LightBurn Not Detecting Laser — 7 Fixes That Actually Work

How LightBurn Finds Your Laser

When you plug in a laser engraver via USB, the machine's controller presents itself to your computer as a virtual serial (COM) port. LightBurn connects to that COM port using settings you configure — device type, baud rate, and port number. If any of those three things are wrong, or if the COM port never appeared in the first place, LightBurn will fail to detect or connect to the machine.

There are two distinct failure modes. Not found at all means no COM port appeared — a hardware or driver problem. Found but won't connect means the COM port appeared but LightBurn can't talk to the machine — usually a wrong device type or baud rate. The fixes are different for each.

Start with Step 1 and work forward. Each step takes under two minutes. Most users find the cause by Step 4.

Step 1: Check the USB Cable and Port

This is the single most-overlooked cause and the fastest to test. Many USB cables — especially the short ones bundled with laser machines — are charge-only. A charge-only cable has no data wires, so your computer cannot see the laser at all regardless of software or driver status.

Test: Swap in a USB cable you know carries data (the one from a phone that you've used to transfer files works). Also try a different USB port on your computer — switch from a front panel port to a port directly on the motherboard (rear ports on a desktop, or a different port on a laptop). Avoid USB hubs for troubleshooting; connect directly.

If the cable swap fixes it: Replace the bundled cable. The laser manufacturer's cable is frequently the problem for machines sourced from overseas.

USB 3.0 compatibility note: Some older CH340 USB chips have intermittent compatibility issues with USB 3.0 ports. If your laser works on some ports but not others, try a USB 2.0 port (often labeled with a black connector vs. the blue of USB 3.0). A USB 2.0 hub inserted between the machine and a USB 3.0 port can also resolve this.

Step 2: Install or Reinstall the USB Driver

Laser engraver controllers use USB-to-serial bridge chips to present themselves as COM ports. The two most common are the CH340 (used by most Chinese diode laser brands) and the CP2102 (used by some xTool and Sculpfun machines). These chips require drivers that Windows does not include by default — or includes an older version that sometimes stops working after OS updates.

How to check if the driver is missing: Open Device Manager (right-click Start → Device Manager on Windows). Expand "Ports (COM & LPT)". If your laser is listed there when plugged in, the driver is working. If you see an "Unknown Device" with a yellow triangle anywhere in the list, the driver is not installed correctly.

CH340 driver download: Search for "CH340 driver WCH" and download from the official WCH website (wch.cn or wch-ic.com). Install, unplug and replug the laser, and check Device Manager again.

CP2102 driver download: Search for "CP2102 driver Silicon Labs" and download from silabs.com. Same install process.

On Mac: CH340 drivers are not included in macOS. Download from the WCH site or use the Homebrew formula brew install wch-ch34x-usb-serial-driver. After installing, go to System Settings → Privacy & Security and approve the kernel extension. Reboot, then reconnect the laser.

Step 3: Verify the Device Type in LightBurn

Even if the laser appears as a COM port, LightBurn must be configured with the correct device protocol. Using the wrong device type causes LightBurn to send commands the controller does not understand, resulting in connection failure or a machine that receives no response.

Common device types:

• GRBL — Used by most diode lasers: Sculpfun, Atomstack, Ortur, Aufero, older xTool D1 models, Two Trees, and many others.
• xTool (specific profile) — Newer xTool machines (D1 Pro 2, S1, F1, P2) use an xTool-specific protocol. Select the xTool device type in LightBurn, not GRBL.
• Ruida — Standard protocol for Chinese CO2 laser cutters (OMTech, Thunder, Boss, etc.).
• Trocen/AWC — Used by some mid-range CO2 machines.
• Marlin — Uncommon in dedicated laser machines but used in some 3D-printer-converted setups.

To change device type in LightBurn: go to Edit → Devices, select your device, click Edit, and verify or change the device type. If unsure, check your machine's manufacturer documentation or the LightBurn device database on their website.

Step 4: Select the Correct COM Port

LightBurn stores a specific COM port in each device's settings. If you plugged the laser into a different USB port than before, or if Windows reassigned the port number after an update, the stored port number is now wrong.

Find the current port number on Windows: Device Manager → Ports (COM & LPT). With the laser plugged in, your device will appear as something like "USB-SERIAL CH340 (COM5)". The number in parentheses is the port you need.

Update in LightBurn: Edit → Devices → select your device → Edit. In the connection settings, change the COM port to match what Device Manager shows. Click OK and attempt to connect.

Pro tip: In Windows Device Manager, you can right-click the COM port entry and set a fixed port number under Properties → Port Settings → Advanced → COM Port Number. Assigning a fixed port (e.g., COM3) means LightBurn's settings will always be correct regardless of which USB port you use, as long as the same USB hub/port path is maintained.

Step 5: Close Competing Software

Only one application can hold a COM port at a time. If the manufacturer's app is running in the background — xTool Creative Space, LaserGRBL, Candle, or any other controller — it may have already claimed the COM port, leaving LightBurn unable to connect.

Fix: Close all laser-related applications. If you're unsure what's running, use Task Manager (Windows) or Activity Monitor (Mac) to check. Also check for background processes — some apps continue running in the system tray after their window is closed.

This is a particularly common issue when users switch from the manufacturer's bundled software to LightBurn. The old software may launch at startup and claim the port before LightBurn opens. Disable the startup launch in the old app's settings.

Step 6: Power the Laser Before Opening LightBurn

Some laser controllers go through a boot sequence after power-on and are not ready to accept a connection for several seconds. If LightBurn opens before the laser finishes booting, the connection attempt fails and LightBurn may mark the device as unavailable for the rest of the session.

Correct sequence:

1. Power on the laser.
2. Wait 10–15 seconds for the controller to boot.
3. Plug in the USB cable (or confirm it's already connected).
4. Open LightBurn.
5. Click "Connect" or check the connection status in the bottom left of the LightBurn window.

If LightBurn is already open when you power on the laser, go to Edit → Devices, select your device, and click "OK" to re-trigger the connection attempt after the laser has finished booting.

Step 7: Re-run Find My Laser

If the steps above haven't resolved the issue, use LightBurn's built-in device scanner to find your laser fresh.

Go to Edit → Devices → Find My Laser (or the "+" button → Find My Laser in some versions). LightBurn will scan all available COM ports and attempt to identify connected devices. If it finds your laser, it will show the device type and port. Click "Next" to add it as a new device.

If you had a previously configured device for the same machine, delete the old entry first to avoid duplicates. The new entry from the scan will have the correct current port and protocol.

If Find My Laser finds nothing: The problem is at the driver or hardware level, not LightBurn configuration. Return to Steps 1–2 and confirm the laser appears in Device Manager with no warning icons before attempting LightBurn connection again.

COM Port and Driver Quick-Reference Table

Note: Glowforge machines connect only through Glowforge's own cloud app and are not compatible with LightBurn. See our Glowforge vs xTool comparison for more on this difference.