MetaWin 3 is a free, open-source, multi-platform software for meta-analysis, developed in Python. It replaces earlier versions, which were written in Pascal and Delphi and relied on commercial licenses, limiting their availability. MetaWin 3 provides standardized effect size calculations, exploratory and publication bias analyses, and supports both simple and complex explanatory models, including meta-regression. It includes a user-friendly GUI, automated citations, and graphical outputs with auto-generated captions. The software is available on GitHub and offers pre-compiled versions for Windows and macOS. MetaWin 3 includes eight primary analytical methods, such as effect size calculations, publication bias exploration, and meta-analytic computation. It also allows for additional graphical outputs like funnel plots, forest plots, and Galbraith radial plots. The software is released under a GPL-3.0 license and is freely available for download. It is designed to be accessible to users with varying levels of expertise, offering a balance between ease of use and powerful analytical capabilities. The software is intended to fill the gap between MetaWin 2 and the R-based meta-analytic community, providing a more flexible and open-source alternative. MetaWin 3 is a significant advancement in meta-analysis software, offering improved functionality and accessibility for researchers in various fields.MetaWin 3 is a free, open-source, multi-platform software for meta-analysis, developed in Python. It replaces earlier versions, which were written in Pascal and Delphi and relied on commercial licenses, limiting their availability. MetaWin 3 provides standardized effect size calculations, exploratory and publication bias analyses, and supports both simple and complex explanatory models, including meta-regression. It includes a user-friendly GUI, automated citations, and graphical outputs with auto-generated captions. The software is available on GitHub and offers pre-compiled versions for Windows and macOS. MetaWin 3 includes eight primary analytical methods, such as effect size calculations, publication bias exploration, and meta-analytic computation. It also allows for additional graphical outputs like funnel plots, forest plots, and Galbraith radial plots. The software is released under a GPL-3.0 license and is freely available for download. It is designed to be accessible to users with varying levels of expertise, offering a balance between ease of use and powerful analytical capabilities. The software is intended to fill the gap between MetaWin 2 and the R-based meta-analytic community, providing a more flexible and open-source alternative. MetaWin 3 is a significant advancement in meta-analysis software, offering improved functionality and accessibility for researchers in various fields.