Free online viewers for CAD and 3D formats

1)  Autodesk Viewer
Easily view and share designs in your browser.
Autodesk Viewer makes it easy to share views of your designs and collaborate remotely.
Supported most 2D and 3D files:
including DWG, STEP, DWF, RVT and Solidworks (3DM 3DS A ASM AXM BRD CATPART CATPRODUCT CGR COLLABORATION DAE DDX DDZ DGK DGN DLV3 DMT DWF DWFX DWG * DWT DXF EMODEL EXP F3D FBRD FBX FSCH G GBXML GLB GLTF IAM IDW IFC IGE IGES IGS IPT IWM JT MAX MODEL MPF MSR NEU NWC NWD OBJ OSB PAR PMLPRJ PMLPRJZ PRT PSM PSMODEL RCC RCS RVM RVT ** SAB SAT SCH SESSION SKP SLDASM SLDPRT SMB SMT STE STEP STL STLA STLB STP STPZ VPB VUE WIRE X_B X_T XAS XPR)

https://viewer.autodesk.com/

2) ShareCAD
Supported CAD formats: AutoCAD® DWG, DXF, DWF, HPGL, PLT
Supported 3D formats: STEP, STP, IGES, IGS, BREP, STL, SAT (ACIS), Parasolid® (X_T, X_B), SolidWorks® (SLDPRT), IPT, IFC, OBJ

https://beta.sharecad.org/

3) DWG FastView

View CAD drawings online
Open your CAD drawings in all major browsers with the latest DWG FastView online version, no installation or upgrade needed.
Supported CAD formats: *.ocf;*.dwq;*.dxf;*.dws;*.dwt

https://en.dwgfastview.com/