diff --git a/TESTING.md b/TESTING.md
index f81916ab..4dec7769 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -2465,8 +2465,12 @@ files to the system trash. **No code path unlinks or overwrites a media file.**
   `.Trash/$uid` or `.Trash-$uid`), reserve the name with `O_EXCL` and move with
   `renameat2(RENAME_NOREPLACE)`; without it, across devices, on a read-only mount or with
   a trash inside an output root the move is refused (`no-trash`, `trash-in-root`). Windows
-  and macOS report `no-trash` until their own backends land; library-only removal works
-  everywhere. Tests use `tests/fake_trash.py`; the browser test server installs it, so no
+  never uses the Recycle Bin (#500, maintainer ruling (a)): files larger than the bin's
+  capacity are deleted permanently and IFileOperation's `PreDeleteItem` guard cannot detect
+  it (native probe runs 40951037575, 40953347904), so every file answers `windows-recycle`
+  ("Moving files to the Recycle Bin isn't available on Windows: files larger than the bin's
+  capacity would be deleted permanently."). macOS reports `no-trash` until #499 lands;
+  library-only removal works everywhere. Tests use `tests/fake_trash.py`; the browser test server installs it, so no
   test touches a real trash.
 
 ### Prompt library cards and recorded deviations (#249 PR E)
diff --git a/py/api/image_delete.py b/py/api/image_delete.py
index fe011149..b83c767f 100644
--- a/py/api/image_delete.py
+++ b/py/api/image_delete.py
@@ -80,6 +80,10 @@ REASONS = {
     trash.TRASH_IN_ROOT: "This drive's trash is inside an output folder.",
     trash.LOCKED: "The file is open in another program. Close it and try again.",
     trash.FAILED: "The file could not be moved to the trash.",
+    trash.WINDOWS_RECYCLE: (
+        "Moving files to the Recycle Bin isn't available on Windows: files larger "
+        "than the bin's capacity would be deleted permanently."
+    ),
     "not-attempted": "Not attempted: the job stopped after an error.",
 }
 _PROBLEM_CODES = {
diff --git a/tests/js/workspace-images-delete.test.js b/tests/js/workspace-images-delete.test.js
index 90782294..d03e8c81 100644
--- a/tests/js/workspace-images-delete.test.js
+++ b/tests/js/workspace-images-delete.test.js
@@ -65,6 +65,8 @@ test('sentences follow the mode and the backup policy', () => {
     assert.deepEqual(deleteSentences(plan(), 'trash'), [SENTENCES.trash, USE_LIBRARY_ONLY]);
     const nowhere = plan({ trash: { count: 0 }, trash_refused: { count: 3, rows: [] } });
     assert.deepEqual(deleteSentences(nowhere, 'trash'), [SENTENCES.trash, NO_TRASH_HERE, USE_LIBRARY_ONLY]);
+    // #500: no "yet" (Windows is unavailable by design); each file's reason says why.
+    assert.equal(NO_TRASH_HERE, 'Moving to the trash is not available for these files; each one lists why.');
     assert.deepEqual(deleteSentences(plan({ trash_refused: { count: 0 } }), 'trash'), [SENTENCES.trash]);
 });
 
diff --git a/tests/test_image_delete_routes.py b/tests/test_image_delete_routes.py
index 1fb364df..53f34471 100644
--- a/tests/test_image_delete_routes.py
+++ b/tests/test_image_delete_routes.py
@@ -306,6 +306,13 @@ class TestFileCheck(ImageDeleteTestCase):
             file_check(str(self.output_dir / "ok.png"), root, "ok.png")[0]
         )
 
+    def test_windows_reason_says_why_plainly(self):
+        self.assertEqual(
+            image_delete.REASONS["windows-recycle"],
+            "Moving files to the Recycle Bin isn't available on Windows: files "
+            "larger than the bin's capacity would be deleted permanently.",
+        )
+
     def test_reasons_cover_every_code(self):
         from utils import trash
 
@@ -324,7 +331,8 @@ class TestNativeBackend(ImageDeleteTestCase):
         native_trash = sys.platform not in ("win32", "darwin")
         if not native_trash:
             self.assertEqual(plan["trash"], {"count": 0})
-            self.assertEqual(plan["trash_refused"]["counts"], {"no-trash": 1})
+            code = "windows-recycle" if sys.platform == "win32" else "no-trash"
+            self.assertEqual(plan["trash_refused"]["counts"], {code: 1})
         body = await self.post(APPLY, {"token": plan["token"], "mode": "library"}, 202)
         job = self.api._jobs.get(body["job"]["id"])
         await asyncio.wait_for(asyncio.shield(job.task), DISK_BOUND_SECONDS)
diff --git a/tests/test_trash_freedesktop.py b/tests/test_trash_freedesktop.py
index a0f3f3ec..dd8ab6d5 100644
--- a/tests/test_trash_freedesktop.py
+++ b/tests/test_trash_freedesktop.py
@@ -285,6 +285,20 @@ class UnavailableBackendTests(unittest.TestCase):
                 )
         self.assertIsInstance(trash.default_backend("linux"), trash.FreedesktopBackend)
 
+    def test_windows_says_why_the_recycle_bin_is_not_used(self):
+        # #500 ruling (a): the Recycle Bin can delete permanently, so it is never used.
+        backend = trash.default_backend("win32")
+        self.assertEqual(
+            backend.available("C:/x/a.png", ["C:/x"]), trash.WINDOWS_RECYCLE
+        )
+        with self.assertRaises(trash.TrashRefused) as caught:
+            backend.move("C:/x/a.png", ["C:/x"])
+        self.assertEqual(caught.exception.code, trash.WINDOWS_RECYCLE)
+        self.assertIn(trash.WINDOWS_RECYCLE, trash.CODES)
+        self.assertEqual(
+            trash.default_backend("darwin").available("/x", ["/"]), trash.NO_TRASH
+        )
+
     def test_module_functions_use_the_replaceable_backend(self):
         fake = mock.Mock()
         fake.available.return_value = "network"
diff --git a/utils/trash.py b/utils/trash.py
index 242236b5..729f6d66 100644
--- a/utils/trash.py
+++ b/utils/trash.py
@@ -14,8 +14,9 @@ same mount, else the file's mount's ``.Trash/$uid`` (only under a real, sticky
 ``.Trash``) or ``.Trash-$uid``. Names are reserved by creating the
 ``.trashinfo`` with ``O_EXCL`` and the file is moved with
 ``renameat2(RENAME_NOREPLACE)``; without that call the move is refused.
-Windows and macOS have no backend yet (:class:`UnavailableBackend`): their
-own PRs add one with a native proof.
+Windows never uses the Recycle Bin (#500: files over its capacity are deleted
+permanently, undetectably), so it answers ``windows-recycle``; macOS has no
+backend yet (#499). Both use :class:`UnavailableBackend`.
 
 ``BACKEND`` is the one replaceable seam; tests install a fake.
 """
@@ -36,7 +37,11 @@ TRASH_IN_ROOT = "trash-in-root"
 PATH_TOO_LONG = "path-too-long"
 LOCKED = "locked"
 FAILED = "failed"
-CODES = frozenset({NO_TRASH, NETWORK, TRASH_IN_ROOT, PATH_TOO_LONG, LOCKED, FAILED})
+# Windows never uses the Recycle Bin (#500): it can delete permanently.
+WINDOWS_RECYCLE = "windows-recycle"
+CODES = frozenset(
+    {NO_TRASH, NETWORK, TRASH_IN_ROOT, PATH_TOO_LONG, LOCKED, FAILED, WINDOWS_RECYCLE}
+)
 
 HOME_TRASH_LABEL = "home trash"
 RENAME_NOREPLACE = 1
@@ -177,13 +182,16 @@ def _owned_folder(path: str, uid: int, *, create: bool) -> bool:
 
 
 class UnavailableBackend:
-    """No trash on this system: every move is refused, nothing is touched."""
+    """No trash on this system: every move is refused with *code*, untouched."""
+
+    def __init__(self, code: str = NO_TRASH):
+        self.code = code
 
     def available(self, path: str, roots) -> str | None:
-        return NO_TRASH
+        return self.code
 
     def move(self, path: str, roots) -> str:
-        raise TrashRefused(NO_TRASH)
+        raise TrashRefused(self.code)
 
 
 class FreedesktopBackend:
@@ -346,7 +354,12 @@ class FreedesktopBackend:
 
 def default_backend(platform: str = sys.platform):
     """The backend for *platform*; Windows and macOS have none yet (#480)."""
-    if platform in ("win32", "darwin") or platform.startswith("cygwin"):
+    if platform == "win32" or platform.startswith("cygwin"):
+        # #500, ruling (a): Windows deletes files larger than the Recycle Bin's
+        # capacity permanently, and IFileOperation's PreDeleteItem guard cannot
+        # tell (native probe runs 40951037575, 40953347904).
+        return UnavailableBackend(WINDOWS_RECYCLE)
+    if platform == "darwin":
         return UnavailableBackend()
     return FreedesktopBackend()
 
diff --git a/web/js/workspace/images-delete.mjs b/web/js/workspace/images-delete.mjs
index 7f53015e..28b92219 100644
--- a/web/js/workspace/images-delete.mjs
+++ b/web/js/workspace/images-delete.mjs
@@ -32,7 +32,7 @@ export const REVIEW_FAILED = 'The review failed. Nothing was changed.';
 export const SOURCE_CHANGED = 'The sources changed. Refresh the images and try again.';
 export const STORAGE_CHANGED = 'Prompt storage was restored. Reopen Delete.';
 export const USE_LIBRARY_ONLY = 'To remove these files from the library anyway, choose “Remove from the library only”.';
-export const NO_TRASH_HERE = 'Moving to the trash is not available on this system yet.';
+export const NO_TRASH_HERE = 'Moving to the trash is not available for these files; each one lists why.';
 const SENTENCES = Object.freeze({
     libraryBackup: 'Removed images stay hidden unless the file is modified or replaced. Their tags, category, collections '
         + 'and favorite can only be recovered by restoring the safety backup, which also undoes every later change.',