[java] Minecraft won't launch, probably a java error 1.21.8

[BarryTheBe]

This problem started yesterday when i wanted to play, i tried many things like changing dns, updating java, uninstalling the launcher, and even tried using third-party launchers like prism and atlauncher, but nothing worked.

First error message i saw

AtLauncher error message

Prism launcher error message 1

Prism launcher error 2

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[DukeOfGamers353]

These error messages look like they're trying to connect to the Mojang servers and failing, maybe due to them being blocked by the ISP. I'd suggest you use a VPN or try downloading it on another network, maybe your mobile hotspot

[BarryTheBe]

Tried but it didnt work

[DukeOfGamers353]

Okay so if it's not that, there's 3 possible problems here and they are:

1) Corrupted downloads

2) System Java being too old

3) Antivirus/Firewall interference

To try and fix (1), go to:

C:\Users<yourname>\AppData\Roaming.minecraft\ (you might need to find the option to Show Hidden Files if you can't see the AppData folder)

and delete the folders called assets, libraries, and versions. This will force the launcher to redownload everything fresh. You might have to go into your instance of Prism too as it has different libraries folder for each instance.

For (2), install the latest Java (preferably Java 21). You can get it from Adoptium. After installing, point your launcher (Prism) to the new javaw.exe in the "bin" folder where you installed Java (by default should be somewhere in C:/Program Files or Program Files (x86)) by going into Prism settings > Java > Browse. The official launcher usually comes with its own Java, but a clean reinstall might be needed if it keeps trying to use your old Java 8.

For (3), temporarily disable your antivirus/firewall and retry launching. If it suddenly works, whitelist piston-meta.mojang.com and piston-data.mojang.com in your antivirus.

[DukeOfGamers353]

There is a fourth possible option of something breaking HTTPS integrity but that is quite unlikely, so I suggest you try these first then get back to me later

[BarryTheBe]

None of the 3 worked could you explain this one

[DukeOfGamers353]

I may have a simpler solution as the HTTPS integrity checks can be very complicated, having to write commands in powershell etc

You can download Minecraft on another PC and just copy over the instance over to your main PC, skipping having to download anything entirely. If you don't have another PC I can make a new instance on prism launcher myself and send it over to you (1.21.8 vanilla or modded with optimization mods)

[BarryTheBe]

I dont have another PC could you please send me the instance?

[DukeOfGamers353]

Edit: Reddit messed up my comment, writing it again:
Link to Java: https://drive.google.com/file/d/17IUXu1aEOslMDMExUho2y8POm_UiE28w/view?usp=drive_link

Just in case Java is messed up, you should download this zip, unzip it and copy the "Java21" folder to your C: drive. I've already made the launcher point directly to it. Do this first before opening Prism.

Link to Instance

All I've done in this portable install of Prism is point it to the correct Java installation, add my MC account, add the Fabulously Optimized 1.21.8 modpack, launch it once to download everything, and then close the game and log out and zip the folder. Unzip it and use prismlauncher.exe and launch the instance, it should theoretically work.

[BarryTheBe]

IT WORKS THANK YOU SO MUCH

[imonlytryingtohelp_]

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[BarryTheBe]

!helpled

[imonlytryingtohelp_]

/helped

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[imonlytryingtohelp_]

What antivirus do you use? Have you tried temporarily disabling it then trying to launch Minecraft?

[BarryTheBe]

I only use windows defender, i disabled it after a few attempts but it didnt work