diff --git a/Userland/Utilities/dd.cpp b/Userland/Utilities/dd.cpp
index 6c472a9eaf..5f9b149097 100644
--- a/Userland/Utilities/dd.cpp
+++ b/Userland/Utilities/dd.cpp
@@ -4,11 +4,11 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/Optional.h>
 #include <AK/Vector.h>
 #include <LibMain/Main.h>
-#include <ctype.h>
 #include <fcntl.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -72,7 +72,7 @@ static int handle_size_arguments(size_t& numeric_value, StringView argument)
 
     unsigned suffix_multiplier = 1;
     auto suffix = value[value.length() - 1];
-    switch (tolower(suffix)) {
+    switch (to_ascii_lowercase(suffix)) {
     case 'k':
         suffix_multiplier = KiB;
         value = value.substring_view(0, value.length() - 1);
diff --git a/Userland/Utilities/hexdump.cpp b/Userland/Utilities/hexdump.cpp
index 67e4f20b2c..c11c46a3a4 100644
--- a/Userland/Utilities/hexdump.cpp
+++ b/Userland/Utilities/hexdump.cpp
@@ -6,6 +6,7 @@
  */
 
 #include <AK/Array.h>
+#include <AK/CharacterTypes.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/File.h>
 #include <LibCore/System.h>
@@ -56,7 +57,7 @@ ErrorOr<int> serenity_main(Main::Arguments args)
         out("  |");
 
         for (auto const& byte : line) {
-            if (isprint(byte))
+            if (is_ascii_printable(byte))
                 putchar(byte);
             else
                 putchar('.');
diff --git a/Userland/Utilities/kill.cpp b/Userland/Utilities/kill.cpp
index ec580a92ee..da78e72e36 100644
--- a/Userland/Utilities/kill.cpp
+++ b/Userland/Utilities/kill.cpp
@@ -4,10 +4,10 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/Optional.h>
 #include <LibCore/System.h>
 #include <LibMain/Main.h>
-#include <ctype.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -48,7 +48,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
         Optional<unsigned> number;
 
-        if (isalpha(strings[1][1])) {
+        if (is_ascii_alpha(strings[1][1])) {
             int value = getsignalbyname(&strings[1][1]);
             if (value >= 0 && value < NSIG)
                 number = value;
diff --git a/Userland/Utilities/killall.cpp b/Userland/Utilities/killall.cpp
index a2e57d1f27..80668b1165 100644
--- a/Userland/Utilities/killall.cpp
+++ b/Userland/Utilities/killall.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <LibCore/ProcessStatisticsReader.h>
 #include <LibCore/System.h>
@@ -48,7 +49,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
         Optional<unsigned> number;
 
-        if (isalpha(arguments.argv[1][1])) {
+        if (is_ascii_alpha(arguments.argv[1][1])) {
             int value = getsignalbyname(&arguments.argv[1][1]);
             if (value >= 0 && value < NSIG)
                 number = value;
diff --git a/Userland/Utilities/ls.cpp b/Userland/Utilities/ls.cpp
index 2dc62560a5..d33788dafe 100644
--- a/Userland/Utilities/ls.cpp
+++ b/Userland/Utilities/ls.cpp
@@ -211,7 +211,7 @@ static int print_escaped(StringView name)
     }
 
     for (auto c : name) {
-        if (isprint(c)) {
+        if (is_ascii_printable(c)) {
             putchar(c);
             printed++;
         } else {
diff --git a/Userland/Utilities/lsof.cpp b/Userland/Utilities/lsof.cpp
index db2a7fcd3c..53f9772443 100644
--- a/Userland/Utilities/lsof.cpp
+++ b/Userland/Utilities/lsof.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/GenericLexer.h>
 #include <AK/JsonArray.h>
@@ -38,8 +39,8 @@ static bool parse_name(StringView name, OpenFile& file)
         return true;
     } else {
         file.type = component1;
-        auto component2 = lexer.consume_while([](char c) { return isprint(c) && c != '('; });
-        lexer.ignore_while(isspace);
+        auto component2 = lexer.consume_while([](char c) { return is_ascii_printable(c) && c != '('; });
+        lexer.ignore_while(is_ascii_space);
         file.name = component2;
 
         if (lexer.tell_remaining() == 0) {
diff --git a/Userland/Utilities/pro.cpp b/Userland/Utilities/pro.cpp
index 157ea98f1c..05314e08e0 100644
--- a/Userland/Utilities/pro.cpp
+++ b/Userland/Utilities/pro.cpp
@@ -6,6 +6,7 @@
  */
 
 #include <AK/Base64.h>
+#include <AK/CharacterTypes.h>
 #include <AK/GenericLexer.h>
 #include <AK/LexicalPath.h>
 #include <AK/MaybeOwned.h>
@@ -30,7 +31,7 @@ public:
     {
         GenericLexer lexer(value);
 
-        lexer.ignore_while(isspace);
+        lexer.ignore_while(is_ascii_space);
 
         if (lexer.consume_specific("inline")) {
             m_kind = Kind::Inline;
@@ -42,7 +43,7 @@ public:
         if (lexer.consume_specific("attachment")) {
             m_kind = Kind::Attachment;
             if (lexer.consume_specific(";")) {
-                lexer.ignore_while(isspace);
+                lexer.ignore_while(is_ascii_space);
                 if (lexer.consume_specific("filename=")) {
                     // RFC 2183: "A short (length <= 78 characters)
                     //            parameter value containing only non-`tspecials' characters SHOULD be
@@ -64,7 +65,7 @@ public:
         if (lexer.consume_specific("form-data")) {
             m_kind = Kind::FormData;
             while (lexer.consume_specific(";")) {
-                lexer.ignore_while(isspace);
+                lexer.ignore_while(is_ascii_space);
                 if (lexer.consume_specific("name=")) {
                     m_name = lexer.consume_quoted_string();
                 } else if (lexer.consume_specific("filename=")) {
diff --git a/Userland/Utilities/readelf.cpp b/Userland/Utilities/readelf.cpp
index 6ae9684cb0..97cbabb408 100644
--- a/Userland/Utilities/readelf.cpp
+++ b/Userland/Utilities/readelf.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/LexicalPath.h>
 #include <AK/StringBuilder.h>
@@ -338,7 +339,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
         out("  Magic:                             ");
         for (char i : StringView { header.e_ident, sizeof(header.e_ident) }) {
-            if (isprint(i)) {
+            if (is_ascii_printable(i)) {
                 out("{:c} ", i);
             } else {
                 out("{:02x} ", i);
diff --git a/Userland/Utilities/sort.cpp b/Userland/Utilities/sort.cpp
index 987f101152..6894ba3aae 100644
--- a/Userland/Utilities/sort.cpp
+++ b/Userland/Utilities/sort.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/HashMap.h>
 #include <AK/QuickSort.h>
@@ -13,7 +14,6 @@
 #include <LibCore/File.h>
 #include <LibCore/System.h>
 #include <LibMain/Main.h>
-#include <ctype.h>
 
 struct Line {
     StringView key;
@@ -74,7 +74,7 @@ static ErrorOr<void> load_file(Options options, StringView filename, Vector<Line
         if (options.key_field != 0) {
             auto split = (options.separator[0])
                 ? line.split_view(options.separator[0])
-                : line.split_view(isspace);
+                : line.split_view(is_ascii_space);
             if (options.key_field - 1 >= split.size()) {
                 key = ""sv;
             } else {
diff --git a/Userland/Utilities/stty.cpp b/Userland/Utilities/stty.cpp
index a943855319..7e277f82e3 100644
--- a/Userland/Utilities/stty.cpp
+++ b/Userland/Utilities/stty.cpp
@@ -7,6 +7,7 @@
 
 #define __USE_MISC
 #define TTYDEFCHARS
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/Optional.h>
 #include <AK/Result.h>
@@ -265,9 +266,9 @@ Result<void, int> apply_stty_readable_modes(StringView mode_string, termios& t)
     auto parse_hex = [&](StringView v) {
         tcflag_t ret = 0;
         for (auto c : v) {
-            c = tolower(c);
+            c = to_ascii_lowercase(c);
             ret *= 16;
-            if (isdigit(c)) {
+            if (is_ascii_digit(c)) {
                 ret += c - '0';
             } else {
                 VERIFY(c >= 'a' && c <= 'f');
@@ -310,8 +311,8 @@ Result<void, int> apply_modes(size_t parameter_count, char** raw_parameters, ter
     auto looks_like_stty_readable = [&](size_t idx) {
         bool contains_colon = false;
         for (auto c : parameters[idx]) {
-            c = tolower(c);
-            if (!isdigit(c) && !(c >= 'a' && c <= 'f') && c != ':')
+            c = to_ascii_lowercase(c);
+            if (!is_ascii_digit(c) && !(c >= 'a' && c <= 'f') && c != ':')
                 return false;
             if (c == ':')
                 contains_colon = true;
@@ -326,7 +327,7 @@ Result<void, int> apply_modes(size_t parameter_count, char** raw_parameters, ter
             // We should add the _POSIX_VDISABLE macro.
             return 0;
         } else if (parameters[idx][0] == '^' && parameters[idx].length() == 2) {
-            return toupper(parameters[idx][1]) - 0x40;
+            return to_ascii_uppercase(parameters[idx][1]) - 0x40;
         } else if (parameters[idx].starts_with("0x"sv)) {
             cc_t value = 0;
             if (parameters[idx].length() == 2) {
@@ -334,12 +335,12 @@ Result<void, int> apply_modes(size_t parameter_count, char** raw_parameters, ter
                 return {};
             }
             for (size_t i = 2; i < parameters[idx].length(); ++i) {
-                char ch = tolower(parameters[idx][i]);
-                if (!isdigit(ch) && !(ch >= 'a' && ch <= 'f')) {
+                char ch = to_ascii_lowercase(parameters[idx][i]);
+                if (!is_ascii_digit(ch) && !(ch >= 'a' && ch <= 'f')) {
                     warnln("Invalid hexadecimal character code {}", parameters[idx]);
                     return {};
                 }
-                value = 16 * value + (isdigit(ch)) ? (ch - '0') : (ch - 'a');
+                value = 16 * value + (is_ascii_digit(ch) ? (ch - '0') : (ch - 'a'));
             }
             return value;
         } else if (parameters[idx].starts_with("0"sv)) {
@@ -353,7 +354,7 @@ Result<void, int> apply_modes(size_t parameter_count, char** raw_parameters, ter
                 value = 8 * value + (ch - '0');
             }
             return value;
-        } else if (isdigit(parameters[idx][0])) {
+        } else if (is_ascii_digit(parameters[idx][0])) {
             auto maybe_value = parameters[idx].to_uint<cc_t>();
             if (!maybe_value.has_value()) {
                 warnln("Invalid decimal character code {}", parameters[idx]);
@@ -449,7 +450,7 @@ Result<void, int> apply_modes(size_t parameter_count, char** raw_parameters, ter
             auto maybe_error = apply_stty_readable_modes(parameters[parameter_idx], t);
             if (maybe_error.is_error())
                 return maybe_error.error();
-        } else if (isdigit(parameters[parameter_idx][0])) {
+        } else if (is_ascii_digit(parameters[parameter_idx][0])) {
             auto new_baud = parse_baud(parameter_idx);
             if (!new_baud.has_value()) {
                 warnln("Invalid baud rate {}", parameters[parameter_idx]);
diff --git a/Userland/Utilities/touch.cpp b/Userland/Utilities/touch.cpp
index 8652b4b611..2f68d206fe 100644
--- a/Userland/Utilities/touch.cpp
+++ b/Userland/Utilities/touch.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/CheckedFormatString.h>
 #include <AK/GenericLexer.h>
 #include <AK/Time.h>
@@ -60,7 +61,7 @@ static void parse_time(StringView input_time, timespec& atime, timespec& mtime)
             err("invalid time format '{}'", input_time);
     };
 
-    while (!lexer.is_eof() && lexer.next_is(isdigit))
+    while (!lexer.is_eof() && lexer.next_is(is_ascii_digit))
         lex_number();
     if (parameters.size() > 6)
         err("invalid time format '{}' -- too many parameters", input_time);
@@ -131,7 +132,7 @@ static void parse_datetime(StringView input_datetime, timespec& atime, timespec&
     millisecond = 0;
     if (!lexer.is_eof()) {
         if (lexer.consume_specific(',') || lexer.consume_specific('.')) {
-            auto fractional_second = lexer.consume_while(isdigit);
+            auto fractional_second = lexer.consume_while(is_ascii_digit);
             if (fractional_second.is_empty())
                 err("invalid datetime format '{}' -- expected floating seconds", input_datetime);
             for (u8 i = 0; i < 3 && i < fractional_second.length(); ++i) {
diff --git a/Userland/Utilities/tr.cpp b/Userland/Utilities/tr.cpp
index 17d80c4adf..2c82d994d5 100644
--- a/Userland/Utilities/tr.cpp
+++ b/Userland/Utilities/tr.cpp
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/GenericLexer.h>
 #include <AK/Optional.h>
@@ -34,29 +35,29 @@ static ErrorOr<DeprecatedString> build_set(StringView specification)
 
     while (!lexer.is_eof()) {
         if (lexer.consume_specific("[:alnum:]"sv))
-            TRY(generate_character_class(isalnum, out));
+            TRY(generate_character_class(is_ascii_alphanumeric, out));
         else if (lexer.consume_specific("[:blank:]"sv))
-            TRY(generate_character_class(isblank, out));
+            TRY(generate_character_class(is_ascii_blank, out));
         else if (lexer.consume_specific("[:digit:]"sv))
-            TRY(generate_character_class(isdigit, out));
+            TRY(generate_character_class(is_ascii_digit, out));
         else if (lexer.consume_specific("[:lower:]"sv))
-            TRY(generate_character_class(islower, out));
+            TRY(generate_character_class(is_ascii_lower_alpha, out));
         else if (lexer.consume_specific("[:punct:]"sv))
-            TRY(generate_character_class(ispunct, out));
+            TRY(generate_character_class(is_ascii_punctuation, out));
         else if (lexer.consume_specific("[:upper:]"sv))
-            TRY(generate_character_class(isupper, out));
+            TRY(generate_character_class(is_ascii_upper_alpha, out));
         else if (lexer.consume_specific("[:alpha:]"sv))
-            TRY(generate_character_class(isalpha, out));
+            TRY(generate_character_class(is_ascii_alpha, out));
         else if (lexer.consume_specific("[:cntrl:]"sv))
-            TRY(generate_character_class(iscntrl, out));
+            TRY(generate_character_class(is_ascii_control, out));
         else if (lexer.consume_specific("[:graph:]"sv))
-            TRY(generate_character_class(isgraph, out));
+            TRY(generate_character_class(is_ascii_graphical, out));
         else if (lexer.consume_specific("[:print:]"sv))
-            TRY(generate_character_class(isprint, out));
+            TRY(generate_character_class(is_ascii_printable, out));
         else if (lexer.consume_specific("[:space:]"sv))
-            TRY(generate_character_class(isspace, out));
+            TRY(generate_character_class(is_ascii_space, out));
         else if (lexer.consume_specific("[:xdigit:]"sv))
-            TRY(generate_character_class(isxdigit, out));
+            TRY(generate_character_class(is_ascii_hex_digit, out));
         else if (lexer.consume_specific("\\\\"sv))
             TRY(out.try_append('\\'));
         else if (lexer.consume_specific("\\a"sv))
diff --git a/Userland/Utilities/useradd.cpp b/Userland/Utilities/useradd.cpp
index 1bb89a444a..8f3e67b387 100644
--- a/Userland/Utilities/useradd.cpp
+++ b/Userland/Utilities/useradd.cpp
@@ -7,6 +7,7 @@
  */
 
 #include <AK/Base64.h>
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/Random.h>
 #include <LibCore/ArgsParser.h>
@@ -59,7 +60,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     }
 
     // Disallow names starting with _ and -
-    if (username[0] == '_' || username[0] == '-' || !isalpha(username[0])) {
+    if (username[0] == '_' || username[0] == '-' || !is_ascii_alpha(username[0])) {
         warnln("invalid username, {}", username);
         return 1;
     }
diff --git a/Userland/Utilities/wc.cpp b/Userland/Utilities/wc.cpp
index 87af538a7c..a0c296c9c0 100644
--- a/Userland/Utilities/wc.cpp
+++ b/Userland/Utilities/wc.cpp
@@ -5,6 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/CharacterTypes.h>
 #include <AK/DeprecatedString.h>
 #include <AK/Vector.h>
 #include <LibCore/ArgsParser.h>
@@ -58,7 +59,7 @@ static Count get_count(DeprecatedString const& file_specifier)
     bool start_a_new_word = true;
     for (int ch = fgetc(file_pointer); ch != EOF; ch = fgetc(file_pointer)) {
         count.bytes++;
-        if (isspace(ch)) {
+        if (is_ascii_space(ch)) {
             start_a_new_word = true;
             if (ch == '\n')
                 count.lines++;