Neither program is firmware or a slicer. Klipper runs the printer, Moonraker exposes a web API that client applications use, and Mainsail or Fluidd is the browser interface on top. Klipper's installation guide describes Fluidd and Mainsail as the two main Moonraker-based front ends.
Because both sit on the same API, the choice is mostly about layout, installation route and the specific features each project documents.
Mainsail and Fluidd side by side
| Feature | Mainsail | Fluidd |
|---|---|---|
| Maintainers | Maintained by meteyou with community contributors | Built by volunteers in the fluidd-core organization |
| License | GPL-3.0 | GPL-3.0 |
| Price | Free and open source | Free and open source |
| Requires | Klipper and Moonraker | Klipper and Moonraker |
| Latest version | 2.19.0, released August 27, 2026 | 1.37.7, released October 16, 2026 |
| Install options | MainsailOS image, KIAUH, Docker, manual setup, hosted my.mainsail.xyz | KIAUH, manual setup, release download, Docker image |
| Prebuilt OS image | MainsailOS for Raspberry Pi and some Orange Pi boards | Not verified |
| Devices | Desktop, tablet and mobile browsers | Desktop, tablet and mobile browsers |
| Multiple printers | Yes (printer farm) | Yes, from one install |
| Webcams | Multiple webcams; timelapse via moonraker-timelapse | Multiple webcams (MJPEG, HLS, WebRTC) |
| Other documented features | Job queue, print history, object exclusion, power devices, macro prompts, themes and custom CSS | Spoolman spool management, diagnostics dashboard, file editor, Obico and OctoEverywhere integrations |
Checked November 2, 2026 against Mainsail 2.19.0 (released August 27, 2026) and Fluidd 1.37.7 (released October 16, 2026), the latest releases on each GitHub release page.
How they fit into a Klipper setup
Klipper's documentation says its front ends retrieve information through the Moonraker web API. Moonraker's own documentation describes it as a Python 3 web server that exposes APIs for client applications and talks to Klipper's host process. Mainsail and Fluidd are two such clients, so neither works on a printer that is not running Klipper and Moonraker.
Both projects are GPL-3.0 and free. Mainsail's documentation says it is maintained by meteyou with community contributors and lists hardware vendors that support it financially. Fluidd describes itself as built by volunteers and credits Klipper, Moonraker, KIAUH and MainsailOS developers.
Installation routes
Mainsail documents several routes: the MainsailOS image, the KIAUH installer, Docker, manual setup and a hosted copy of the interface at my.mainsail.xyz that connects to your own printers. Klipper's guide notes that MainsailOS supports Raspberry Pi and some Orange Pi boards.
Fluidd's README recommends KIAUH, which can also install Klipper and Moonraker, and offers manual setup, release downloads and an official Docker image that serves the interface on port 80, or 8080 for the unprivileged image.
Features compared
The core lists overlap: live status and temperatures, file upload and in-browser editing, macros, bed-mesh visualization, a G-code viewer, print history, webcams and multi-printer control. Both describe responsive layouts for desktop, tablet and phone screens, customizable dashboards and themes.
Differences are in the details each project chooses to highlight. Mainsail lists a job queue, object exclusion during prints, smart power device control and timelapses through moonraker-timelapse. Fluidd lists Spoolman spool tracking, MJPEG, HLS and WebRTC webcam streams, a diagnostics dashboard and integrations such as Obico and OctoEverywhere. Its 1.37.7 release added CSV export for print history.
Recent releases
Both projects ship small, frequent updates. Fluidd 1.37.7, released October 16, 2026, added grouped console prompt buttons, CSV export of print history, display of Klipper and Kalico MCU build settings, and lazy loading of file thumbnails. Mainsail 2.19.0, released August 27, 2026, added two add-on log files to its log panel. Fluidd's documentation also lists automated updates for Klipper, Moonraker and Fluidd from inside the interface.
Which should you choose?
Choose Mainsail if…
- You want to flash a ready-made MainsailOS image to a Raspberry Pi or supported Orange Pi.
- You want a print job queue and object exclusion listed among the core features.
- You want a hosted interface at my.mainsail.xyz that connects to printers on your network.
Choose Fluidd if…
- You track spools with Spoolman and want it in the dashboard.
- You use HLS or WebRTC webcam streams, which Fluidd lists alongside MJPEG.
- You want built-in hooks for Obico or OctoEverywhere.
Common questions
Can I run Mainsail or Fluidd without Klipper?
No. Both are front ends for Klipper that communicate through the Moonraker API, so the printer must run Klipper with Moonraker.
Can I install both and switch?
Both use the same Moonraker API, and installers such as KIAUH can set up either one. Back up your configuration before changing your setup.
Is either one a slicer?
No. You still prepare G-code in a slicer, then upload and run the job through the interface.
Sources
- Mainsail documentation Mainsail project · Checked 2026-11-02
- Fluidd documentation Fluidd project · Checked 2026-11-02
- Fluidd repository and README Fluidd project on GitHub · Checked 2026-11-02
- Mainsail repository and README Mainsail project on GitHub · Checked 2026-11-02
- Klipper installation guide (front ends) Klipper project · Checked 2026-11-02
- Mainsail v2.19.0 release notes Mainsail project on GitHub · Checked 2026-11-02
- Fluidd v1.37.7 release notes Fluidd project on GitHub · Checked 2026-11-02
- Moonraker documentation Moonraker project · Checked 2026-11-02
This comparison summarizes the cited documentation; it is not a lab test. Features and prices change between releases; check the developer’s site for the current version.