diff --git a/src/sigal/gallery.py b/src/sigal/gallery.py
index eed4a41..7a41210 100644
--- a/src/sigal/gallery.py
+++ b/src/sigal/gallery.py
@@ -597,6 +597,9 @@ class Album:
             self.logger.debug("Thumbnail for %r : %s", self, self._thumbnail)
             return self._thumbnail
 
+        def _join_url(a, b):
+            return "./" + os.path.normpath(url_quote(a) + "/" + b)
+
         # find and return the first landscape image
         for f in self.medias:
             ext = splitext(f.dst_filename)[1]
@@ -611,7 +614,7 @@ class Album:
 
             if size["width"] > size["height"]:
                 try:
-                    self._thumbnail = url_quote(self.name) + "/" + f.thumbnail
+                    self._thumbnail = _join_url(self.name, f.thumbnail)
                 except Exception as e:
                     self.logger.info(
                         "Failed to get thumbnail for %s: %s", f.dst_filename, e
@@ -629,7 +632,7 @@ class Album:
             for media in self.medias:
                 if media.thumbnail is not None:
                     try:
-                        self._thumbnail = url_quote(self.name) + "/" + media.thumbnail
+                        self._thumbnail = _join_url(self.name, media.thumbnail)
                     except Exception as e:
                         self.logger.info(
                             "Failed to get thumbnail for %s: %s",
@@ -651,7 +654,7 @@ class Album:
         if not self._thumbnail:
             for path, album in self.gallery.get_albums(self.path):
                 if album.thumbnail:
-                    self._thumbnail = url_quote(self.name) + "/" + album.thumbnail
+                    self._thumbnail = _join_url(self.name, album.thumbnail)
                     self.logger.debug(
                         "Using thumbnail from sub-directory for %r : %s",
                         self,
diff --git a/tests/test_gallery.py b/tests/test_gallery.py
index f0ce811..af9d25b 100644
--- a/tests/test_gallery.py
+++ b/tests/test_gallery.py
@@ -24,14 +24,14 @@ REF = {
     "dir1": {
         "title": "An example gallery",
         "name": "dir1",
-        "thumbnail": "dir1/test1/thumbnails/11.tn.jpg",
+        "thumbnail": "./dir1/test1/thumbnails/11.tn.jpg",
         "subdirs": ["test1", "test2", "test3"],
         "medias": [],
     },
     "dir1/test1": {
         "title": "An example sub-category",
         "name": "test1",
-        "thumbnail": "test1/thumbnails/11.tn.jpg",
+        "thumbnail": "./test1/thumbnails/11.tn.jpg",
         "subdirs": [],
         "medias": [
             "11.jpg",
@@ -43,21 +43,21 @@ REF = {
     "dir1/test2": {
         "title": "test2",
         "name": "test2",
-        "thumbnail": "test2/thumbnails/21.tn.tiff",
+        "thumbnail": "./test2/thumbnails/21.tn.tiff",
         "subdirs": [],
         "medias": ["21.tiff", "22.jpg", "CMB_Timeline300_no_WMAP.jpg"],
     },
     "dir1/test3": {
         "title": "01 First title alphabetically",
         "name": "test3",
-        "thumbnail": "test3/thumbnails/3.tn.jpg",
+        "thumbnail": "./test3/thumbnails/3.tn.jpg",
         "subdirs": [],
         "medias": ["3.jpg"],
     },
     "dir2": {
         "title": "Another example gallery with a very long name",
         "name": "dir2",
-        "thumbnail": "dir2/thumbnails/m57_the_ring_nebula-587px.tn.jpg",
+        "thumbnail": "./dir2/thumbnails/m57_the_ring_nebula-587px.tn.jpg",
         "subdirs": [],
         "medias": [
             "KeckObservatory20071020.jpg",
@@ -69,21 +69,21 @@ REF = {
     "accentué": {
         "title": "accentué",
         "name": "accentué",
-        "thumbnail": "accentu%C3%A9/thumbnails/h%C3%A9lico%C3%AFde.tn.jpg",
+        "thumbnail": "./accentu%C3%A9/thumbnails/h%C3%A9lico%C3%AFde.tn.jpg",
         "subdirs": [],
         "medias": ["hélicoïde.jpg", "11.jpg"],
     },
     "video": {
         "title": "video",
         "name": "video",
-        "thumbnail": "video/thumbnails/example%20video.tn.jpg",
+        "thumbnail": "./video/thumbnails/example%20video.tn.jpg",
         "subdirs": [],
         "medias": ["example video.ogv"],
     },
     "webp": {
         "title": "webp",
         "name": "webp",
-        "thumbnail": "webp/thumbnails/_MG_7805_lossy80.tn.webp",
+        "thumbnail": "./webp/thumbnails/_MG_7805_lossy80.tn.webp",
         "subdirs": [],
         "medias": ["_MG_7805_lossy80.webp", "_MG_7808_lossy80.webp"],
     },
@@ -123,7 +123,7 @@ def test_media_orig(settings, tmpdir):
 
     m = Video("example video.ogv", "video", settings)
     assert m.dst_filename == "example video.webm"
-    assert m.big_url == "original/example%20video.ogv"
+    assert m.big_url == "./original/example%20video.ogv"
     assert os.path.isfile(join(settings["destination"], m.path, m.big))
 
     settings["use_orig"] = True
@@ -180,7 +180,7 @@ def test_image(settings, tmpdir):
     assert m.exif["datetime"] == "22/01/2006"
 
     os.makedirs(join(settings["destination"], "dir1", "test1", "thumbnails"))
-    assert m.thumbnail == join("thumbnails", "11.tn.jpg")
+    assert m.thumbnail == join(".", "thumbnails", "11.tn.jpg")
     assert os.path.isfile(m.thumb_path)
 
 
@@ -195,7 +195,7 @@ def test_video(settings, tmpdir):
     assert m.dst_path == join(settings["destination"], file_path)
 
     os.makedirs(join(settings["destination"], "video", "thumbnails"))
-    assert m.thumbnail == join("thumbnails", "example%20video.tn.jpg")
+    assert m.thumbnail == join(".", "thumbnails", "example%20video.tn.jpg")
     assert os.path.isfile(m.thumb_path)
 
 
@@ -330,7 +330,7 @@ def test_gallery(settings, tmp_path, caplog):
         html = f.read()
 
     assert "<title>Sigal test gallery - Sigal test gallery ☺</title>" in html
-    assert '<link rel="stylesheet" href="static/my.css">' in html
+    assert '<link rel="stylesheet" href="./static/my.css">' in html
 
     logger = logging.getLogger("sigal")
     logger.setLevel(logging.DEBUG)
@@ -454,4 +454,4 @@ def test_thumbnail_with_img_format(settings, tmp_path, thumbnail):
 
     assert (tmp_path / "build" / "test1" / "outdoor.tn.jpg").is_file()
     index = (tmp_path / "build" / "index.html").read_text()
-    assert 'src="test1/outdoor.tn.jpg" class="album_thumb"' in index
+    assert 'src="./test1/outdoor.tn.jpg" class="album_thumb"' in index
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 317e7f9..ad46eba 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -88,14 +88,14 @@ def test_check_or_create_dir(tmpdir):
 
 
 def test_url_from_path():
-    assert utils.url_from_path(os.sep.join(["foo", "bar"])) == "foo/bar"
+    assert utils.url_from_path(os.sep.join(["foo", "bar"])) == "./foo/bar"
 
 
 def test_url_from_windows_path(monkeypatch):
     monkeypatch.setattr("os.sep", "\\")
     path = os.sep.join(["foo", "bar"])
     assert path == r"foo\bar"
-    assert utils.url_from_path(path) == "foo/bar"
+    assert utils.url_from_path(path) == "./foo/bar"
 
 
 def test_read_markdown():