open the Debug Options screen with F3 + F6 and enable memory.)

The same screen tells you whether memory is your problem at all. Watch the number while you play:

• It climbs, drops sharply, climbs again — normal. That is the garbage collector doing its job.
• It sits near the ceiling and the game freezes for a second at a time — the allocation is too small for what you are running. Raise it.
• It sits at half the ceiling and the game is still slow — memory is not your problem. Lower the render distance and turn off shaders.

What Client RAM Never Fixes

Worth listing, because these arrive as support tickets weekly:

FAQ

Do I need to allocate more RAM to join a modded server?
Yes, and this is the one case where the answer is unambiguous. Every player needs the same mods installed locally, and those mods cost client memory. Use the figure on the pack's own page.

Does allocating more RAM increase FPS?
Not once you have enough. It reduces stutter caused by collection pauses; it does not make frames render faster.

Should -Xms and -Xmx match on the client?
On a dedicated game server, yes — that is PaperMC's guidance for the server side. On a desktop that is also running a browser and a voice client, matching them means the game claims its whole allocation at startup and never gives it back. Leaving -Xms alone is fine.

My server plan has 8 GB. Should my client have 8 GB?
No, and the two numbers are unrelated. Server memory is sized by player count, view distance, plugins and world size; client memory is sized by your mod list. See Minecraft Server RAM and JVM Flags for the server side.

The launcher says Java 25 is required. Do I need to install it?
No. The official launcher supplies the correct Java runtime automatically. Third-party launchers usually offer to download one too.

What to Read Next

• Minecraft Server RAM and JVM Flags — the server side, and why there is no -Xmx on your server
• Diagnosing Minecraft Server Lag — telling a server problem from a client one in about five minutes
• "Can't keep up! Is the server overloaded?" — what that console line actually measures
• java.lang.OutOfMemoryError: Java heap space — when it is genuinely the server's memory
• How to Install a Minecraft Modpack Server — pack-specific sizing on both sides
• Minecraft Players Can't Connect — the connection errors people blame on memory
• Updating Your Minecraft Server — the Java 25 change, which affects the server as well as the client

Primary sources used for this guide (all checked 19 August 2026): Mojang's published system requirements for Minecraft: Java Edition; the Minecraft Wiki on the Minecraft Launcher, Java Edition system requirements and improving frame rate and the debug screen; and the GameServerKings Minecraft (Java) startup configuration from our own panel.

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