Third-party sites frequently offer "Civil 3D Portable 2024" or similar downloads. Using these unofficial versions carries heavy risks: Does Civil 3D include AutoCAD features - Autodesk
Even if a portable version could be hacked to run, USB 3.0/3.1 speeds (max ~400 MB/s) are far slower than NVMe SSDs (3,500+ MB/s). Opening a 200 MB corridor model would be unusable. civil 3d portable