COMSOL is proprietary commercial software. There has never been an official "freeware" version. Any "free download" found on third-party file-sharing sites often involves cracked software, which poses significant security risks (malware/viruses) and is illegal.
Would you like help getting started with any of those free, legitimate alternatives? Comsol Multiphysics 3.5a Free Download
Detailed technical information on the software’s underlying mechanics and command structures is available in the Reference Guide . COMSOL is proprietary commercial software
If you are searching for this version for research or study, you may have legal avenues through an institution: Would you like help getting started with any
Before downloading COMSOL Multiphysics 3.5a, ensure that your computer meets the minimum system requirements:
Released in the late 2000s (around 2008), COMSOL 3.5a represented a significant step in the evolution of the software. It was built upon the acquisition of FEMLab by COMSOL and was instrumental in popularizing the concept of "Multiphysics"—the ability to couple different physical simulations (like structural mechanics and fluid dynamics) seamlessly in one environment.