Fifteen years to the day after developer @alranel made the first commit to Slic3r — the open-source slicer that would eventually become PrusaSlicer — on September 1, 2011, Prusa Research released an alpha preview of a version that shares little more than a name with its predecessor. Announced on the company blog on September 1, 2026, PrusaSlicer 3.0-preview is, in the company's own words, "the biggest upgrade in PrusaSlicer's history" — and after reading through the feature list, it's hard to argue otherwise.
This isn't a point release with a new icon set bolted onto the old engine. It's a rewrite of the interface, the profile system, and the plugin architecture, released deliberately early and incomplete so the community can watch it take shape.
A Slicer Built for Machines That Don't Exist Yet
The headline change is the project system. Where every version of PrusaSlicer since its Slic3r roots has worked around the concept of a single bed with a single printer profile, 3.0 tears that assumption out. A project can now hold an unlimited number of beds, each tied to a different printer — up from a hard cap of nine in the 2.9.x line — and those beds can be sliced in parallel rather than one at a time. For anyone running a print farm with mismatched machines, that's a structural change, not a convenience feature. The profile format underneath it all has changed too. PrusaSlicer has used INI-style .ini files for its printer, filament, and print profiles since the Slic3r era. 3.0 replaces them with YAML, a format designed around modern multi-tool printers that lets a project select a nozzle per tool without needing a separate printer profile for every combination. It's a foundation-level change that will require conversion tooling for anyone with a library of custom profiles built up over a decade of tuning — Prusa hasn't detailed a migration path yet. Existing 3MF project files from PrusaSlicer 2.x do load correctly in the new version, so the break is in the standalone profile library, not in projects people already have open.
New Interface, New Navigation, New Plugin Model
The UI has been redesigned wholesale: tool icons move to the top of the window, a collapsible scene browser sits on the left for managing multi-object and multi-bed projects, and a contextual panel on the right adapts to whatever is selected. A View Cube — the kind of 3D orientation widget CAD users will recognize from Fusion 360 or SolidWorks — makes its first appearance in PrusaSlicer, alongside a new light theme (dark remains the default) and a choice of navigation schemes modeled on Tinkercad, Blender, SolidWorks, and Fusion — a signal Prusa is chasing users who already live in a CAD package. The rendering pipeline has also gained more advanced OpenGL handling — shadows, reflections, and ambient occlusion, with toolpaths hidden during rotation and rendered on pause — which should pay off in viewport performance on complex, multi-bed scenes. Underneath the UI, PrusaSlicer gains a scripting layer for the first time: a sandboxed Lua plugin system with no access to disk, outside-project data, or the network. It ships with built-in calibration prints — a flow tower and a temperature tower — implemented as Lua plugins rather than hardcoded features, and Prusa has stated a community plugin marketplace with a review process is planned for an upcoming release. The company is explicit that the Lua API is not stable yet and is subject to breaking changes during development, so plugin authors should treat anything built against the preview as disposable for now.
Small but Meaningful: Auto-Recovery and Offline Mode
Two additions are easy to overlook next to the interface overhaul but matter for daily use. Auto-recovery backups, saved continuously to a backup_projects folder in the PrusaSlicer data directory, solve the familiar pain of losing plate arrangement and support painting to a crash or an accidental quit. And PrusaSlicer 3.0 introduces a genuine offline mode: no networking libraries are loaded at all when it's enabled, which will appeal to users on air-gapped machines, in secure facilities, or who simply don't want a slicer phoning home. The AGPLv3 license that has governed PrusaSlicer since it forked from Slic3r remains unchanged, so the source obligations and copyleft terms makers are used to still apply.
What It Means for Makers
The most important caveat sits at the top of Prusa's own announcement: this preview supports Prusa printers only. Third-party printer support — which the current 2.9.x line handles reasonably well through community and vendor profiles — is simply absent from this preview, and Prusa has not published a timeline for adding it. If you run a Voron, a Bambu machine, or anything outside Prusa's own catalog, there is nothing to do here yet except watch. Even Prusa owners should treat this as exactly what it's labeled: a feature-incomplete alpha, not "polished, nearly-ready," and not a replacement for the 2.9.x line on a deadline print. Prusa has said some features won't be fully reimplemented until version 3.1.0, so the rough edges here won't fully smooth out even once 3.0 itself ships. The value right now is visibility — Prusa is showing its hand early enough that the community can weigh in on the YAML profile schema, the Lua API surface, and the new UI's navigation schemes while they're still being shaped. Independent trade coverage from VoxelMatters, which covered the release the same day under the headline "Prusa Research makes major upgrades with new PrusaSlicer 3.0" — noting it lands mere weeks after Prusa refreshed its printer lineup, and quoting Prusa's own description of it as "a big one" — treats it with the same framing: significant, but a preview, not a shipped product. For makers with print farms mixing multiple printer models, the unlimited multi-bed project system is worth tracking closely — it addresses a real limitation of the current software. For anyone running multi-tool or multi-material setups, the YAML profile overhaul is aimed squarely at you, though it also means budgeting time to migrate custom profiles once a conversion path exists. And for the plugin-curious, the Lua sandbox with its planned marketplace is the first real extensibility path PrusaSlicer has offered — worth experimenting with, but not worth depending on until the API stabilizes.
The practical takeaway: install the preview alongside your existing 2.9.x installation, expect it to be Prusa-only and rough around the edges, and don't move a production workflow onto it yet. Prusa's own download page — linked from the announcement — makes the alpha available now for anyone who wants to kick the tires ahead of a fuller release.
