When working with 3D models and CAD software, it's essential to have a reliable STP file viewer to open, inspect, and analyze your designs. Whether you're a professional engineer, designer, or hobbyist, there are several free STP file viewers available that can help you easily access and share your 3D models. Check out some of the best free STP file viewers below:

1. FreeCAD: FreeCAD is a powerful open-source parametric 3D CAD modeler. It supports the STP file format and offers a range of tools for designing and editing 3D models. With its intuitive interface and extensive features, FreeCAD is a popular choice for engineers and designers.

2. eDrawings Viewer: eDrawings Viewer is a free software from SOLIDWORKS that allows users to view and share 3D models in various file formats, including STP. It provides easy-to-use tools for measuring, marking up, and reviewing designs, making it suitable for collaboration and presentations.

3. Autodesk Viewer: Autodesk Viewer is a free online tool that supports viewing 2D and 3D designs, including STP files. It enables users to visualize and share designs without the need for specific software, making it convenient for project stakeholders to review and provide feedback.

4. A360 Viewer: A360 Viewer is a web-based tool by Autodesk that allows users to view, share, and collaborate on 2D and 3D designs, including STP files. It offers features for measuring, sectioning, and markup, making it a versatile choice for teams working on design projects.

5. Onshape: Onshape is a cloud-based CAD platform that offers a free plan for non-commercial use. With its built-in STP file viewer, users can access and edit 3D models from any device with an internet connection. Onshape also supports real-time collaboration and version control for seamless teamwork.

These free STP file viewers provide essential capabilities for opening, visualizing, and sharing 3D designs without the cost of premium software. Whether you're a professional engineer working on complex projects or a hobbyist exploring 3D modeling, these tools offer accessible solutions for viewing and collaborating on STP files.