One launcher installs the client and its art packs, and keeps them current. Point it at your Ultima Online install once, add a shard, and play.
Built on the ClassicUO codebase around an ECS renderer. Windows will warn about an unknown publisher the first time — here is what to click.
Four steps. A few minutes of downloading on a normal connection, then you are in.
One 71 MB file. Save it anywhere — Desktop, Downloads, a USB stick. Nothing gets installed system-wide.
The launcher asks where the game should live and streams the files in. About 1.4 GB comes down the wire, about 9.3 GB ends up on disk.
Choose the folder where Ultima Online is installed. The client reads gumps, sounds, maps and tiledata from there, and will not start without tiledata.mul in it.
Enter the shard address you were given (host + port) and press Play. Next time, the launcher updates only the files that changed.
A modern client and a launcher that stays out of your way.
Files are compressed and fetched several at a time, so a fresh install takes minutes instead of an hour.
Every file is checked against its checksum as it lands, and a bad transfer is caught and named instead of quietly breaking your install.
When you open the launcher it compares what you have against the server and only pulls what changed.
Nothing is hard-coded to a single server. Keep several shards in the list and switch between them.
This build runs on an ECS renderer, so terrain and art are streamed in ahead of you rather than loaded in visible chunks as you move.
Gumps, sounds, maps and tiledata still come from an Ultima Online install. The launcher points the client at that folder, so you keep using the copy you already have.
Windows will be suspicious. Here is why, and what to click.
The launcher is not code-signed (that is a paid certificate), so SmartScreen shows a blue warning the first time you run it.
Some antivirus tools may also flag it and quietly move the file. If the launcher disappears after downloading, check your AV quarantine and allow it, then run it again.
Only the launcher and the folder you choose are touched. Nothing is installed into Program Files and no services are added.
The usual suspects, in the order they happen.
The client checks the path before it starts: the folder must contain tiledata.mul (or tiledata/tiledata.json), and the version has to come from client.exe or the launcher's version field.
That is the launcher failing to fetch the file list. Check your connection, then hit retry — it remembers what it already downloaded.
Almost always antivirus interfering mid-download. Exclude the game folder (and the launcher) in your AV, then retry.
Open the Logs folder next to MecsClient.exe and send the newest *_client.txt file — it names the actual failure.
Stuck? Ask in Discord — paste the log file and someone will read it.
Download the launcher, point it at your UO install, and the rest handles itself.
Windows 10/11 64-bit · no runtime needed · updates automatically