Browsercraft: Java Minecraft in the browser

We have come full circle #applets

Twenty years ago running java in the browser would have just been called "using the internet"

This is the main way I used to play Minecraft in the Beta days, thanks!

Yep, the original Minecraft ran in the browser in a Java applet so this is particularly fun example. Though obviously there are significant security benefits to the JVM running within the browser's WASM sandbox instead of directly on the host.

Wow, same here, but I somehow completely forgot about that!

Huh, is Minecraft Java edition free now? I haven't played in a long time but I thought when you download the regular client you only get to play after signing in with an account that purchased the game, how is this thing just starting the game directly?

> there are significant security benefits to the JVM running within the browser's WASM sandbox instead of directly on the host.

The JVM originally also had the goal of providing a security boundary, and even had a relatively complicated permissions/security model enforced via call stack inspection.

That security model was ultimately too complicated for developers to work with, but I don't think the sandbox itself was particularly insecure.

It crashed for me :(

    [failed to get system properties (java.lang.RuntimeException: No OpenGL context found in the current thread.)]

Applets were a real vibe. The gradient-blue UI that came out of the box is true nostalgia.

Playing Minecraft without Microsoft account? That doesn't look safe.

You could always play Minecraft without an account. But you can't join most servers that enable authentication checks

Java Applets gave Java a bad name. Java was that thing that made web sites grind to a halt.

Why?

Nope, this is piracy. Which you may or may not consider a bad thing, but there will be lawyers in this person's future.

It's safe for the player, unsafe for the one hosting it, who risks prison time.

Well yeah you could play without an account with a cracked launcher

> Clicking the button below will download the client from mojang.com. By clicking it, you agree to the Minecraft EULA.

It's literally just downloading the client from https://piston-data.mojang.com/v1/objects/4a2fac7504182a97dc... where mojang makes it publicly available.

It's an older version so it's not linked on their website anymore, but you can find the same download link on the wiki: https://minecraft.wiki/w/Java_Edition_1.2.5

What makes you think they will have "lawyers in their future"?

My recollection is that the SecurityManager was notorious for being relatively easy to work around. Definitely one of the common questions people had when working on the richer HTML5 APIs was "how is your sandboxing going to be more effective than the Java applet model, given that that's known to be full of holes?"

how to do fullscreen?

Downloading a publicly available jar (https://piston-data.mojang.com/v1/objects/4a2fac7504182a97dc...), that gets linked on the minecraft wiki (https://minecraft.wiki/w/Java_Edition_1.2.5) and running it unmodified is "risking prison time"?

It's running minecraft 1.2.5 which was released in 2012, which mojang still makes available

A long time ago I looked for a way to download Minecraft to install on systems without any internet connection and it just wouldn't work. I even tired alternate launchers, but eventually gave up. Maybe the situation has changed and it's possible now though.

Depends on if the free trial is misused here somehow. I don’t know if it is.

If it had come out of Google or Microsoft maybe even Apple, the JRE would have been integrated into the browser much more efficiently and it would have been no slower than Javascript

But I don't remember Applets being particularly slow even back then, if you had a decent internet connection and they were written by a decent SDE

There is no circumvention of any access controls.

5 years ago, I watched a YouTube recording of a meetup talk given by one of the CheerpX engineers:

https://www.youtube.com/watch?v=7JUs4c99-mo

In it, they showed a functional demo of porting an OSS multiplayer C++ game entirely to the browser with WASM.

Afterwards, I read some of their engineering content and was blown away.

It's been fascinating to watch the CheerpX/CheerpJ progress from afar over the years.

I wrote a lot of applets back in the day for little graphics experiments and such, somewhat inspired by Ken Perlin's homepage[1]. I found that it's quite possible to make applets that load fast and run fast if you care about those things while building it and do some profiling. If you pull in hundreds of megabytes of libraries and trigger a GC every second then of course it will be slow.

[1] https://mrl.cs.nyu.edu/~perlin/

There's a very funny story behind MinecraftForFree.com which is what most people used back then.

Notch (the creator of minecraft) was angry someone was posting his game online for free. He emailed the owner, Dylan, of the site threatening legal action.

Instead of going down a legal route, Dylan challenged him play a game of quake3 to settle the dispute.

If notch won, Dylan would take the site down. If Dylan won, notch would would leave him alone and let him keep hosting the site.

Notch agreed, won the match, and Dylan followed the promise and took it down forever!

Until they want features and punch holes in the sandbox.

Audio/video codecs are a great example.

When I was in fourth grade, I'd take the half a mile walk to the library almost daily which always made my parents happy because they assumed I was going to read, but instead I was hopping onto their computers, going to http://minecraft.net, and playing minecraft on IE :)

Thanks for the nostalgia

Funny enough, the original version of minecraft used to run in the browser too! It used Java applets. That was a long time ago, I remember playing it as a kid

There are even recordings of their match (in two parts), they're quite funny: https://www.youtube.com/watch?v=g_Fu0SZ7PN8

The craziest part is that it executes on my iPhone SE 2020 in Safari. Textures work, shading works, pretty insane. I even managed to break a block.

Yes that's how notch was able to distribute it while circumventing publishers. Very smart move at the time.

There already is Minecraft in the browser implementations that are quite performant

https://map.realismc.com/#world:-87986:65:-25312:0:-0.01:1.5...

This is a world featuring llm powered players that make their own plans and constructions (using the terminal)

> If Dylan won, notch would would leave him alone and let him keep hosting the site.

Small correction, Dylan always planned to take the site down. They were playing for Minecraft capes[0] for him and his two teammates. The original livestream of the match is still up on Twitch also.[1]

[0] Cosmetics that used to be very rare and only given out by devs or at MineCon

[1] https://twitch.tv/videos/38469359

I get that when my GPU is disabled, although it usually falls back to CPU...

The longevity of Minecraft blows my mind. I was always aware of its existence but never looked into it. Now my kid is getting into it. So many generations of kids! It's incredible really.

That said, it has been a little sad digging into the current state of Java vs Bedrock, Bedrock iPad vs Bedrock Switch. The platform ubiquity is wonderful and the tradeoffs are what they are. But if folks were able to create a touch-capable web-powered Java Minecraft that would be a great fit for the iPad.

Thanks for your kind words, appreciated.

Link to our blog, we try to regularly publish high quality content: https://labs.leaningtech.com/blog

At first, there was no launcher there was just the Minecraft.jar file which you could launch to start playing. That's what the parent page is doing; it's just having us download and run the game, no need for a launcher.

Great. We brought back Applets.

It's too bad that this kind of thing is using x86 as the actually-pseudocode for this. I understand why -- ease of porting, etc. -- but using either WASM (w/WALI?) directly with a kernel compiled to WASM (there are efforts to do this) or something open like RISC-V would be better long term.

The children yearn for the mines, apparently.

Mobile is indeed supported, although the performance is not yet as nice as we would like.

The trickiest issue is input, since the "look around with your mouse" interaction maps very poorly on a mobile platform where "mousemove" implies touching / clicking.

We plan to eventually figure out a mobile-optimize UX, but we will most likely prioritize improving the performance first.

Neither decent internet connections nor decent SDEs programming Applets ever happened in the 1990s.

One can get early Alpha and Beta versions of Minecraft through the official launcher too. I think this is a nice benefit - you buy the game once and have perpetual access to the latest version, but also all the old versions which are worth playing for various reasons e.g. Beta 1.7.3 is very popular because it's one of the last versions before the terrain and cave generation was significantly changed.

Lawyers and judges care about the overall effect of a thing, not the technical steps you take to make it happen. The overall effect is: Someone goes to your website, and plays Minecraft for free. Therefore you gave them the service of playing Minecraft for free. Which is illegal.

The fact that the file comes from Microsoft's server is one of those "technicalities" that you've heard about some people sometimes, but not usually, getting off on.

Microsoft will probably argue that the login prompt is a technological protection measure, which makes it blanket illegal to work around, due to the over-broad DMCA. That technicality is about as likely to work against you, as the "it's from their server so I didn't distribute it" technicality is to work for you...

Mandatory disclaimer: I am not a lawyer and this is not legal advice.

There's also Eaglercraft, which achieves the same result, but it has functioning multiplayer, and runs up to version 1.8.9, though you'll need a beefy computer.

Due to the over-broad nature of the DMCA, almost anything is an access control that you aren't allowed to circumvent.

This is actually running on top of a WebAssembly-based Java Virtual Machine (CheerpJ).

You are probably thinking about our independent x86 virtualization product CheerpX (https://cheerpx.io)

The fact I'm playing this at 20 FPS on Firefox with a RX 7600 shows how much web browsers have regressed in 10 years, not how much they've advanced.

Hi everybody, happy to see our CheerpJ demo is appreciated.

CheerpJ is a WebAssembly-based JVM that can run unmodified Java 8 and Java 11 applications. Java 17 will be supported later in year.

I am the lead developer of CheerpJ and CTO of Leaning Technologies. AMA.

It's basically java -> wasm/webgl -> your computer

A 10 times hit compared to a native C implementation on performance doesn't really matter anymore, but a compounded 10x10 times will.

Cool stuff!

Hey I saw a typo on https://cheerpj.com/cheerpj-core-licenses/, it says "liencesees" halfway the page

Also Modded Minecraft is extremely popular, and the mods necessarily aren't version agnostic, so you need to be able to run a specific Minecraft version to play the pack of mods you're currently enjoying.

Right now I am playing Enigmatica 2: Expert, which is a mod pack for Minecraft 1.12

Today I need to teleport to my spaceship which is in orbit around a distant planet and then fly it back to our solar system and visit Mars, as I have neglected to obtain materials from Mars which I need to build this end game item I'm working on.

It's still recognisably Minecraft even though I'm working with a 9x9 crafting grid. It has internal consistency, dragons hoard rare metals, Plutonium is a rare metal, therefore make sure to bring hazmat handling equipment if you're about to plunder a dragon's hoard.

> The fact I'm playing this at 20 FPS on Firefox with a RX 7600

Vanilla Minecraft is known for being awful for FPS even outside of a browser. There's a reason most people use a whole slate of performance mods just to get actual decent performance.

(I've got a Ryzen 7 with a 3080 and it would frequently hover between 40-50fps even with graphics turned down. Install the performance mods and I can get >120fps with fancy graphics and shaders.)

Thanks for spotting this, we'll get it fixed ASAP

Now we just need to popularize Swing again and we'll be golden

Minecraft back in the day was a Java applet, so the game was running in a native JVM. This demo is running the game in a WebAssembly JVM, so performance is absolutely going to suffer. If the game were actually written for the web platform, it would perform significantly better.

Java Applets weren't some magical "workaround" for distributing without publishers, lots (well, subjective) of indie developers were distributing binaries via websites at the point of the first alphas of Minecraft. Of course, way more popular nowadays as there are dedicated platforms for it.

Would it work for a JavaFX app? (not sure I'd be able to shrink the bundle size enough for it to make sense though)

Same. I built a lot of animations with applets back in the day and if you avoided dependencies (other than what ships with the JVM) and your code wasn't ridiculous, you could get some pretty damn good performance out of it (minus initial load time which did tend to be suboptimal, but manageable). Applets were a pain in many ways but I think the tech gets blamed unfairly for bad performance.

I got into Minecraft via 4chan, of all places. People used to make posts about it and how cool it was and others would naturally talk crap about the game.

I get similar performance in Chrome on my phone (Pixel 7a). Perhaps this just runs poorly in Firefox?

JavaFX is not yet supported, but we plan to get it to work soon.

The issue here is that there is very little Java in JavaFX, it's mostly native C++ code. This makes it actually quite similar to the LWJGL library used by Minecraft.

Our plan is to use for JavaFX the same technology we have developed for LWJGL.

Start with suing the minecraft wiki then I guess

Also you should probably advice mojang to put some authentication on their download URLs, which have been publicly documented for more than a decade by now.

There is no login prompt. This project is over a year old. You are just misinterpreting the situation. This is like threatening to sue Mozilla because you can use Firefox to click on a download button, or Microsoft because double clicking on an exe on Windows runs the application.

An interesting fact about Minecraft is that when it came out, storing the block IDs for the loaded area used up a big chunk of your computer's RAM and had to be optimized as much as possible. So it was 8 bits per block space, and when they expanded to 12 bits, they added on another array with 8 bits per 2 spaces.

Now, it doesn't even use block IDs any more. It uses one whole object per block type, one pointer to one of those objects per block space, and has a lot more block types. The on-disk format stores the entire string name of the block, once per 16x16x16 region it occurs in.

the initial scope of minecraft was also in line with the java applet games of ~2005, like the ski simulator. minecraft came well after the applet era, almost to the end of the flash.

huh. Minecraft is the taylor swift of video games. the last big star before big tech took over discovery and access for an industry.

It's basically LEGO, it tickles the mind. Which is ironic, because LEGO Worlds isn't nearly as inspiring as Minecraft.

well Wasm had the promise of giving near native speed, but since they still don't offer direct write/share of memory it results in abysmal FPS.

I used to love Minecraft as a kid until my kid ruined it for me. This 5-year-old loves to be in Creative mode and put me in Survival mode and set up traps and rounds of enemies for me to fight my way out. Not relaxing at all anymore.

My 7 year old's favourite activity in Minecraft is to blow stuff up. I don't know whether to be concerned or not, but at least we've convinced him that it's really not cool to blow other people's stuff up.

Like you say, not very relaxing.

It's not full circle. It's using built-in browser capabilities instead of a special sideloaded runtime granted by a browser extension.

An example of full circle would be if wasm apps needed a browser extension so that they could access APIs not allowed by the browser.

No, I'm thinking about porting the Linux kernel to WASM itself and not using a VM written in WASM but WASM directly:

https://wasmlinux-demo.pages.dev

In other words, using WASM as if it were the CPU architecture in the VM.

+1 for Eaglercraft. It's based on the open source TeaVM project ( https://teavm.org/ ), which transpiles Java to JS or WASM to run efficiently in modern browsers. With numerous shipped production Java-in-the-browser projects, TeaVM is my preferred option for Java in the browser thanks to its performance, build speed, and Apache license.

Got any resources on this? As a kid I never thought about it but as a programmer, I always wondered how you scaled up these kind of problems.

My source is the code itself, but you could also use the wiki's documentation about the on-disk data format.

It's fundamentally just a big array of one entry per block space. It was never too big for an average computer to handle - otherwise Minecraft wouldn't have been able to exist yet (maybe that's why it didn't exist until the time that it did) but they've gotten a lot less efficient since then, in the name of flexibility.

Before Minecraft existed I played Cube 2 on "coop edit" mode. Its world structure is an optimization you might be interested in: it represents the whole game world (of fixed size) as an octree. So the map starts as a node with 8 child slots (one for each corner of a cube); each is either completely solid, completely empty, or another node, recursively down to some maximum depth. Therefore Large empty areas and large solid areas are stored in about the same amount of space as small empty areas and small solid areas.

Very astute comparison. Yet somehow still both huge!

Send that child to the demolition career. There’s good money in blowing up buildings!

This is a 20-ish year old game. It really shouldn’t matter.

Exactly! There is a demand for constructive deconstruction.

Consent is everything?

This implementation isn't using webworkers either. Moving the java VM to a webworker would likely improve performance 10 fold.

I used to do that except it was to play Runescape lol. The local library got some really nice Pentium 4 computers too.

Another comment mentions MinecraftForFree.com...

In middle school, in an attempt to get around the school firewall, I copied the HTML code from that website to my own to play Minecraft at school. Since my domain wasn't on the blocklist, it worked! But when my friends started using it to play, even after they hadn't bought the game, I resolved to add a login wall.

I built a backend proxy in PHP that would POST their credentials to the Minecraft API to make sure they had purchased the game. I still think it's funny to think I had no ethical qualms about circumventing the school firewall, but piracy was where I drew the line.

We've gone full circle! Java was originally created to run apps in the browser.

And in the meantime, this shitty Roblox still doesn't run on Linux...

A longstanding performance effecting bug was fixed in the recently released 1.21.5 and the difference is night and day at least for vanilla clients.

This one: https://bugs.mojang.com/browse/MC/issues/MC-170134

I now never see below 60 fps when for all my years of playing this bug would bring down my FPS to the teens or 0 all the time no matter what hardware.

How much is the licensing for a small company wanting external users to use it to use an app hosted online?

... no, it is not like that, and I can't help you.

There's a similar but "illegal" other client called eaglercraft. It bumps this up a notch with a much more "recent" version of MC, by compiling java to javascript

Small Business licenses will be available with the release of CheerpJ 4.0, expected in mid April 2025.

They will allow self-hosting and will be priced on a per application / per website basis. They will be priced to be affordable and ensure that CheerpJ enjoys a wide reach.

If you are interested before the release, please do get in touch (info@leaningtech.com).

Yes. Downloading a game file you don't own and running it is called piracy, so beware of possible legal ramifications.

thanks! that's kinda what I figured. And now it's not part of Java's "core" so it'd make sense if it was "out of scope"

I set up two old computers to play some Minecraft with my youngest kid. Unfortunately it turns out recent versions are much slower than old ones. I have not bothered to bisect it to figure out exactly what version(s) killed performance. My weakest old computer can run the latest version with 1-2 fps. It can run 1.12 with at least around 30-40 fps, which is more than enough for me to be able to enjoy the game (being old enough to have grown up in an era when we were happily playing flight sims at 5-10 fps). Anyway it is nice that the launcher makes it possible and easy to go back and play older versions. I much prefer drm-free games, but at least supporting old versions like this is better than 99% of games.

Is this at all related to Eaglercraft (web: https://eaglercraft.com/, src: https://git.eaglercraft.rip/eaglercraft), which is also browser-based Minecraft?

Older versions of Minecraft are better; they've added too much junk to newer versions. I stick to 1.6.3, 1.7.10, 1.12.2. Heard they added a bunch of telemetry and ban capabilities in 1.18+, for which mods are needed.

DRM-free Minecraft launchers exist, mostly forks of MultiMC5. Now if only offline installers existed...

No, this is the unmodified Minecraft JAR running on top of CheerpJ, a WebAssembly-based JVM.

Also, Minecraft is like a gateway drug into Factorio. Dangerous stuff!

> A longstanding performance effecting bug was fixed in the recently released 1.21.5

Good to know that they're finally considering performance fixes but obviously involves moving to 1.21.5 and until there's mods to disable the bits I don't like, I'll be sticking with 1.20+mods.

Ah cool I didn't know, I thought the download of the actual full client was gated behind a login since even third party launchers seemed to require you to log in to play, good to know!

Good thing no one is asking you for "help". You're the one threatening FUD without anyone asking for it. Go bother someone else with your nonsense, lol.

This looks amazing! Both Eaglercraft and Browsercraft (though Eaglercraft seems to be further along) — the closest realization to the dream I've had for years of running a fully-featured Minecraft in the browser. Quite promising, I can only wonder where these projects will end up as they develop further, wishing for the best...!

Why is this so exciting to me? I started playing Minecraft back in the Java modding days, which really picked up steam around 1.2.5 and, by my estimations, peaked around 1.7.10. There was a veritable cornucopia of mods widely available, to enhance the game in a plethora of ways. I modded my game so hard I undoubtedly ran more third-party code than first-party/Mojang. Minecraft was a platform for creative expression, freeform and unconstrained. The golden age of Minecraft modding!

But it wasn't all unicorns and rainbows. There was a dark side of modding: the ease of use, or lack thereof in getting mods setup. Modpacks helped, but you still had to run untrusted code, and you still had to have a compatible PC. This is what (nearly) killed Minecraft for me. I wanted to play with my friend, but his PC had Windows upgraded and lost Java or OpenGL compatibility, and he eventually dropped his desktop and switched to tablets, phones, and consoles. My highly curated developed modded technical world became inaccessible.

Contrast this unfortunate situation with the browser: with "load and go" functionality as Douglas Crockford calls it, you can just visit a website and play, provided sufficient specs. What if we could play modded Minecraft (preferably 1.7.10), with all the mods to our hearts content, right in the browser, accessible to anyone?! And anyone could develop and distribute their own mods without concern, being safely executed within the browser sandbox.

I don't know how close Eaglercraft is to this utopia, but I find the possibility very enticing.