KYSTEK LAUNCHERSomething broken? Let's get you back in the game.
Most problems have a two-minute fix — start with the common ones below. If none of them match yours, send it over and it lands in front of a person, not a ticket queue.
Kystek is run by one maintainer. Discord is usually same-day; email within a day or two.
The nine things that go wrong most often.
Ordered roughly by how often they land in the inbox. Each one is the actual fix, not a "have you tried reinstalling".
I can't sign in — the Microsoft code doesn't work
Device codes expire after about 15 minutes. If the browser tab sat open while you did something else, the code is stale even though it still looks fine.
- Close the sign-in window in the launcher and start it again to get a fresh code.
- Enter it at
microsoft.com/linkwhile the launcher is still waiting on that screen. - Approve the Xbox Live permission prompt if one appears.
If it gets past the code and then fails, the account itself is usually the issue: Kystek needs an account that owns Minecraft: Java Edition. Bedrock-only accounts, and Game Pass accounts that have never launched Java Edition even once, have no Java profile to return and will stop at that step.
Your password never reaches this app either way — sign-in is delegated straight to Microsoft, exactly like the official launcher.
A pack won't finish syncing, or the download stalls
A stalled sync is nearly always a half-written file rather than a broken pack.
- Quit the launcher completely and reopen it. Anything incomplete is refetched from scratch on the next sync.
- Start the sync again and let it run without switching packs mid-way.
If it stops on the same mod every single time, that file's upload is probably corrupt. Tell the pack owner which filename it stops on so they can re-upload it — they can see and replace individual mods from the pack's Mods tab.
Already-synced packs replay offline, so a sync that fails partway doesn't cost you the copy you already had.
Minecraft crashes right after I hit Play
Open that pack's logs/latest.log (see where the logs live) and find the first line starting with Caused by. That line names the actual culprit; everything above it is noise.
Three causes cover almost all of it:
- One incompatible mod — the crash names it directly. Ask the pack owner to remove or update that mod.
- Wrong loader version — a Forge pack opened against a NeoForge install, or vice versa. Re-syncing the pack repairs the loader.
- Not enough RAM — a modded pack that dies during "Loading mods" usually wants 4–6 GB. Raise the allocation in the launcher's settings; going above 8 GB rarely helps and often hurts.
Send that Caused by line with your message and the fix is usually one reply away.
It says Java wasn't found, or the wrong Java version
The launcher looks for an installed Java first and downloads a matching runtime when it can't find a suitable one, so seeing this at all normally means the download was blocked, not that you need to go install a JDK yourself.
- Check whether antivirus, a firewall, or a school/work network blocked the runtime download, then relaunch.
- Still stuck? Install a JDK yourself — Java 21 for Minecraft 1.20.5 and newer, Java 17 for 1.17–1.20.4 — and point the launcher at it in Settings.
Version mismatches ("class file version 65.0") mean the pack needs a newer Java than the one selected, not a reinstall.
I joined a pack but the mods aren't there
Joining a pack and installing it are two separate steps. After joining, open the pack and let the first sync finish — that's the step that actually pulls the mod files down.
If the mods are present in the launcher but missing in-game, you almost certainly launched Minecraft from the official launcher instead of Kystek. Each pack is its own isolated install; only launching it from Kystek uses that pack's mods folder.
The launcher won't update, or reopens on the old version
Updates are downloaded in the background and applied on the next full restart — not on closing the window to the tray.
- Quit the launcher fully, confirm no
Kystek Launcherprocess is still running, then reopen it. - If it still reports the old version, reinstall over the top from the download page. Your packs, settings, and sign-in all live outside the install folder and survive it.
I can't join a private pack
Private packs are invite-only by design. Depending on how the owner set it up you'll need either the pack's join password, or the owner to approve your join request from their Members tab.
A request that stays pending is waiting on a human, not on a bug — the owner sees it in the pack's Requests list. Public packs are joinable straight from My Packs with no approval at all.
Windows SmartScreen or antivirus blocked the installer
The Windows build isn't code-signed yet — a certificate costs more per year than this project spends on everything else combined — so SmartScreen shows an unrecognised-app warning on first install.
If you'd rather not click through that, that's a completely reasonable call. If you do: More info → Run anyway. Only ever install it from kystek.com or the download link on this site; a copy from anywhere else isn't ours.
How do I delete my account or leave a pack?
Both are self-serve — you never have to email anyone to be forgotten.
- Leave a pack: from the pack's page, or from My Packs.
- Delete your account: the launcher's Account page. If you still own packs, you'll be asked to transfer ownership or delete them first — deleting an account can't leave a pack ownerless.
What's kept and what's anonymised afterwards is spelled out in the privacy policy.
Grab the log — it turns a guess into a fix.
Two different logs, and they answer different questions. Paste whichever matches your problem into the form below.
The launcher's own log — sign-in, syncing, updates
On Linux: ~/.config/mc-launcher/logs/main.log
The game's own log — crashes, missing mods, Java errors
On Linux: ~/.config/mc-launcher/packs/<pack-name>/logs/latest.log
Paste in the last 50 lines or so rather than the whole file — the end is where the failure is. Logs can contain your Minecraft username and file paths; they never contain your password or session token.
Still stuck? Pick whichever suits you.
All three reach the same person. Discord is fastest, email leaves a paper trail, and the form below is the one that prompts you for the details that speed things up.
Best for anything back-and-forth — a crash log you're not sure how to read, or a sync problem that needs a couple of questions.
Email[email protected] — for account and privacy questions, anything you'd rather not put in a chat, or long log dumps.
Report a pack or playerAbuse, stolen content, or a member behaving badly? Report it from inside the pack itself — it reaches the moderation queue with the context attached.
What turns a two-day thread into one reply.
- The exact error text — a screenshot of the message beats a description of it every time.
- Which pack, and whether it's one you own or one you joined.
- What you'd already tried — so the reply doesn't start with something you've done twice.
- Whether it's ever worked — brand new install, or working yesterday and broken today? Different problem entirely.
- Your OS — Windows or Linux, and roughly which version. The diagnostics checkbox above covers this for you.
- The last 50 lines of the log for anything crash-shaped. See where the logs live.