diff --git a/src/core/wee-string.c b/src/core/wee-string.c
index 376903767..29c181bd0 100644
--- a/src/core/wee-string.c
+++ b/src/core/wee-string.c
@@ -31,6 +31,7 @@
 #include <wctype.h>
 #include <regex.h>
 #include <wchar.h>
+#include <stdint.h>
 
 #ifdef HAVE_ICONV
 #include <iconv.h>
@@ -47,11 +48,17 @@
 #include "weechat.h"
 #include "wee-string.h"
 #include "wee-config.h"
+#include "wee-hashtable.h"
 #include "wee-utf8.h"
 #include "../gui/gui-color.h"
 #include "../plugins/plugin.h"
 
 
+typedef uint32_t string_shared_count_t;
+
+struct t_hashtable *string_hashtable_shared = NULL;
+
+
 /*
  * Defines a "strndup" function for systems where this function does not exist
  * (FreeBSD and maybe others).
@@ -1052,6 +1059,9 @@ string_has_highlight_regex (const char *string, const char *regex)
 /*
  * Splits a string according to separators.
  *
+ * This function must not be called directly (call string_split or
+ * string_split_shared instead).
+ *
  * Examples:
  *   string_split ("abc de  fghi", " ", 0, 0, NULL)
  *     ==> array[0] = "abc"
@@ -1066,12 +1076,13 @@ string_has_highlight_regex (const char *string, const char *regex)
  */
 
 char **
-string_split (const char *string, const char *separators, int keep_eol,
-              int num_items_max, int *num_items)
+string_split_internal (const char *string, const char *separators, int keep_eol,
+                       int num_items_max, int *num_items, int shared)
 {
     int i, j, n_items;
     char *string2, **array;
     char *ptr, *ptr1, *ptr2;
+    const char *str_shared;
 
     if (num_items != NULL)
         *num_items = 0;
@@ -1141,13 +1152,18 @@ string_split (const char *string, const char *separators, int keep_eol,
             {
                 if (keep_eol)
                 {
-                    array[i] = strdup (ptr1);
+                    array[i] = (shared) ? (char *)string_shared_get (ptr1) : strdup (ptr1);
                     if (!array[i])
                     {
                         for (j = 0; j < n_items; j++)
                         {
                             if (array[j])
-                                free (array[j]);
+                            {
+                                if (shared)
+                                    string_shared_free (array[j]);
+                                else
+                                    free (array[j]);
+                            }
                         }
                         free (array);
                         free (string2);
@@ -1162,7 +1178,12 @@ string_split (const char *string, const char *separators, int keep_eol,
                         for (j = 0; j < n_items; j++)
                         {
                             if (array[j])
-                                free (array[j]);
+                            {
+                                if (shared)
+                                    string_shared_free (array[j]);
+                                else
+                                    free (array[j]);
+                            }
                         }
                         free (array);
                         free (string2);
@@ -1170,6 +1191,23 @@ string_split (const char *string, const char *separators, int keep_eol,
                     }
                     strncpy (array[i], ptr1, ptr2 - ptr1);
                     array[i][ptr2 - ptr1] = '\0';
+                    if (shared)
+                    {
+                        str_shared = string_shared_get (array[i]);
+                        if (!str_shared)
+                        {
+                            for (j = 0; j < n_items; j++)
+                            {
+                                if (array[j])
+                                    string_shared_free (array[j]);
+                            }
+                            free (array);
+                            free (string2);
+                            return NULL;
+                        }
+                        free (array[i]);
+                        array[i] = (char *)str_shared;
+                    }
                 }
                 ptr1 = ++ptr2;
             }
@@ -1189,6 +1227,35 @@ string_split (const char *string, const char *separators, int keep_eol,
     return array;
 }
 
+/*
+ * Splits a string according to separators.
+ *
+ * For full description, see function string_split_internal.
+ */
+
+char **
+string_split (const char *string, const char *separators, int keep_eol,
+              int num_items_max, int *num_items)
+{
+    return string_split_internal (string, separators, keep_eol,
+                                  num_items_max, num_items, 0);
+}
+
+/*
+ * Splits a string according to separators, and use shared strings for the
+ * strings in the array returned.
+ *
+ * For full description, see function string_split_internal.
+ */
+
+char **
+string_split_shared (const char *string, const char *separators, int keep_eol,
+                     int num_items_max, int *num_items)
+{
+    return string_split_internal (string, separators, keep_eol,
+                                  num_items_max, num_items, 1);
+}
+
 /*
  * Splits a string like the shell does for a command with arguments.
  *
@@ -1398,6 +1465,23 @@ string_free_split (char **split_string)
     }
 }
 
+/*
+ * Frees a split string (using shared strings).
+ */
+
+void
+string_free_split_shared (char **split_string)
+{
+    int i;
+
+    if (split_string)
+    {
+        for (i = 0; split_string[i]; i++)
+            string_shared_free (split_string[i]);
+        free (split_string);
+    }
+}
+
 /*
  * Builds a string with a split string.
  *
@@ -2193,3 +2277,163 @@ string_replace_with_callback (const char *string,
 
     return result;
 }
+
+/*
+ * Hashes a shared string.
+ * The string starts after the reference count, which is skipped.
+ *
+ * Returns the hash of the shared string (variant of djb2).
+ */
+
+unsigned long
+string_shared_hash_key (struct t_hashtable *hashtable,
+                        const void *key)
+{
+    /* make C compiler happy */
+    (void) hashtable;
+
+    return hashtable_hash_key_djb2 (((const char *)key) + sizeof (string_shared_count_t));
+}
+
+/*
+ * Compares two shared strings.
+ * Each string starts after the reference count, which is skipped.
+ *
+ * Returns:
+ *   < 0: key1 < key2
+ *     0: key1 == key2
+ *   > 0: key1 > key2
+ */
+
+int
+string_shared_keycmp (struct t_hashtable *hashtable,
+                      const void *key1, const void *key2)
+{
+    /* make C compiler happy */
+    (void) hashtable;
+
+    return strcmp (((const char *)key1) + sizeof (string_shared_count_t),
+                   ((const char *)key2) + sizeof (string_shared_count_t));
+}
+
+/*
+ * Frees a shared string.
+ */
+
+void
+string_shared_free_key (struct t_hashtable *hashtable,
+                        void *key, const void *value)
+{
+    /* make C compiler happy */
+    (void) hashtable;
+    (void) value;
+
+    free (key);
+}
+
+/*
+ * Gets a pointer to a shared string.
+ *
+ * A shared string is an entry in the hashtable "string_hashtable_shared", with:
+ * - key: reference count (unsigned integer on 32 bits) + string
+ * - value: NULL pointer (not used)
+ *
+ * The initial reference count is set to 1 and is incremented each time this
+ * function is called for a same string (string content, not the pointer).
+ *
+ * Returns the pointer to the shared string (start of string in key, after the
+ * reference count), NULL if error.
+ * The string returned has exactly same content as string received in argument,
+ * but the pointer to the string is different.
+ *
+ * IMPORTANT: the returned string must NEVER be changed in any way, because it
+ * is used itself as the key of the hashtable.
+ */
+
+const char *
+string_shared_get (const char *string)
+{
+    struct t_hashtable_item *ptr_item;
+    char *key;
+    int length;
+
+    if (!string_hashtable_shared)
+    {
+        /*
+         * use large htable inside hashtable to prevent too many collisions,
+         * which would slow down search of a string in the hashtable
+         */
+        string_hashtable_shared = hashtable_new (1024,
+                                                 WEECHAT_HASHTABLE_POINTER,
+                                                 WEECHAT_HASHTABLE_POINTER,
+                                                 &string_shared_hash_key,
+                                                 &string_shared_keycmp);
+        if (!string_hashtable_shared)
+            return NULL;
+
+        string_hashtable_shared->callback_free_key = &string_shared_free_key;
+    }
+
+    length = sizeof (string_shared_count_t) + strlen (string) + 1;
+    key = malloc (length);
+    if (!key)
+        return NULL;
+    *((string_shared_count_t *)key) = 1;
+    strcpy (key + sizeof (string_shared_count_t), string);
+
+    ptr_item = hashtable_get_item (string_hashtable_shared, key, NULL);
+    if (ptr_item)
+    {
+        /*
+         * the string already exists in the hashtable, then just increase the
+         * reference count on the string
+         */
+        (*((string_shared_count_t *)(ptr_item->key)))++;
+        free (key);
+    }
+    else
+    {
+        /* add the shared string in the hashtable */
+        ptr_item = hashtable_set (string_hashtable_shared, key, NULL);
+        if (!ptr_item)
+            free (key);
+    }
+
+    return (ptr_item) ?
+        ((const char *)ptr_item->key) + sizeof (string_shared_count_t) : NULL;
+}
+
+/*
+ * Frees a shared string.
+ *
+ * The reference count of the string is decremented. If it becomes 0, then the
+ * shared string is removed from the hashtable (and then the string is really
+ * destroyed).
+ */
+
+void
+string_shared_free (const char *string)
+{
+    string_shared_count_t *ptr_count;
+
+    ptr_count = (string_shared_count_t *)(string - sizeof (string_shared_count_t));
+
+    (*ptr_count)--;
+
+    if (*ptr_count == 0)
+        hashtable_remove (string_hashtable_shared, ptr_count);
+}
+
+/*
+ * Frees all allocated data.
+ */
+
+void
+string_end ()
+{
+    if (string_hashtable_shared)
+    {
+        hashtable_free (string_hashtable_shared);
+        string_hashtable_shared = NULL;
+    }
+}
diff --git a/src/core/wee-string.h b/src/core/wee-string.h
index f79795707..d79ae8fac 100644
--- a/src/core/wee-string.h
+++ b/src/core/wee-string.h
@@ -59,8 +59,12 @@ extern int string_has_highlight_regex_compiled (const char *string,
 extern int string_has_highlight_regex (const char *string, const char *regex);
 extern char **string_split (const char *string, const char *separators,
                             int keep_eol, int num_items_max, int *num_items);
+extern char **string_split_shared (const char *string, const char *separators,
+                                   int keep_eol, int num_items_max,
+                                   int *num_items);
 extern char **string_split_shell (const char *string);
 extern void string_free_split (char **split_string);
+extern void string_free_split_shared (char **split_string);
 extern char *string_build_with_split_string (const char **split_string,
                                              const char *separator);
 extern char **string_split_command (const char *command, char separator);
@@ -84,5 +88,8 @@ extern char *string_replace_with_callback (const char *string,
                                            char *(*callback)(void *data, const char *text),
                                            void *callback_data,
                                            int *errors);
+extern const char *string_shared_get (const char *string);
+extern void string_shared_free (const char *string);
+extern void string_end ();
 
 #endif /* __WEECHAT_STRING_H */
diff --git a/src/core/weechat.c b/src/core/weechat.c
index 218028075..e7a6d030a 100644
--- a/src/core/weechat.c
+++ b/src/core/weechat.c
@@ -488,6 +488,7 @@ main (int argc, char *argv[])
     unhook_all ();                      /* remove all hooks                 */
     hdata_end ();                       /* end hdata                        */
     eval_end ();                        /* end eval                         */
+    string_end ();                      /* end string                       */
     weechat_shutdown (EXIT_SUCCESS, 0); /* quit WeeChat (oh no, why?)       */
 
     return EXIT_SUCCESS;                /* make C compiler happy            */
diff --git a/src/gui/gui-line.c b/src/gui/gui-line.c
index 92bb6f5ef..724d632f8 100644
--- a/src/gui/gui-line.c
+++ b/src/gui/gui-line.c
@@ -86,6 +86,40 @@ gui_lines_free (struct t_gui_lines *lines)
     free (lines);
 }
 
+/*
+ * Allocates array with tags in a line_data.
+ */
+
+void
+gui_line_tags_alloc (struct t_gui_line_data *line_data, const char *tags)
+{
+    if (tags)
+    {
+        line_data->tags_array = string_split_shared (tags, ",", 0, 0,
+                                                     &line_data->tags_count);
+    }
+    else
+    {
+        line_data->tags_count = 0;
+        line_data->tags_array = NULL;
+    }
+}
+
+/*
+ * Frees array with tags in a line_data.
+ */
+
+void
+gui_line_tags_free (struct t_gui_line_data *line_data)
+{
+    if (line_data->tags_array)
+    {
+        string_free_split_shared (line_data->tags_array);
+        line_data->tags_count = 0;
+        line_data->tags_array = NULL;
+    }
+}
+
 /*
  * Checks if prefix on line is a nick and is the same as nick on previous line.
  *
@@ -871,10 +905,9 @@ gui_line_remove_from_list (struct t_gui_buffer *buffer,
     {
         if (line->data->str_time)
             free (line->data->str_time);
-        if (line->data->tags_array)
-            string_free_split (line->data->tags_array);
+        gui_line_tags_free (line->data);
         if (line->data->prefix)
-            free (line->data->prefix);
+            string_shared_free (line->data->prefix);
         if (line->data->message)
             free (line->data->message);
         free (line->data);
@@ -1090,19 +1123,10 @@ gui_line_add (struct t_gui_buffer *buffer, time_t date,
     new_line->data->date = date;
     new_line->data->date_printed = date_printed;
     new_line->data->str_time = gui_chat_get_time_string (date);
-    if (tags)
-    {
-        new_line->data->tags_array = string_split (tags, ",", 0, 0,
-                                                   &new_line->data->tags_count);
-    }
-    else
-    {
-        new_line->data->tags_count = 0;
-        new_line->data->tags_array = NULL;
-    }
+    gui_line_tags_alloc (new_line->data, tags);
     new_line->data->refresh_needed = 0;
     new_line->data->prefix = (prefix) ?
-        strdup (prefix) : ((date != 0) ? strdup ("") : NULL);
+        (char *)string_shared_get (prefix) : ((date != 0) ? (char *)string_shared_get ("") : NULL);
     new_line->data->prefix_length = (prefix) ?
         gui_chat_strlen_screen (prefix) : 0;
     new_line->data->message = (message) ? strdup (message) : strdup ("");
@@ -1318,8 +1342,8 @@ void
 gui_line_clear (struct t_gui_line *line)
 {
     if (line->data->prefix)
-        free (line->data->prefix);
-    line->data->prefix = strdup ("");
+        string_shared_free (line->data->prefix);
+    line->data->prefix = (char *)string_shared_get ("");
 
     if (line->data->message)
         free (line->data->message);
@@ -1521,18 +1545,8 @@ gui_line_hdata_line_data_update_cb (void *data,
     if (hashtable_has_key (hashtable, "tags_array"))
     {
         value = hashtable_get (hashtable, "tags_array");
-        if (line_data->tags_array)
-            string_free_split (line_data->tags_array);
-        if (value)
-        {
-            line_data->tags_array = string_split (value, ",", 0, 0,
-                                                  &line_data->tags_count);
-        }
-        else
-        {
-            line_data->tags_count = 0;
-            line_data->tags_array = NULL;
-        }
+        gui_line_tags_free (line_data);
+        gui_line_tags_alloc (line_data, value);
         rc++;
     }
 
diff --git a/src/gui/gui-nicklist.c b/src/gui/gui-nicklist.c
index e0e21eb77..7c82699e6 100644
--- a/src/gui/gui-nicklist.c
+++ b/src/gui/gui-nicklist.c
@@ -268,8 +268,8 @@ gui_nicklist_add_group (struct t_gui_buffer *buffer,
     if (!new_group)
         return NULL;
 
-    new_group->name = strdup (name);
-    new_group->color = (color) ? strdup (color) : NULL;
+    new_group->name = (char *)string_shared_get (name);
+    new_group->color = (color) ? (char *)string_shared_get (color) : NULL;
     new_group->visible = visible;
     new_group->parent = (parent_group) ? parent_group : buffer->nicklist_root;
     new_group->level = (new_group->parent) ? new_group->parent->level + 1 : 0;
@@ -442,10 +442,10 @@ gui_nicklist_add_nick (struct t_gui_buffer *buffer,
         return NULL;
 
     new_nick->group = (group) ? group : buffer->nicklist_root;
-    new_nick->name = strdup (name);
-    new_nick->color = (color) ? strdup (color) : NULL;
-    new_nick->prefix = (prefix) ? strdup (prefix) : NULL;
-    new_nick->prefix_color = (prefix_color) ? strdup (prefix_color) : NULL;
+    new_nick->name = (char *)string_shared_get (name);
+    new_nick->color = (color) ? (char *)string_shared_get (color) : NULL;
+    new_nick->prefix = (prefix) ? (char *)string_shared_get (prefix) : NULL;
+    new_nick->prefix_color = (prefix_color) ? (char *)string_shared_get (prefix_color) : NULL;
     new_nick->visible = visible;
 
     gui_nicklist_insert_nick_sorted (new_nick->group, new_nick);
@@ -495,13 +495,13 @@ gui_nicklist_remove_nick (struct t_gui_buffer *buffer,
 
     /* free data */
     if (nick->name)
-        free (nick->name);
+        string_shared_free (nick->name);
     if (nick->color)
-        free (nick->color);
+        string_shared_free (nick->color);
     if (nick->prefix)
-        free (nick->prefix);
+        string_shared_free (nick->prefix);
     if (nick->prefix_color)
-        free (nick->prefix_color);
+        string_shared_free (nick->prefix_color);
 
     buffer->nicklist_count--;
     buffer->nicklist_nicks_count--;
@@ -575,9 +575,9 @@ gui_nicklist_remove_group (struct t_gui_buffer *buffer,
 
     /* free data */
     if (group->name)
-        free (group->name);
+        string_shared_free (group->name);
     if (group->color)
-        free (group->color);
+        string_shared_free (group->color);
 
     if (group->visible)
     {
@@ -884,8 +884,8 @@ gui_nicklist_group_set (struct t_gui_buffer *buffer,
     if (string_strcasecmp (property, "color") == 0)
     {
         if (group->color)
-            free (group->color);
-        group->color = (value[0]) ? strdup (value) : NULL;
+            string_shared_free (group->color);
+        group->color = (value[0]) ? (char *)string_shared_get (value) : NULL;
         group_changed = 1;
     }
     else if (string_strcasecmp (property, "visible") == 0)
@@ -995,22 +995,22 @@ gui_nicklist_nick_set (struct t_gui_buffer *buffer,
     if (string_strcasecmp (property, "color") == 0)
     {
         if (nick->color)
-            free (nick->color);
-        nick->color = (value[0]) ? strdup (value) : NULL;
+            string_shared_free (nick->color);
+        nick->color = (value[0]) ? (char *)string_shared_get (value) : NULL;
         nick_changed = 1;
     }
     else if (string_strcasecmp (property, "prefix") == 0)
     {
         if (nick->prefix)
-            free (nick->prefix);
-        nick->prefix = (value[0]) ? strdup (value) : NULL;
+            string_shared_free (nick->prefix);
+        nick->prefix = (value[0]) ? (char *)string_shared_get (value) : NULL;
         nick_changed = 1;
     }
     else if (string_strcasecmp (property, "prefix_color") == 0)
     {
         if (nick->prefix_color)
-            free (nick->prefix_color);
-        nick->prefix_color = (value[0]) ? strdup (value) : NULL;
+            string_shared_free (nick->prefix_color);
+        nick->prefix_color = (value[0]) ? (char *)string_shared_get (value) : NULL;
         nick_changed = 1;
     }
     else if (string_strcasecmp (property, "visible") == 0)