Pilot, You Are Cleared for Launch.
preFlight is an advanced 3D printing slicer. Building on the Slic3r legacy as a "spiritual successor" to PrusaSlicer, it offers exclusive features and a comprehensive under-the-hood overhaul, bringing the entire dependency stack up to modern standards. Switching is easy: preFlight natively imports PrusaSlicer and OrcaSlicer profiles so you can be up and running in minutes. To put it mildly, this is no ordinary fork.
Flagship Engineering
Athena Perimeter Generator
Something familiar, but completely different. Fixed extrusion widths with independent overlap control. Negative values create gaps for flexible materials.
Interlocking Perimeters
5-15% estimated Z-strength increase. Oversized beads compress into the interlocking pattern on the layer below. Fundamentally different from "brick layers."
Modern Stack
True 64-bit architecture, C++20, Clipper2, and a fully modernized dependency stack. Features built upstream, not bolted on. Roughly 50% less RAM usage.
G-code Preprocessing
Embedded Python scripting with 150 APIs. Per-move access to feedrate, flow, acceleration, junction angle, and region geometry. Bundled Python 3.14 runtime.
Export to Script
Hand your G-code to a Python script at export. Save to disk, upload via FTP, send to any networked printer, or all three at once. No proprietary API, just standard Python.
OrcaSlicer Import
PrusaSlicer profiles import natively. OrcaSlicer profiles go through a 230+ setting mapping engine with value transforms, G-code macro translation, and inheritance resolution.
Nip & Tuck Seams
V-shaped channel that absorbs start/stop blobs. Painted seam alignment with bidirectional blending and 0.1mm brush precision.
2-opt Travel Optimization
Region-aware infill ordering reduces travel distance 30–50%. Centroid-based starting position with full path optimization.
Maximum Commands Per Second
Diagnose printer stuttering at high speeds. See exactly how many G-code segments per second your settings generate per feature type.
Preview Clipping Plane
See inside your sliced objects with a cross-sectional clipping view. Right-click any object in the Preview to clip.
Paint-on Multi-Type Supports
Paint different support types (Snug, Grid, Organic) on different areas of the same object. Strong supports where you need them, easy removal everywhere else.
Counterbore Bridge Gizmo
Per-hole bridge layer control with smart fill. Fill direction adapts to each hole's corridor angle independently for optimal bridging.
CMYK+W Color Mixing
Multi-filament color blending using Beer-Lambert transmission physics. Paint any achievable color directly onto your model with up to 512 palette entries.
Align to Face Gizmo
Precisely position objects against any face of another model. Click a face, place an object, and combine with boolean operations for clean results.
Relief Gizmo
Emboss images as 3D heightmaps onto mesh surfaces. Real-time CSG preview with smoothing, gamma correction, and minimum thickness controls.
Mission Critical
Easy Switching
Natively imports PrusaSlicer profiles. OrcaSlicer bundle import translates 230+ settings, converts values, and maps G-code macros. A detailed report shows what transferred, what was converted, and what needs manual review.
Every Platform
Windows x64 and native ARM64. macOS on Apple Silicon, signed and notarized. Linux via AppImage. Raspberry Pi 5 via .deb. Same features, same codebase, every platform.
Works With Any Printer
Compatible with any modern 3D printer running RepRap-flavored G-code. STL, OBJ, 3MF, AMF, and STEP file support.
Free and Open Source
Licensed under GNU AGPL v3. We could have made this only valuable to our own customers. We didn't. This is us giving back to a community we've been part of for over 10 years.
Security First
All Windows binaries digitally signed. macOS notarized by Apple. 3MF post-process scripts suppressed on import. In-memory extraction prevents Zip Slip.
Active Development
We use preFlight daily and ship improvements constantly. Check the commit history and issue tracker - they speak for themselves.
Your Workspace, Your Way
Accordion or tabbed layouts with per-setting visibility. Toggle any setting on or off. Pinned preset selectors with quick-access print settings, printer, nozzle diameter, and filament controls. Show only what you use.
Physics-Based Time Estimation
Accurate print time predictions using real physics, not rough estimates. For RepRapFirmware users, settings are retrieved directly from your connected printer. Real-world compensation lets you dial in the algorithm to your specific machine.
Tuned for Your Hardware
Cap slicing threads, prefer P-cores on Intel hybrid processors, tune lighting quality, anti-aliasing, and preview detail for your GPU. Includes a fix for NVIDIA's threaded optimization conflict.
Ready to Strap In? You Have a Go for Download.
Free and open source under the GNU AGPL v3. Building on the Slic3r legacy with a modern C++20 foundation.