diff --git a/app/src/main/java/com/trianguloy/urlchecker/modules/list/PatternModule.java b/app/src/main/java/com/trianguloy/urlchecker/modules/list/PatternModule.java
index 59891f1..614743e 100644
--- a/app/src/main/java/com/trianguloy/urlchecker/modules/list/PatternModule.java
+++ b/app/src/main/java/com/trianguloy/urlchecker/modules/list/PatternModule.java
@@ -1,5 +1,7 @@
 package com.trianguloy.urlchecker.modules.list;
 
+import android.annotation.TargetApi;
+import android.os.Build;
 import android.view.View;
 import android.widget.Button;
 import android.widget.LinearLayout;
@@ -24,6 +26,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
 import java.util.regex.Pattern;
+import java.util.regex.Matcher;
 
 /**
  * This module checks for patterns characters in the url
@@ -122,7 +125,7 @@ class PatternDialog extends AModuleDialog {
 
                 // get regex (must exists)
                 if (!data.has("regex")) continue;
-                var regex = data.getString("regex");
+                Pattern regex = Pattern.compile(data.getString("regex"));
 
                 // applied?
                 message.applied = urlData.getData(APPLIED + pattern) != null;
@@ -130,7 +133,7 @@ class PatternDialog extends AModuleDialog {
                 // check matches
                 // if 'regexp' matches, the pattern can match
                 // if 'regexp' doesn't match, the patter doesn't match
-                var matches = Pattern.compile(regex).matcher(url).find();
+                var matches = regex.matcher(url).find();
                 if (matches && data.has("excludeRegex")) {
                     // if 'excludeRegex' doesn't exist, the pattern can match
                     // if 'excludeRegex' matches, the pattern doesn't matches
@@ -158,7 +161,7 @@ class PatternDialog extends AModuleDialog {
 
                     if (replacement != null) {
                         // replace url
-                        message.newUrl = url.replaceAll(regex, replacement);
+                        message.newUrl = replaceAll(url, regex, replacement);
 
                         // automatic? apply
                         if (data.optBoolean("automatic")) {
@@ -225,4 +228,100 @@ class PatternDialog extends AModuleDialog {
             this.pattern = pattern;
         }
     }
+
+    /**
+     * On Android 10 and under, optional groups may yield a "null" in the replacement output instead of an empty string.
+     * Therefore, we just copy the implementation from newer versions
+     * https://github.com/TrianguloY/UrlChecker/issues/237
+     */
+    private static String replaceAll(String text, Pattern pattern, String replacement) {
+        // Copied from https://android.googlesource.com/platform/libcore/+/refs/heads/android13-release/ojluni/src/main/java/java/util/regex/Matcher.java#837
+        Matcher matcher = pattern.matcher(text);
+        boolean result = matcher.find();
+        if (result) {
+            StringBuffer sb = new StringBuffer();
+            int appendPos = 0;
+            do {
+                appendPos = appendReplacement(text, matcher, sb, replacement, appendPos);
+                result = matcher.find();
+            } while (result);
+            appendTail(text, sb, appendPos);
+            return sb.toString();
+        }
+        return text.toString();
+    }
+
+    private static int appendReplacement(String text, Matcher matcher, StringBuffer sb, String replacement, int appendPos) {
+        // Copied from https://android.googlesource.com/platform/libcore/+/refs/heads/android13-release/ojluni/src/main/java/java/util/regex/Matcher.java#714
+        sb.append(text.substring(appendPos, matcher.start()));
+        appendEvaluated(matcher, sb, replacement);
+        appendPos = matcher.end();
+
+        return appendPos;
+    }
+
+    @TargetApi(Build.VERSION_CODES.O)
+    private static void appendEvaluated(Matcher matcher, StringBuffer buffer, String s) {
+        // Copied from https://android.googlesource.com/platform/libcore/+/refs/heads/android13-release/ojluni/src/main/java/java/util/regex/Matcher.java#731
+        boolean escape = false;
+        boolean dollar = false;
+        boolean escapeNamedGroup = false;
+        int escapeNamedGroupStart = -1;
+
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            if (c == '\\' && !escape) {
+                escape = true;
+            } else if (c == '$' && !escape) {
+                dollar = true;
+            } else if (c >= '0' && c <= '9' && dollar && !escapeNamedGroup) {
+                String groupValue = matcher.group(c - '0');
+                if (groupValue != null) {
+                    buffer.append(groupValue);
+                }
+                dollar = false;
+            } else if (c == '{' && dollar) {
+                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
+                    throw new IllegalArgumentException("your android version does not support named-capturing groups");
+                }
+                escapeNamedGroup = true;
+                escapeNamedGroupStart = i;
+            } else if (c == '}' && dollar && escapeNamedGroup) {
+                String groupValue = matcher.group(s.substring(escapeNamedGroupStart + 1, i));
+                if (groupValue != null) {
+                    buffer.append(groupValue);
+                }
+                dollar = false;
+                escapeNamedGroup = false;
+            } else if (c != '}' && dollar && escapeNamedGroup) {
+                continue;
+            } else {
+                buffer.append(c);
+                dollar = false;
+                escape = false;
+                escapeNamedGroup = false;
+            }
+        }
+
+        if (escape) {
+            throw new IllegalArgumentException("character to be escaped is missing");
+        }
+
+        if (dollar) {
+            throw new IllegalArgumentException("Illegal group reference: group index is missing");
+        }
+
+        if (escapeNamedGroup) {
+            throw new IllegalArgumentException("Missing ending brace '}' from replacement string");
+        }
+    }
+
+    private static StringBuffer appendTail(String text, StringBuffer sb, int appendPos) {
+        // Copied from https://android.googlesource.com/platform/libcore/+/refs/heads/android13-release/ojluni/src/main/java/java/util/regex/Matcher.java#796
+        int to = text.length();
+        if (appendPos < to) {
+            sb.append(text.substring(appendPos, to));
+        }
+        return sb;
+    }
 }