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GRBL Server
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Installation

GRBL Server runs as a Windows desktop application that hosts a small web server on your local network. You install it on one computer per workshop — the host. Everyone else (phones, tablets, laptops) reaches the UI through a browser on the same Wi-Fi.

This page walks you through getting from the download link to a running server that other devices can reach.

Requirements

  • Host computer: Windows 10 or 11, 64-bit. At least 2 GB of free RAM.
  • Network: the host must be on the same Wi-Fi (or wired LAN) as any device you want to control it from.
  • Hardware: USB ports for serial controllers, or network reach for Wi-Fi (ESP32) and TCP controllers.
  • Browser (on client devices): a modern browser. Chrome, Edge, Firefox, and Safari are all fine.

Install steps

  1. Download the latest installer from the download page.
  2. Run the installer. It's digitally signed, so the Windows User Account Control prompt shows the verified publisher SISTEMAS TECNICOS CATALUNYA S.L — confirm to continue. On a brand-new build, SmartScreen may still show a "Windows protected your PC" notice while the fresh signature builds reputation; if it does, click More info, then Run anyway.
  3. Choose an install location (the default is fine). The installer creates a Start menu entry and a desktop shortcut.
  4. After install, launch GRBL Server from the Start menu.
  5. A small launcher window appears showing the address to open in a browser — the host's IP (for example http://192.168.1.42) and a grblserver.local shortcut.
  6. Type the IP address into a browser on any device on the same network. The GRBL Server UI loads.

First launch checklist

The first time you open the UI in a browser, three things should happen in order:

  1. You land on the Sign in page. Use the account you created on the GRBL Server website. See Login & accounts for the full flow.
  2. After signing in, the sidebar loads with Working, File Loaders, Configuration, Storage and Software Settings groups.
  3. A small launcher window stays open on the host computer. You can minimise it but don't close it — closing the launcher stops the server.

Firewall & private network

On first launch, Windows usually shows a firewall prompt asking whether to allow GRBL Server to communicate.

  • ✅ Allow it on Private networks so other devices on your Wi-Fi can reach the UI.
  • ❌ You don't need to allow Public networks. GRBL Server is meant to be reached only from inside your local network.

GRBL Server also tries to add a small firewall rule for the grblserver.local shortcut (mDNS, UDP 5353). Creating that rule needs administrator rights — running GRBL Server as administrator once lets it add the rule for every network profile. This is optional: the IP address works whether or not the rule exists.

Accessing the UI from other devices

The launcher window shows two ways to reach the server. Open either one in a browser on any device on the same Wi-Fi.

By IP address — recommended

Type the host's address exactly as the launcher shows it:

http://192.168.1.42

Replace 192.168.1.42 with your host's IP. Most of the time that's the whole address — but if the launcher shows a port after the IP, include it too (see Port selection below). The IP address works on every device, so this is the method to rely on.

By name — grblserver.local

So you don't have to memorise an IP, the server also answers to a fixed name:

http://grblserver.local

As with the IP, that's usually the whole address — add a port only if the launcher shows one after it.

It's the same UI whether you open it on the host or on a phone — you're not running anything on the client device, just a browser tab.

Port selection

You normally never have to think about the port. By default GRBL Server picks one itself at startup, so it works out of the box even when other software on the host already occupies common ports. It tries these in order and takes the first that is free:

  1. 80 — the standard web port; when this one is used, the address needs no :port suffix at all.
  2. then 5000, 8080, 8000, 8888.
  3. if every one of those is busy, a random free port chosen by Windows.

Whichever it lands on, the launcher window shows the full address, and the grblserver.local shortcut always points at the same port.

Pinning a fixed port

If you need the server on a predictable port — for a bookmark, a firewall rule, or a router port-forward — you can pin one:

  1. Open Software Settings → Settings in the GRBL Server UI and select the APP section.
  2. On the port row, switch the toggle from Automatic to Manual and type the port you want.
  3. Save, then restart GRBL Server. The launcher shows the new port.

Updating to a new beta build

Beta updates aren't automatic yet. To update:

  1. Close the launcher window on the host (right-click the tray icon → Quit).
  2. Download the new installer from the download page.
  3. Run the installer. It upgrades the existing installation in place — your machines, presets, workflows, and jobs are preserved.

Uninstalling

Remove GRBL Server through Windows Settings → Apps → Installed apps → GRBL Server → Uninstall. The uninstaller removes the application but keeps your data folder so you don't lose your setup if you reinstall later.

What's next

Something unclear or wrong on this page? Tell me — beta docs improve fastest from real questions.