The OSGeo4W installer is recommended for regular users or organization deployments. It allows to have several QGIS versions in one place, and to keep each component up-to-date individually without having to download the whole package.
QGIS requires Windows 8 64 bit or higher because QGIS uses Python 3.9 or later, which is not available for Windows 7.
macOS High Sierra (10.13) or newer is required. QGIS is not yet notarized as required by macOS Catalina (10.15) security rules. On first launch, please right-click on the QGIS app icon, hold down the Option key, then choose Open.
The QGIS experience does not stop on the desktop. Various touch optimized apps allow you to take QGIS into the field
Third-party touch optimized apps
QGIS for Android
An old and deprecated not touch optimised release of QGIS for Android can be found inAll downloads
More specific instructions about downloading QGIS stable vs QGIS development can be found in All downloads.
For testing and learning purposes, a sample dataset is available, which contains collections of data from different sources and in different formats.
Plugins for QGIS are also available here.
QGIS is open source software available under the terms of the GNU General Public License meaning that its source code can be downloaded through tarballs or the git repository.
Refer to the INSTALL guide on how to compile QGIS from source for the different platforms: here