diff --git a/downloads/management/commands/add_file.py b/downloads/management/commands/add_file.py
index 19d7722b..e59be669 100644
--- a/downloads/management/commands/add_file.py
+++ b/downloads/management/commands/add_file.py
@@ -29,7 +29,7 @@ def handle(self, *args, **options):
             dlpath = dlpath[:-1]
 
         for f in options["file"]:
-            self.stdout.write("Adding %s..." % f)
+            self.stdout.write(f"Adding {f}...")
             filename = os.path.basename(f)
 
             with open(f, "rb") as handle:
diff --git a/downloads/models.py b/downloads/models.py
index e42f249a..74d5a61a 100644
--- a/downloads/models.py
+++ b/downloads/models.py
@@ -113,10 +113,7 @@ def save(self, *args, **kwargs):
                 programurl=f"https://{current_site}{PROGRAM_URLS[self.program]}",
                 versionurl=f"https://{current_site}{self.get_absolute_url()}",
             )
-            body = (
-                "Full list of changes:\n\n%s\n\nYou can download it from <https://wammu.eu/download/>.\n\nSupport this program by donations <https://wammu.eu/donate/>."
-                % self.changelog
-            )
+            body = f"Full list of changes:\n\n{self.changelog}\n\nYou can download it from <https://wammu.eu/download/>.\n\nSupport this program by donations <https://wammu.eu/donate/>."
             title = f"{get_program(self.program)} {self.version}"
             slug = "{}-{}".format(
                 self.program,
diff --git a/downloads/views.py b/downloads/views.py
index 463f34ac..bd406c40 100644
--- a/downloads/views.py
+++ b/downloads/views.py
@@ -12,7 +12,8 @@
 
 def detail(request, program):
     if program not in (x[0] for x in PROGRAM_CHOICES):
-        raise Http404("No such program %s." % program)
+        msg = f"No such program {program}."
+        raise Http404(msg)
 
     downloads = get_current_downloads(program)
 
@@ -23,7 +24,8 @@ def detail(request, program):
         testing_release, testing_downloads = (None, None)
 
     if stable_downloads.count() == 0:
-        raise Http404("No such download option %s." % program)
+        msg = f"No such download option {program}."
+        raise Http404(msg)
 
     return render(
         request,
@@ -64,13 +66,14 @@ def download(request):
 
 def doap(request, program):
     if program not in (x[0] for x in PROGRAM_CHOICES):
-        raise Http404("No such program %s." % program)
+        msg = f"No such program {program}."
+        raise Http404(msg)
 
     downloads = get_current_downloads(program)
 
     return render(
         request,
-        "downloads/doap/%s.xml" % program,
+        f"downloads/doap/{program}.xml",
         {
             "downloads": downloads[0][1],
             "release": downloads[0][0],
@@ -81,7 +84,8 @@ def doap(request, program):
 
 def pad(request, program):
     if program not in (x[0] for x in PROGRAM_CHOICES):
-        raise Http404("No such program %s." % program)
+        msg = f"No such program {program}."
+        raise Http404(msg)
 
     downloads = get_current_downloads(program)
 
@@ -96,7 +100,7 @@ def pad(request, program):
 
     return render(
         request,
-        "downloads/pad/%s.xml" % program,
+        f"downloads/pad/{program}.xml",
         {
             "download": download,
             "release": release,
diff --git a/news/views.py b/news/views.py
index 88e20373..2f83eb42 100644
--- a/news/views.py
+++ b/news/views.py
@@ -30,7 +30,7 @@ def category(request, slug):
         .order_by("-pub_date")
         .prefetch_related("author")
     )
-    return render_news(request, objects, "news/%s_index.html" % slug)
+    return render_news(request, objects, f"news/{slug}_index.html")
 
 
 def render_news(request, objects, template):
diff --git a/phonedb/forms.py b/phonedb/forms.py
index a801e7bd..69b4ef2e 100644
--- a/phonedb/forms.py
+++ b/phonedb/forms.py
@@ -36,7 +36,7 @@ def __init__(self, *args, **kwargs):
                     _('%(description)s [<a href="%(url)s">Link</a>]')
                     % {
                         "description": f.get_description(),
-                        "url": "/phones/search/%s/" % f.name,
+                        "url": f"/phones/search/{f.name}/",
                     },
                 ),
             )
diff --git a/phonedb/models.py b/phonedb/models.py
index 4d03d323..33114a95 100644
--- a/phonedb/models.py
+++ b/phonedb/models.py
@@ -173,7 +173,7 @@ def get_related_sites(self):
         name = self.__str__().replace(" ", "_").replace("-", "_")
         result.append(
             {
-                "url": "https://wikipedia.org/wiki/%s" % name,
+                "url": f"https://wikipedia.org/wiki/{name}",
                 "name": "Wikipedia",
             },
         )
@@ -195,8 +195,7 @@ def get_related_sites(self):
                 name = name[:-1] + "_fold"
             result.append(
                 {
-                    "url": "http://www.developer.nokia.com/Devices/Device_specifications/%s/"
-                    % name,
+                    "url": f"http://www.developer.nokia.com/Devices/Device_specifications/{name}/",
                     "name": "Nokia Developer",
                 },
             )
diff --git a/phonedb/views.py b/phonedb/views.py
index 7ad4ac09..cf5b6b28 100644
--- a/phonedb/views.py
+++ b/phonedb/views.py
@@ -28,7 +28,7 @@
 
 
 def get_chart_url(force=False):
-    cache_key = "phonedb-chart-url-%s" % settings.LANGUAGE_CODE
+    cache_key = f"phonedb-chart-url-{settings.LANGUAGE_CODE}"
     url = cache.get(cache_key)
     if url is not None and not force:
         return url
@@ -195,12 +195,12 @@ def search(request, featurename=None):
         if len(features) > 0:
             phones = phones.filter(connection__isnull=False)
             for feature in features:
-                urlparams.append("feature=%s" % feature)
+                urlparams.append(f"feature={feature}")
                 phones = phones.filter(features__name=feature)
 
         # Filter for query string
         if query:
-            urlparams.append("q=%s" % query)
+            urlparams.append(f"q={query}")
             query = query.strip()
             for part in query.split():
                 phones = phones.filter(
@@ -501,7 +501,7 @@ def create_wammu(request):  # noqa: C901
 
     features = []
     for feature in Feature.objects.all():
-        key = "fts[%s]" % feature.name
+        key = f"fts[{feature.name}]"
         if key in request.POST and request.POST[key] == "1":
             features.append(feature)
 
diff --git a/pyproject.toml b/pyproject.toml
index 666e1bb8..f070446a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -2,6 +2,9 @@
 profile = "black"
 
 [tool.ruff]
+output-format = "github"
+
+[tool.ruff.lint]
 extend-safe-fixes = [
   "D",
   "TCH",
@@ -44,10 +47,11 @@ ignore = [
   "EM101",
   "PT",
   "PTH",
-  "ANN"
+  "ANN",
+  "COM812",
+  "ISC001"
 ]
-output-format = "github"
 select = ["ALL"]
 
-[tool.ruff.mccabe]
+[tool.ruff.lint.mccabe]
 max-complexity = 16
diff --git a/screenshots/thumbs.py b/screenshots/thumbs.py
index 39aeaf10..0d154980 100644
--- a/screenshots/thumbs.py
+++ b/screenshots/thumbs.py
@@ -96,8 +96,9 @@ def save(self, name, content, save=True):
 
                 thumb_name_ = self.storage.save(thumb_name, thumb_content)
 
-                if not thumb_name == thumb_name_:
-                    raise ValueError("There is already a file named %s" % thumb_name)
+                if thumb_name != thumb_name_:
+                    msg = f"There is already a file named {thumb_name}"
+                    raise ValueError(msg)
 
     def delete(self, save=True):
         name = self.name
diff --git a/screenshots/views.py b/screenshots/views.py
index af7f6b26..25eae878 100644
--- a/screenshots/views.py
+++ b/screenshots/views.py
@@ -15,7 +15,7 @@ def index(request):
 def category(request, slug):
     category = get_object_or_404(Category, slug=slug)
     objects = Screenshot.objects.filter(categories=category).order_by("title")
-    return render_screenshots(request, objects, "screenshots/%s_index.html" % slug)
+    return render_screenshots(request, objects, f"screenshots/{slug}_index.html")
 
 
 def render_screenshots(request, objects, template):
diff --git a/settings.py b/settings.py
index 5ef2959b..aba25fbc 100644
--- a/settings.py
+++ b/settings.py
@@ -49,7 +49,7 @@
     ("sk", "Slovenčina"),
 )
 
-LOCALE_PATHS = ("%s/locale" % WEB_ROOT,)
+LOCALE_PATHS = (f"{WEB_ROOT}/locale",)
 
 # If you set this to False, Django will make some optimizations so as not
 # to load the internationalization machinery.
@@ -59,9 +59,9 @@
 # calendars according to the current locale
 
 # Absolute filesystem path to the directory that will hold user-uploaded files.
-MEDIA_ROOT = "%s/media/" % WEB_ROOT
+MEDIA_ROOT = f"{WEB_ROOT}/media/"
 
-HTML_ROOT = "%s/html/" % WEB_ROOT
+HTML_ROOT = f"{WEB_ROOT}/html/"
 
 # URL that handles the media served from MEDIA_ROOT. Make sure to use a
 # trailing slash.
diff --git a/tools/templatetags/encoding.py b/tools/templatetags/encoding.py
index 438eb573..77b9c2ed 100644
--- a/tools/templatetags/encoding.py
+++ b/tools/templatetags/encoding.py
@@ -22,9 +22,11 @@ def base64(value):
 @register.filter
 def xpm2png(value):
     xpm = """/* XPM */
-static char * ala_xpm[] = {
-"%s"};""" % '",\n"'.join(
-        value,
+static char * ala_xpm[] = {{
+"{}"}};""".format(
+        '",\n"'.join(
+            value,
+        )
     )
     xpm = xpm.replace("None", "#ffffff").replace("Black", "#000000")
     io = StringIO(xpm)
@@ -41,6 +43,6 @@ def xpm2png(value):
 def wrap(value):
     ret = ""
     while len(value) > 0:
-        ret += "%s\n" % value[:32]
+        ret += f"{value[:32]}\n"
         value = value[32:]
     return ret
diff --git a/urls.py b/urls.py
index dbe23f7b..1a370a74 100644
--- a/urls.py
+++ b/urls.py
@@ -48,39 +48,39 @@ class PagesSitemap(Sitemap):
 
     def items(self):
         return [
-            ("/", "%s/index.html" % settings.HTML_ROOT, 1),
-            ("/gammu/", "%s/gammu.html" % settings.HTML_ROOT, 1),
-            ("/libgammu/", "%s/libgammu.html" % settings.HTML_ROOT, 1),
-            ("/wammu/", "%s/wammu.html" % settings.HTML_ROOT, 1),
-            ("/smsd/", "%s/smsd.html" % settings.HTML_ROOT, 1),
-            ("/python-gammu/", "%s/python-gammu.html" % settings.HTML_ROOT, 1),
-            ("/authors/", "%s/authors.html" % settings.HTML_ROOT, 0.9),
-            ("/license/", "%s/libgammu.html" % settings.HTML_ROOT, 0.9),
-            ("/donate/", "%s/donate.html" % settings.HTML_ROOT, 0.3),
-            ("/s60/", "%s/s60.html" % settings.HTML_ROOT, 0.3),
-            ("/support/", "%s/support/index.html" % settings.HTML_ROOT, 0.9),
-            ("/support/bugs/", "%s/support/bugs.html" % settings.HTML_ROOT, 0.9),
-            ("/support/lists/", "%s/support/lists.html" % settings.HTML_ROOT, 0.9),
-            ("/support/online/", "%s/support/online.html" % settings.HTML_ROOT, 0.9),
-            ("/support/buy/", "%s/support/buy.html" % settings.HTML_ROOT, 0.9),
-            ("/contribute/", "%s/contribute/index.html" % settings.HTML_ROOT, 0.9),
-            ("/contribute/code/", "%s/contribute/code.html" % settings.HTML_ROOT, 0.9),
+            ("/", f"{settings.HTML_ROOT}/index.html", 1),
+            ("/gammu/", f"{settings.HTML_ROOT}/gammu.html", 1),
+            ("/libgammu/", f"{settings.HTML_ROOT}/libgammu.html", 1),
+            ("/wammu/", f"{settings.HTML_ROOT}/wammu.html", 1),
+            ("/smsd/", f"{settings.HTML_ROOT}/smsd.html", 1),
+            ("/python-gammu/", f"{settings.HTML_ROOT}/python-gammu.html", 1),
+            ("/authors/", f"{settings.HTML_ROOT}/authors.html", 0.9),
+            ("/license/", f"{settings.HTML_ROOT}/libgammu.html", 0.9),
+            ("/donate/", f"{settings.HTML_ROOT}/donate.html", 0.3),
+            ("/s60/", f"{settings.HTML_ROOT}/s60.html", 0.3),
+            ("/support/", f"{settings.HTML_ROOT}/support/index.html", 0.9),
+            ("/support/bugs/", f"{settings.HTML_ROOT}/support/bugs.html", 0.9),
+            ("/support/lists/", f"{settings.HTML_ROOT}/support/lists.html", 0.9),
+            ("/support/online/", f"{settings.HTML_ROOT}/support/online.html", 0.9),
+            ("/support/buy/", f"{settings.HTML_ROOT}/support/buy.html", 0.9),
+            ("/contribute/", f"{settings.HTML_ROOT}/contribute/index.html", 0.9),
+            ("/contribute/code/", f"{settings.HTML_ROOT}/contribute/code.html", 0.9),
             (
                 "/contribute/translate/",
-                "%s/contribute/translate.html" % settings.HTML_ROOT,
+                f"{settings.HTML_ROOT}/contribute/translate.html",
                 0.9,
             ),
             (
                 "/contribute/publicity/",
-                "%s/contribute/publicity.html" % settings.HTML_ROOT,
+                f"{settings.HTML_ROOT}/contribute/publicity.html",
                 0.9,
             ),
             (
                 "/contribute/wanted/",
-                "%s/contribute/wanted.html" % settings.HTML_ROOT,
+                f"{settings.HTML_ROOT}/contribute/wanted.html",
                 0.9,
             ),
-            ("/docs/", "%s/docs/index.html" % settings.HTML_ROOT, 0.9),
+            ("/docs/", f"{settings.HTML_ROOT}/docs/index.html", 0.9),
             ("/screenshots/", None, 0.8),
             ("/downloads/gammu/", None, 0.7),
             ("/downloads/python-gammu/", None, 0.7),
diff --git a/wammu/context_processors.py b/wammu/context_processors.py
index 7ffcd1bf..b18187e2 100644
--- a/wammu/context_processors.py
+++ b/wammu/context_processors.py
@@ -17,43 +17,43 @@ def translations(request):
 
     if lang != "cs":
         langs.append(
-            {"url": "https://cs.wammu.eu%s" % path, "name": "Česky", "code": "cs"},
+            {"url": f"https://cs.wammu.eu{path}", "name": "Česky", "code": "cs"},
         )
 
     if lang != "en":
         langs.append(
-            {"url": "https://wammu.eu%s" % path, "name": "English", "code": "en"},
+            {"url": f"https://wammu.eu{path}", "name": "English", "code": "en"},
         )
 
     if lang != "es":
         langs.append(
-            {"url": "https://es.wammu.eu%s" % path, "name": "Español", "code": "es"},
+            {"url": f"https://es.wammu.eu{path}", "name": "Español", "code": "es"},
         )
 
     if lang != "de":
         langs.append(
-            {"url": "https://de.wammu.eu%s" % path, "name": "Deutsch", "code": "de"},
+            {"url": f"https://de.wammu.eu{path}", "name": "Deutsch", "code": "de"},
         )
 
     if lang != "ru":
         langs.append(
-            {"url": "https://ru.wammu.eu%s" % path, "name": "Русский", "code": "ru"},
+            {"url": f"https://ru.wammu.eu{path}", "name": "Русский", "code": "ru"},
         )
 
     if lang != "sk":
         langs.append(
-            {"url": "https://sk.wammu.eu%s" % path, "name": "Slovenčina", "code": "sk"},
+            {"url": f"https://sk.wammu.eu{path}", "name": "Slovenčina", "code": "sk"},
         )
 
     if lang != "fr":
         langs.append(
-            {"url": "https://fr.wammu.eu%s" % path, "name": "Français", "code": "fr"},
+            {"url": f"https://fr.wammu.eu{path}", "name": "Français", "code": "fr"},
         )
 
     if lang != "pt-br":
         langs.append(
             {
-                "url": "https://pt-br.wammu.eu%s" % path,
+                "url": f"https://pt-br.wammu.eu{path}",
                 "name": "Português brasileiro",
                 "code": "pt-BR",
             },