OSGeo · ecodiv · May 10, 2026 · May 10, 2026 · May 10, 2026 · May 14, 2026
diff --git a/scripts/g.extension/g.extension.html b/scripts/g.extension/g.extension.html
@@ -126,6 +126,49 @@ <h3>Compilation and installation</h3>
 as manual page are compiled, not only the source code (which is really
 necessary to compile just in case of C).
 
+<h3>Using an alternative addon server (MS-Windows)</h3>
+
+On MS-Windows, <em>g.extension</em> downloads precompiled addon ZIPs from the
+official WinGRASS server (<code>http://wingrass.fsv.cvut.cz</code>) by default.
+The base URL of the server can be redirected to a mirror or a private addon
+server by setting <code>ADDONS_BASE_URL</code>. The setting affects both the
+addon listing (<code>g.extension -l</code>, <code>-c</code>, <code>-g</code>)
+and the install download URL, so listing and install always come from the same
+place.
+
+<p>
+The setting can be applied in two ways:
+
+<ul>
+<li>From inside GRASS (persists across sessions, settable from the GUI's
+    variables panel as well):
+<div class="code"><pre>
+g.gisenv set="ADDONS_BASE_URL=https://your.server.example"
+</pre></div>
+</li>
+<li>As a shell environment variable named <code>GRASS_ADDONS_BASE_URL</code> (useful
+    for one-off shell sessions or CI jobs). The gisenv setting takes
+    precedence over the environment variable; if neither is set, the
+    default WinGRASS server is used.</li>
+</ul>
+
+<p>
+To revert to the default server, unset the value:
+
+<div class="code"><pre>
+g.gisenv unset=ADDONS_BASE_URL
+</pre></div>
+
+<p>
+Alternative servers are:
+<ul>
+<li><a href="https://ecodiv.earth/share">https://ecodiv.earth/share</a> (Python extensions only)</li>
+</ul>
+
+<p>
+Note, settings explained in this section are is honoured on MS-Windows only; on
+Linux/macOS it has no effect.
+
 <h2>EXAMPLES</h2>
 
 <h3>Download and install of an extension</h3>
@@ -143,6 +186,35 @@ <h3>Download and install of an extension</h3>
 g.extension r.stream.distance
 </pre></div>
 
+<h3>Installing from an alternative addon server (MS-Windows)</h3>
+
+On MS-Windows, redirect the addon server to a mirror or private host
+once per session, then use <em>g.extension</em> normally — listing and install
+both go through the configured server.
+
+<div class="code"><pre>
+# Point at the alternative server (persists across GRASS sessions)
+g.gisenv set="ADDONS_BASE_URL=https://ecodiv.earth/share"
+
+# List what the alternative server provides
+g.extension -l
+
+# Install an extension from it
+g.extension extension=r.tpi
+
+# Revert to the default WinGRASS server
+g.gisenv unset=ADDONS_BASE_URL
+</pre></div>
+
+<p>
+For a one-off shell session, set the environment variable instead:
+
+<div class="code"><pre>
+# cmd.exe
+set GRASS_ADDONS_BASE_URL=https://ecodiv.earth/share
+g.extension extension=r.tpi
+</pre></div>
+
 <h3>Download and install of an extension when behind a proxy</h3>
 
 Example for an open http proxy:
@@ -204,8 +276,10 @@ <h3>Installing from various online repositories: GitHub, GitLab, Bitbucket</h3>
 g.extension r.example url=http://example.com/.../r.example?format=zip
 </pre></div>
 
-Note that because of MS-Windows operating system architecture,
-only official repository is supported on this platform.
+On Windows, this will work also, but only when pointing at a server with
+pre-compiled addons and set up using the same directory layout as the
+official WinGRASS server, namely <code>{base}/grass{MM}/addons/grass-{M.M.P}/</code>
+containing one ZIP per extension and a <code>modules.xml</code> listing.
 
 <h3>Install a specific version from Addons</h3>
 
@@ -248,6 +322,12 @@ <h2>KNOWN ISSUES</h2>
 <!-- what does it mean?? -->
 (a Python replacement for Python scripts should be implemented).
 
+<p>
+On Windows, it is now possible to point at an alternative server. However, note
+that this server should be set up using the same directory layout as the
+official WinGRASS server, namely <code>{base}/grass{MM}/addons/grass-{M.M.P}/</code>
+containing pre-compiled extensions as ZIP file, and a <code>modules.xml</code> listing.
+
 <h2>TROUBLESHOOTING</h2>
 
 Since extensions have to be compiled on Unix based systems (Linux, Mac OSX etc.)
@@ -276,4 +356,5 @@ <h2>AUTHORS</h2>
 
 Markus Neteler (original shell script)<br>
 Martin Landa, Czech Technical University in Prague, Czech Republic (Python rewrite)<br>
-Vaclav Petras, <a href="https://geospatial.ncsu.edu/geoforall/">NCSU GeoForAll Lab</a> (support for general sources, partial refactoring)
+Vaclav Petras, <a href="https://geospatial.ncsu.edu/geoforall/">NCSU GeoForAll Lab</a> (support for general sources, partial refactoring)<br>
+Paulo van Breugel, HAS green academy (add option for Windows users to point at alternative repositories)
diff --git a/scripts/g.extension/g.extension.md b/scripts/g.extension/g.extension.md
@@ -115,6 +115,42 @@ extensions. The reason is that more things such as manual page are
 compiled, not only the source code (which is really necessary to compile
 just in case of C).
 
+### Using an alternative addon server (MS-Windows)
+
+On MS-Windows, *g.extension* downloads precompiled addon ZIPs from the
+official WinGRASS server (`http://wingrass.fsv.cvut.cz`) by default.
+The base URL of the server can be redirected to a mirror or a private
+addon server by setting `ADDONS_BASE_URL`. The setting affects both the
+addon listing (`g.extension -l`, `-c`, `-g`) and the install download
+URL, so listing and install always come from the same place.
+
+The setting can be applied in two ways:
+
+- From inside GRASS (persists across sessions, settable from the GUI's
+  variables panel as well):
+
+  ```sh
+  g.gisenv set="ADDONS_BASE_URL=https://your.server.example"
+  ```
+
+- As a shell environment variable named `GRASS_ADDONS_BASE_URL` (useful
+  for one-off shell sessions or CI jobs). The gisenv setting takes
+  precedence over the environment variable; if neither is set, the
+  default WinGRASS server is used.
+
+To revert to the default server, unset the value:
+
+```sh
+g.gisenv unset=ADDONS_BASE_URL
+```
+
+Alternative servers are:
+
+- <https://ecodiv.earth/share> (Python extensions only)
+
+Note, settings explained in this section are is honoured on MS-Windows only; on
+Linux/macOS it has no effect.
+
 ## EXAMPLES
 
 ### Download and install of an extension
@@ -132,6 +168,34 @@ convenience, a shorter syntax can be used:
 g.extension r.stream.distance
 ```
 
+### Installing from an alternative addon server (MS-Windows)
+
+On MS-Windows, redirect the addon server to a mirror or private host
+once per session, then use *g.extension* normally — listing and install
+both go through the configured server.
+
+```sh
+# Point at the alternative server (persists across GRASS sessions)
+g.gisenv set="ADDONS_BASE_URL=https://ecodiv.earth/share"
+
+# List what the alternative server provides
+g.extension -l
+
+# Install an extension from it
+g.extension extension=r.tpi
+
+# Revert to the default WinGRASS server
+g.gisenv unset=ADDONS_BASE_URL
+```
+
+For a one-off shell session, set the environment variable instead:
+
+```sh
+# cmd.exe
+set GRASS_ADDONS_BASE_URL=https://ecodiv.earth/share
+g.extension extension=r.tpi
+```
+
 ### Download and install of an extension when behind a proxy
 
 Example for an open http proxy:
@@ -198,8 +262,10 @@ can be used:
 g.extension r.example url=http://example.com/.../r.example?format=zip
 ```
 
-Note that because of MS-Windows operating system architecture, only
-official repository is supported on this platform.
+On Windows, this will work also, but only when pointing at a server with
+pre-compiled addons and set up using the same directory layout as the
+official WinGRASS server, namely `{base}/grass{MM}/addons/grass-{M.M.P}/`
+containing one ZIP per extension and a `modules.xml` listing.
 
 ### Install a specific version from Addons
 
@@ -239,6 +305,11 @@ On MS-Windows, only the official repository is working because there is
 no way of compiling the modules (a Python replacement for Python scripts
 should be implemented).
 
+On Windows, it is now possible to point at an alternative server. However, note
+that this server should be set up using the same directory layout as the
+official WinGRASS server, namely `{base}/grass{MM}/addons/grass-{M.M.P}/`
+containing pre-compiled extensions as ZIP file, and a `modules.xml` listing.
+
 ## TROUBLESHOOTING
 
 Since extensions have to be compiled on Unix based systems (Linux, Mac
@@ -269,3 +340,5 @@ Martin Landa, Czech Technical University in Prague, Czech Republic
 Vaclav Petras, [NCSU GeoForAll
 Lab](https://geospatial.ncsu.edu/geoforall/) (support for general
 sources, partial refactoring)
+Paulo van Breugel, HAS green academy (add option for Windows users to
+point at alternative repositories)
diff --git a/scripts/g.extension/g.extension.py b/scripts/g.extension/g.extension.py
@@ -8,7 +8,7 @@
 #               Vaclav Petras <wenzeslaus gmail com> (support for general sources)
 # PURPOSE:      Tool to download and install extensions into local installation
 #
-# COPYRIGHT:    (C) 2009-2025 by Markus Neteler, and the GRASS Development Team
+# COPYRIGHT:    (C) 2009-2026 by Markus Neteler, and the GRASS Development Team
 #
 #               This program is free software under the GNU General
 #               Public License (>=v2). Read the file COPYING that
@@ -1188,7 +1188,9 @@ def install_extension(source=None, url=None, xmlurl=None, branch=None):
         ret1 = 0
         new_modules_ext = None
         if sys.platform == "win32":
-            ret1, new_modules_ext, new_files_ext = install_extension_win(extension)
+            ret1, new_modules_ext, new_files_ext = install_extension_win(
+                extension, url=url
+            )
         else:
             (
                 ret1,
@@ -1590,21 +1592,59 @@ def install_module_xml(mlist):
     return mlist
 
 
-def install_extension_win(name):
-    """Install extension on MS Windows"""
+def get_addons_base_url():
+    """Resolve the base URL of the addon server (Windows binary repository).
+
+    Precedence (highest first):
+      1. ``ADDONS_BASE_URL`` set via ``g.gisenv set="ADDONS_BASE_URL=..."``.
+         Persists across GRASS sessions and is settable from inside GRASS.
+      2. ``GRASS_ADDONS_BASE_URL`` shell environment variable. Useful for
+         CI / system administrators / one-off shell sessions.
+      3. The built-in default ``http://wingrass.fsv.cvut.cz`` (the official
+         WinGRASS server).
+    """
+    try:
+        gisenv_value = gs.gisenv().get("ADDONS_BASE_URL")
+    except Exception:  # noqa: BLE001
+        # gisenv() can fail outside a GRASS session; fall through.
+        gisenv_value = None
+    if gisenv_value:
+        return gisenv_value.rstrip("/")
+    env_value = os.environ.get("GRASS_ADDONS_BASE_URL")
+    if env_value:
+        return env_value.rstrip("/")
+    return "http://wingrass.fsv.cvut.cz"
+
+
+def install_extension_win(name, url=None):
+    """Install extension on MS Windows."""
     gs.message(
         _("Downloading precompiled GRASS Addons <{}>...").format(options["extension"])
     )
 
-    # build base URL
-    base_url = (
-        "http://wingrass.fsv.cvut.cz/"
-        f"grass{VERSION[0]}{VERSION[1]}/addons/"
-        f"grass-{VERSION[0]}.{VERSION[1]}.{VERSION[2]}"
-    )
+    # Resolve the final ZIP URL.
+    if url:
+        if not url.lower().endswith(".zip"):
+            gs.fatal(
+                _(
+                    "On MS-Windows, the 'url' option must point to a ZIP file "
+                    "(URL ending in '.zip'). To use a different addon server, "
+                    "set the ADDONS_BASE_URL gisenv variable or the "
+                    "GRASS_ADDONS_BASE_URL environment variable instead."
+                )
+            )
+        zip_url = url
+    else:
+        base = get_addons_base_url()
+        base_url = (
+            f"{base}/"
+            f"grass{VERSION[0]}{VERSION[1]}/addons/"
+            f"grass-{VERSION[0]}.{VERSION[1]}.{VERSION[2]}"
+        )
+        zip_url = f"{base_url}/{name}.zip"
 
     # resolve ZIP URL
-    source, url = resolve_source_code(url="{0}/{1}.zip".format(base_url, name))
+    source, url = resolve_source_code(url=zip_url)
 
     # to hide non-error messages from subprocesses
     outdev = open(os.devnull, "w") if gs.verbosity() <= 2 else sys.stdout
@@ -2597,11 +2637,29 @@ def resolve_xmlurl_prefix(url, source=None):
     """
     gs.debug("resolve_xmlurl_prefix(url={0}, source={1})".format(url, source))
     if source in {"official", "official_fork"}:
-        # use pregenerated modules XML file
-        # Define branch to fetch from (latest or current version)
-        version_branch = get_version_branch(VERSION[0])
-
-        url = "https://grass.osgeo.org/addons/{}/".format(version_branch)
+        # On MS-Windows only, the user can redirect both listing and install
+        # to a custom addon server via the ADDONS_BASE_URL gisenv setting or
+        # the GRASS_ADDONS_BASE_URL env var.
+        # On non-Windows, this override is intentionally not honoured
+        override = None
+        if sys.platform == "win32":
+            try:
+                override = gs.gisenv().get("ADDONS_BASE_URL") or os.environ.get(
+                    "GRASS_ADDONS_BASE_URL"
+                )
+            except Exception:  # noqa: BLE001
+                override = os.environ.get("GRASS_ADDONS_BASE_URL")
+        if override:
+            override = override.rstrip("/")
+            url = (
+                f"{override}/grass{VERSION[0]}{VERSION[1]}/addons/"
+                f"grass-{VERSION[0]}.{VERSION[1]}.{VERSION[2]}/"
+            )
+        else:
+            # use pregenerated modules XML file
+            # Define branch to fetch from (latest or current version)
+            version_branch = get_version_branch(VERSION[0])
+            url = "https://grass.osgeo.org/addons/{}/".format(version_branch)
     # else try to get extensions XMl from SVN repository (provided URL)
     # the exact action depends on subsequent code (somewhere)
 
@@ -2930,7 +2988,7 @@ def main():
     if options["operation"] == "add":
         check_dirs()
         if sys.platform == "win32":
-            install_extension()
+            install_extension(url=original_url)
         else:
             if original_url == "" or flags["o"]:
                 # Query GitHub API only if extension will be downloaded