diff --git a/src/calibre/scraper/simple.py b/src/calibre/scraper/simple.py
index b41ed65a68..20c0a97cf5 100644
--- a/src/calibre/scraper/simple.py
+++ b/src/calibre/scraper/simple.py
@@ -9,11 +9,15 @@ import secrets
 import sys
 import time
 from functools import lru_cache
-from qt.core import QApplication, QEventLoop, QUrl
+from qt.core import QApplication, QEventLoop, QLoggingCategory, QUrl
 from qt.webengine import QWebEnginePage, QWebEngineProfile, QWebEngineSettings
+from threading import Lock
 
-from calibre.constants import cache_dir
+from calibre.constants import cache_dir, iswindows
 from calibre.gui2.webengine import create_script, insert_scripts
+from calibre.ptempfile import PersistentTemporaryFile
+from calibre.utils.ipc.simple_worker import start_pipe_worker
+from calibre.utils.filenames import retry_on_fail
 
 
 def canonicalize_qurl(qurl):
@@ -123,13 +127,97 @@ class SimpleScraper(QWebEnginePage):
             del self.current_fetch
 
 
+def worker_main(source):
+    QLoggingCategory.setFilterRules('''\
+qt.webenginecontext.info=false
+''')
+    from calibre.gui2 import must_use_qt
+    must_use_qt()
+    s = SimpleScraper(source)
+    for line in sys.stdin.buffer:
+        line = line.strip()
+        try:
+            cmd, rest = line.split(b':', 1)
+        except Exception:
+            continue
+        if cmd == b'EXIT':
+            raise SystemExit(int(rest))
+        if cmd == b'FETCH':
+            try:
+                html = s.fetch(QUrl.fromEncoded(json.loads(rest).encode('utf-8')))
+            except Exception as e:
+                import traceback
+                result = {'ok': False, 'tb': traceback.format_exc(), 'err': str(e)}
+            else:
+                with PersistentTemporaryFile(suffix='-scraper-result.html') as t:
+                    t.write(html.encode('utf-8'))
+                result = {'ok': True, 'html_file': t.name}
+            print(json.dumps(result), flush=True)
+
+
+class Overseer:
+
+    def __init__(self):
+        self.lock = Lock()
+        self.workers = {}
+
+    def worker_for_source(self, source):
+        with self.lock:
+            ans = self.workers.get(source)
+            if ans is None:
+                w = start_pipe_worker(f'from calibre.scraper.simple import worker_main; worker_main({source!r})')
+                ans = self.workers[source] = w
+        return ans
+
+    def fetch_url(self, source, url_or_qurl):
+        w = self.worker_for_source(source)
+        if isinstance(url_or_qurl, str):
+            url_or_qurl = QUrl(url_or_qurl)
+        w.stdin.write(b'FETCH:')
+        w.stdin.write(json.dumps(bytes(url_or_qurl.toEncoded()).decode('utf-8')).encode('utf-8'))
+        w.stdin.write(b'\n')
+        w.stdin.flush()
+        output = json.loads(w.stdout.readline())
+        if not output['ok']:
+            raise ValueError(output['err'])
+        with open(output['html_file'], 'rb') as f:
+            html = f.read().decode('utf-8')
+        retry_on_fail(os.remove, output['html_file'])
+        return html
+
+    def __del__(self):
+        with self.lock:
+            for w in self.workers.values():
+                w.stdin.write(b'EXIT:0\n')
+                w.stdin.flush()
+            for w in self.workers.values():
+                if w.wait(0.2) is None:
+                    w.terminate()
+                    if not iswindows:
+                        if w.wait(0.1) is None:
+                            w.kill()
+            self.workers.clear()
+
+
 def find_tests():
     import unittest
+    from lxml.html import fromstring, tostring
+    import re
 
     class TestSimpleWebEngineScraper(unittest.TestCase):
 
         def test_dom_load(self):
-            return
+            overseer = Overseer()
+            for f in ('book', 'nav'):
+                path = P(f'templates/new_{f}.html', allow_user_override=False)
+                url = QUrl.fromLocalFile(path)
+                html = overseer.fetch_url('test', url)
+
+                def c(a):
+                    ans = tostring(fromstring(a.encode('utf-8')), pretty_print=True, encoding='unicode')
+                    return re.sub(r'\s+', ' ', ans)
+                self.assertEqual(c(html), c(open(path, 'rb').read().decode('utf-8')))
+            self.assertRaises(ValueError, overseer.fetch_url, 'test', 'file:///does-not-exist.html')
 
     return unittest.defaultTestLoader.loadTestsFromTestCase(TestSimpleWebEngineScraper)