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Minecraft Server Doctor

Drop your whole server folder, or its zip. This reads the log, the crash report, every mod jar's own metadata and your JVM arguments together, and tells you which file to change. Nothing is uploaded and there is no account. There is no upload limit because there is no upload, but the practical ceiling is your browser's memory: a zip is opened whole, ZIP64 archives need the folder picker instead, and the first 800 mod jars are inspected.

Drop your server folder or a .zip of it here, or

or a zip:

The more you include, the better the answer. logs/ plus mods/ is the minimum for naming a culprit file.

Why a folder and not a log

Every other analyzer takes one file, and that framing is why they stop at the exception. A log says NoSuchMethodError was thrown from com.simibubi.create.foundation.render.CreateRenderTypes. On its own that is a shrug. Your mods/ folder says that class lives in create-0.5.1.jar. That jar's own mods.toml says it requires flywheel [0.6.10,0.6.11). And the folder says flywheel-0.6.9.jar is what is actually installed.

Four facts, one sentence: replace flywheel-0.6.9.jar. Do not add RAM, do not change Java. That is the whole reason this reads a folder.

What it will not do

It will not tell you a mod is broken when it cannot prove it. A dependency range it cannot parse is reported as unknown, never as a mismatch, because sending you to replace a mod that was fine costs you an evening. A requirement on the loader, the game or Java is never reported as a missing mod - those are not files in mods/. If you did not include your mods/ folder it says so rather than answering with less than you think. And it does not write anything: it reads your folder and tells you what to change.

Want this on a real server? Supercraft hosts Minecraft →

Frequently asked questions

Is my server folder uploaded?

No. The whole diagnosis runs in this tab: the log is read locally, and each mod jar is opened locally just far enough to read its metadata file. Nothing is sent to us or anyone else. You can confirm it in your browser's network tab.

Why drop the whole folder instead of just the log?

Because the log alone cannot answer the question. The log says a class threw. The mods folder says which jar owns that class. That jar's own metadata says which version of which dependency it required, and the folder says which version is installed. Only together do those become 'replace flywheel-0.6.9.jar with 0.6.10'. A log analyzer that sees one file can only ever tell you the exception.

What does it actually read?

logs/latest.log and older logs, crash-reports, hs_err JVM crash files, every jar in mods/, config files, server.properties, user_jvm_args.txt and Spark reports. It picks the log covering the most recent failure rather than whichever file is first.

Will it change my server?

No. It only reads. Nothing is written, moved or deleted, and nothing leaves your browser. Corrected-pack generation is built and tested but not yet exposed here, so today the Doctor tells you what to change and you make the change.

Does it work when the server was killed by the host?

Yes, and that case is why whole-folder reading matters. A host out-of-memory kill leaves no exception and no crash report at all, so a rule-matching analyzer has nothing to match. The Doctor sees a run that reached the world and then simply stopped, and says so instead of sending you to audit your mods.

This tool: v1.6 · updated 20 Oct 2026