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Opening Mainsail
Open your printer's web interface, called Mainsail, from a computer or phone on the same network. Mainsail is where uploading files and watching prints is easiest.
- A printer on your Wi-Fi network - see Connecting to Wi-Fi.
- A computer, tablet or phone on the same network.
Mainsail is a web page served by the printer itself. You do not install anything and you do not need an account or an internet connection - your browser talks directly to the printer over your own network.
The printer's touchscreen and Mainsail show the same printer and work at the same time. Neither replaces the other: the screen is better when you are standing at the machine, Mainsail is better for uploading files and watching from elsewhere in the house.
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On the printer, tap Settings → Connections and read the Address line. It looks like
192.168.1.42. -
On your computer or phone, open a web browser.
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Type that address into the address bar - the box where you would normally type a web address - and press Enter.
Type just the numbers and dots. Do not add
www.and do not search for it. -
Mainsail opens.
Read the Address line here. The printer's name is just above it, and Change renames it.
The printer also answers to its own name, so you do not have to remember numbers:
http://<printer-name>.local
The name is on Settings → Connections, next to Name, and Change renames it. After
a rename, the printer is reachable at the new .local address.
Each printer gets its own name by default. NebulaOS names a new printer
nebulaos- followed by four characters derived from its own hardware, for example
nebulaos-4f2a. That is deliberate: if every printer were simply called nebulaos, two of
them on one network would collide in your router, in Mainsail and at nebulaos.local. A name
you choose yourself always wins over the default.
This naming trick works on most home networks, but not all - some routers and some Android
versions do not support it. If .local does not work for you, use the numeric address.
Mainsail opens and shows your printer's dashboard: temperatures, a file list, and controls. If the printer is idle, temperatures read roughly room temperature.
| What happens | What to do |
|---|---|
| The page does not load | Check the device is on the same Wi-Fi network, not a guest network or mobile data. |
| The address has changed | Your router may hand out a different address after a restart. Read it again on Settings → Connections, or set a fixed address. |
.local does not work but the numbers do |
Your network does not support .local names. Use the numeric address. |
| It loads but says it cannot reach the printer | Klipper may still be starting. Wait a minute and reload. |
| Nothing works and the screen is also dead | Troubleshooting, then Recovery. |
Save the address in your browser. If you set a fixed address (Connecting to Wi-Fi), the bookmark keeps working permanently; with DHCP it may occasionally change.
First-time setup - calibration and your first print.