diff --git a/src/calibre/gui2/viewer/web_view.py b/src/calibre/gui2/viewer/web_view.py
index 3463738370..14fe4a5934 100644
--- a/src/calibre/gui2/viewer/web_view.py
+++ b/src/calibre/gui2/viewer/web_view.py
@@ -77,18 +77,26 @@ def get_data(name):
     return None, None
 
 
-def background_image():
-    ans = getattr(background_image, 'ans', None)
-    if ans is None:
+@lru_cache(maxsize=4)
+def background_image(encoded_fname=''):
+    if not encoded_fname:
         img_path = os.path.join(viewer_config_dir, 'bg-image.data')
-        if os.path.exists(img_path):
+        try:
             with open(img_path, 'rb') as f:
                 data = f.read()
-                mt, data = data.split(b'|', 1)
-        else:
-            ans = b'image/jpeg', b''
-        ans = background_image.ans = mt.decode('utf-8'), data
-    return ans
+            mt, data = data.split(b'|', 1)
+            mt = mt.decode()
+            return mt, data
+        except FileNotFoundError:
+            return 'image/jpeg', b''
+    fname = bytes.fromhex(encoded_fname).decode()
+    img_path = os.path.join(viewer_config_dir, 'background-images', fname)
+    mt = guess_type(fname)[0] or 'image/jpeg'
+    try:
+        with open(img_path, 'rb') as f:
+            return mt, f.read()
+    except FileNotFoundError:
+        return mt, b''
 
 
 @lru_cache(maxsize=2)
@@ -161,10 +169,11 @@ class UrlSchemeHandler(QWebEngineUrlSchemeHandler):
             send_reply(rq, set_book_path.manifest_mime, data)
         elif name == 'reader-background':
             mt, data = background_image()
-            if data:
-                send_reply(rq, mt, data)
-            else:
-                rq.fail(QWebEngineUrlRequestJob.Error.UrlNotFound)
+            send_reply(rq, mt, data) if data else rq.fail(QWebEngineUrlRequestJob.Error.UrlNotFound)
+        elif name.startswith('reader-background-'):
+            encoded_fname = name[len('reader-background-'):]
+            mt, data = background_image(encoded_fname)
+            send_reply(rq, mt, data) if data else rq.fail(QWebEngineUrlRequestJob.Error.UrlNotFound)
         elif name.startswith('mathjax/'):
             handle_mathjax_request(rq, name)
         elif not name:
@@ -693,14 +702,16 @@ class WebView(RestartingWebEngineView):
         self.execute_when_ready('show_home_page')
 
     def change_background_image(self, img_id):
-        files = choose_images(self, 'viewer-background-image', _('Choose background image'), formats=['png', 'gif', 'jpg', 'jpeg'])
+        files = choose_images(self, 'viewer-background-image', _('Choose background image'), formats=['png', 'gif', 'jpg', 'jpeg', 'webp'])
         if files:
             img = files[0]
-            with open(img, 'rb') as src, open(os.path.join(viewer_config_dir, 'bg-image.data'), 'wb') as dest:
-                dest.write(as_bytes(guess_type(img)[0] or 'image/jpeg') + b'|')
-                shutil.copyfileobj(src, dest)
+            d = os.path.join(viewer_config_dir, 'background-images')
+            os.makedirs(d, exist_ok=True)
+            fname = os.path.basename(img)
+            shutil.copyfile(img, os.path.join(d, fname))
             background_image.ans = None
-            self.execute_when_ready('background_image_changed', img_id)
+            encoded = fname.encode().hex()
+            self.execute_when_ready('background_image_changed', img_id, f'{FAKE_PROTOCOL}://{FAKE_HOST}/reader-background-{encoded}')
 
     def goto_frac(self, frac):
         self.execute_when_ready('goto_frac', frac)
diff --git a/src/calibre/srv/content.py b/src/calibre/srv/content.py
index 90c37a4a69..1f06062b1d 100644
--- a/src/calibre/srv/content.py
+++ b/src/calibre/srv/content.py
@@ -30,7 +30,9 @@ from calibre.srv.routes import endpoint, json
 from calibre.srv.utils import get_db, get_use_roman, http_date
 from calibre.utils.config_base import tweaks
 from calibre.utils.date import timestampfromdt
-from calibre.utils.filenames import ascii_filename, atomic_rename
+from calibre.utils.filenames import (
+    ascii_filename, atomic_rename, make_long_path_useable,
+)
 from calibre.utils.img import image_from_data, scale_image
 from calibre.utils.localization import _
 from calibre.utils.resources import get_image_path as I, get_path as P
@@ -303,6 +305,19 @@ def icon(ctx, rd, which):
         return ans
 
 
+@endpoint('/reader-background/{encoded_fname}', android_workaround=True)
+def reader_background(ctx, rd, encoded_fname):
+    base = os.path.abspath(os.path.normapth(os.path.join(config_dir, 'viewer', 'background-images')))
+    fname = bytes.fromhex(encoded_fname)
+    q = os.path.abspath(os.path.normpath(os.path.join(base, fname)))
+    if not q.startswith(base):
+        raise HTTPNotFound(f'Reader background {encoded_fname} not found')
+    try:
+        return share_open(make_long_path_useable(q), 'rb')
+    except FileNotFoundError:
+        raise HTTPNotFound(f'Reader background {encoded_fname} not found')
+
+
 @endpoint('/get/{what}/{book_id}/{library_id=None}', android_workaround=True)
 def get(ctx, rd, what, book_id, library_id):
     book_id, rest = book_id.partition('_')[::2]
diff --git a/src/pyj/read_book/prefs/user_stylesheet.pyj b/src/pyj/read_book/prefs/user_stylesheet.pyj
index 450f7072fa..77e04657c2 100644
--- a/src/pyj/read_book/prefs/user_stylesheet.pyj
+++ b/src/pyj/read_book/prefs/user_stylesheet.pyj
@@ -3,14 +3,16 @@
 from __python__ import bound_methods, hash_literals
 
 from elementmaker import E
-from gettext import gettext as _
 
+from ajax import absolute_path
 from book_list.globals import get_session_data
 from dom import ensure_id, unique_id
+from encodings import hexlify
+from gettext import gettext as _
 from read_book.globals import runtime, ui_operations
 from read_book.prefs.utils import create_button_box
 from session import session_defaults
-from viewer.constants import READER_BACKGROUND_URL
+from viewer.constants import FAKE_HOST, FAKE_PROTOCOL
 from widgets import create_button
 
 BLANK = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7'
@@ -21,19 +23,33 @@ def change_background_image(img_id):
 
 
 def clear_image(img_id):
-    document.getElementById(img_id).src = BLANK
+    i = document.getElementById(img_id)
+    i.src = BLANK
+    i.dataset.url = ''
+
+
+def modify_background_image_url_for_fetch(url):
+    if not url:
+        return BLANK
+    if runtime.is_standalone_viewer:
+        if url.startswith(f'{FAKE_PROTOCOL}:'):
+            return url
+        encoded = hexlify(url)
+        return f'{FAKE_PROTOCOL}://{FAKE_HOST}/reader-background-{encoded}'
+    if url.startswith(f'{FAKE_PROTOCOL}:'):
+        x = str.split(url, '/')[-1].partition('?')[0].partition('-')[2]
+        return absolute_path(f'reader-background/{x}')
+    return url
 
 
 def standalone_background_widget(sd):
-    if sd.get('background_image'):
-        src = READER_BACKGROUND_URL
-    else:
-        src = BLANK
+    url = sd.get('background_image')
+    src = modify_background_image_url_for_fetch(url)
     img_id = unique_id('bg-image')
 
     return E.div(
         style='display: flex; align-items: center',
-        E.div(E.img(src=src, id=img_id, class_='bg-image-preview', style='width: 75px; height: 75px; border: solid 1px')),
+        E.div(E.img(src=src, data_url=url, id=img_id, class_='bg-image-preview', style='width: 75px; height: 75px; border: solid 1px')),
         E.div('\xa0', style='margin: 0.5rem'),
         create_button(_('Change image'), action=change_background_image.bind(None, img_id)),
         E.div('\xa0', style='margin: 0.5rem'),
@@ -77,7 +93,8 @@ def restore_defaults():
     container = document.getElementById(create_user_stylesheet_panel.container_id)
     container.querySelector('[name=user-stylesheet]').value = ''
     if runtime.is_standalone_viewer:
-        clear_image(container.querySelector('img').id)
+        i = container.querySelector('img')
+        clear_image(i.id)
     else:
         container.querySelector('[name=background_image]').value = ''
     container.querySelector('select[name=background_image_style]').value = session_defaults().background_image_style
@@ -132,8 +149,8 @@ def commit_user_stylesheet(onchange, container):
         sd.set('user_stylesheet', val)
         changed = True
     if runtime.is_standalone_viewer:
-        bg_image = container.querySelector('img.bg-image-preview').src
-        if bg_image is BLANK:
+        bg_image = container.querySelector('img.bg-image-preview').dataset.url
+        if bg_image is BLANK or not bg_image:
             bg_image = None
     else:
         bg_image = container.querySelector('input[name=background_image]').value
diff --git a/src/pyj/read_book/view.pyj b/src/pyj/read_book/view.pyj
index 3d8d86858b..4dc0e7a66f 100644
--- a/src/pyj/read_book/view.pyj
+++ b/src/pyj/read_book/view.pyj
@@ -33,6 +33,7 @@ from read_book.prefs.head_foot import render_head_foot
 from read_book.prefs.scrolling import (
     MIN_SCROLL_SPEED_AUTO as SCROLL_SPEED_STEP, change_scroll_speed
 )
+from read_book.prefs.user_stylesheet import modify_background_image_url_for_fetch
 from read_book.read_aloud import ReadAloud
 from read_book.read_audio_ebook import ReadAudioEbook
 from read_book.resources import load_resources
@@ -49,7 +50,6 @@ from utils import (
     default_context_menu_should_be_allowed, html_escape, is_ios, parse_url_params,
     safe_set_inner_html, username_key
 )
-from viewer.constants import READER_BACKGROUND_URL
 
 add_extra_css(def():
     sel = '.book-side-margin'
@@ -851,7 +851,7 @@ class View:
         iframe.style.backgroundColor = ans.background or 'white'
         bg_image = sd.get('background_image')
         if bg_image:
-            iframe.style.backgroundImage = f'url({READER_BACKGROUND_URL}?{Date().getTime()})' if runtime.is_standalone_viewer else f'url({bg_image})'
+            iframe.style.backgroundImage = f'url({modify_background_image_url_for_fetch(bg_image)})'
         else:
             iframe.style.backgroundImage = 'none'
         if sd.get('background_image_style') is 'scaled':
diff --git a/src/pyj/viewer-main.pyj b/src/pyj/viewer-main.pyj
index c1729e912f..8e61ba3462 100644
--- a/src/pyj/viewer-main.pyj
+++ b/src/pyj/viewer-main.pyj
@@ -26,7 +26,7 @@ from read_book.prefs.head_foot import set_time_formatter
 from read_book.view import View
 from session import local_storage, session_defaults, default_interface_data
 from utils import debounce, encode_query_with_path, parse_url_params
-from viewer.constants import FAKE_HOST, FAKE_PROTOCOL, READER_BACKGROUND_URL
+from viewer.constants import FAKE_HOST, FAKE_PROTOCOL
 
 runtime.is_standalone_viewer = True
 runtime.FAKE_HOST = FAKE_HOST
@@ -267,10 +267,11 @@ def goto_frac(frac):
 
 
 @from_python
-def background_image_changed(img_id):
+def background_image_changed(img_id, url):
     img = document.getElementById(img_id)
     if img:
-        img.src = READER_BACKGROUND_URL + '?' + Date().getTime()
+        img.src = f'{url}?{Date().getTime()}'
+        img.dataset.url = url
 
 
 @from_python
diff --git a/src/pyj/viewer/constants.pyj b/src/pyj/viewer/constants.pyj
index 5ee296b986..aaabf5aefe 100644
--- a/src/pyj/viewer/constants.pyj
+++ b/src/pyj/viewer/constants.pyj
@@ -5,4 +5,3 @@ from __python__ import bound_methods, hash_literals
 
 FAKE_PROTOCOL = '__FAKE_PROTOCOL__'
 FAKE_HOST = '__FAKE_HOST__'
-READER_BACKGROUND_URL = f'{FAKE_PROTOCOL}://{FAKE_HOST}/reader-background'