diff --git a/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.java b/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.java
deleted file mode 100644
index bc15f3f02..000000000
--- a/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.java
+++ /dev/null
@@ -1,70 +0,0 @@
-package org.schabi.newpipe.util;
-
-import android.content.Context;
-import android.content.SharedPreferences;
-
-import androidx.preference.PreferenceManager;
-
-import org.schabi.newpipe.R;
-
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-public final class FilenameUtils {
-    private static final String CHARSET_MOST_SPECIAL = "[\\n\\r|?*<\":\\\\>/']+";
-    private static final String CHARSET_ONLY_LETTERS_AND_DIGITS = "[^\\w\\d]+";
-
-    private FilenameUtils() { }
-
-    /**
-     * #143 #44 #42 #22: make sure that the filename does not contain illegal chars.
-     *
-     * @param context the context to retrieve strings and preferences from
-     * @param title   the title to create a filename from
-     * @return the filename
-     */
-    public static String createFilename(final Context context, final String title) {
-        final SharedPreferences sharedPreferences = PreferenceManager
-                .getDefaultSharedPreferences(context);
-
-        final String charsetLd = context.getString(R.string.charset_letters_and_digits_value);
-        final String charsetMs = context.getString(R.string.charset_most_special_value);
-        final String defaultCharset = context.getString(R.string.default_file_charset_value);
-
-        final String replacementChar = sharedPreferences.getString(
-                context.getString(R.string.settings_file_replacement_character_key), "_");
-        String selectedCharset = sharedPreferences.getString(
-                context.getString(R.string.settings_file_charset_key), null);
-
-        final String charset;
-
-        if (selectedCharset == null || selectedCharset.isEmpty()) {
-            selectedCharset = defaultCharset;
-        }
-
-        if (selectedCharset.equals(charsetLd)) {
-            charset = CHARSET_ONLY_LETTERS_AND_DIGITS;
-        } else if (selectedCharset.equals(charsetMs)) {
-            charset = CHARSET_MOST_SPECIAL;
-        } else {
-            charset = selectedCharset; // Is the user using a custom charset?
-        }
-
-        final Pattern pattern = Pattern.compile(charset);
-
-        return createFilename(title, pattern, Matcher.quoteReplacement(replacementChar));
-    }
-
-    /**
-     * Create a valid filename.
-     *
-     * @param title             the title to create a filename from
-     * @param invalidCharacters patter matching invalid characters
-     * @param replacementChar   the replacement
-     * @return the filename
-     */
-    private static String createFilename(final String title, final Pattern invalidCharacters,
-                                         final String replacementChar) {
-        return title.replaceAll(invalidCharacters.pattern(), replacementChar);
-    }
-}
diff --git a/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.kt b/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.kt
new file mode 100644
index 000000000..bfa50beef
--- /dev/null
+++ b/app/src/main/java/org/schabi/newpipe/util/FilenameUtils.kt
@@ -0,0 +1,64 @@
+/*
+ * SPDX-FileCopyrightText: 2017-2025 NewPipe contributors <https://newpipe.net>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package org.schabi.newpipe.util
+
+import android.content.Context
+import androidx.preference.PreferenceManager
+import org.schabi.newpipe.R
+import org.schabi.newpipe.ktx.getStringSafe
+import java.util.regex.Matcher
+
+object FilenameUtils {
+    private const val CHARSET_MOST_SPECIAL = "[\\n\\r|?*<\":\\\\>/']+"
+    private const val CHARSET_ONLY_LETTERS_AND_DIGITS = "[^\\w\\d]+"
+
+    /**
+     * #143 #44 #42 #22: make sure that the filename does not contain illegal chars.
+     *
+     * @param context the context to retrieve strings and preferences from
+     * @param title the title to create a filename from
+     * @return the filename
+     */
+    @JvmStatic
+    fun createFilename(context: Context, title: String): String {
+        val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context)
+
+        val charsetLd = context.getString(R.string.charset_letters_and_digits_value)
+        val charsetMs = context.getString(R.string.charset_most_special_value)
+        val defaultCharset = context.getString(R.string.default_file_charset_value)
+
+        val replacementChar = sharedPreferences.getStringSafe(
+            context.getString(R.string.settings_file_replacement_character_key), "_"
+        )
+        val selectedCharset = sharedPreferences.getStringSafe(
+            context.getString(R.string.settings_file_charset_key), ""
+        ).ifEmpty { defaultCharset }
+
+        val charset = when (selectedCharset) {
+            charsetLd -> CHARSET_ONLY_LETTERS_AND_DIGITS
+            charsetMs -> CHARSET_MOST_SPECIAL
+            else -> selectedCharset // Is the user using a custom charset?
+        }
+
+        return createFilename(title, charset, Matcher.quoteReplacement(replacementChar))
+    }
+
+    /**
+     * Create a valid filename.
+     *
+     * @param title the title to create a filename from
+     * @param invalidCharacters patter matching invalid characters
+     * @param replacementChar the replacement
+     * @return the filename
+     */
+    private fun createFilename(
+        title: String,
+        invalidCharacters: String,
+        replacementChar: String
+    ): String {
+        return title.replace(invalidCharacters.toRegex(), replacementChar)
+    }
+}