diff --git a/src/lib/ares__buf.c b/src/lib/ares__buf.c
index 0296dbaf..7da5249a 100644
--- a/src/lib/ares__buf.c
+++ b/src/lib/ares__buf.c
@@ -793,6 +793,34 @@ static void ares__buf_destroy_cb(void *arg)
   ares__buf_destroy(arg);
 }
 
+static ares_bool_t ares__buf_split_isduplicate(ares__llist_t *list,
+                                               const unsigned char *val,
+                                               size_t len,
+                                               ares__buf_split_t flags)
+{
+  ares__llist_node_t *node;
+
+  for (node = ares__llist_node_first(list); node != NULL;
+       node = ares__llist_node_next(node)) {
+    ares__buf_t          *buf  = ares__llist_node_val(node);
+    size_t                plen = 0;
+    const unsigned char  *ptr  = ares__buf_peek(buf, &plen);
+
+    /* Can't be duplicate if lengths mismatch */
+    if (plen != len)
+      continue;
+
+    if (flags & ARES_BUF_SPLIT_CASE_INSENSITIVE) {
+      if (ares__memeq_ci(ptr, val, len))
+        return ARES_TRUE;
+    } else {
+      if (memcmp(ptr, val, len) == 0)
+        return ARES_TRUE;
+    }
+  }
+  return ARES_FALSE;
+}
+
 ares_status_t ares__buf_split(ares__buf_t *buf, const unsigned char *delims,
                               size_t delims_len, ares__buf_split_t flags,
                               ares__llist_t **list)
@@ -826,23 +854,27 @@ ares_status_t ares__buf_split(ares__buf_t *buf, const unsigned char *delims,
       const unsigned char *ptr = ares__buf_tag_fetch(buf, &len);
       ares__buf_t         *data;
 
-      /* Since we don't allow const buffers of 0 length, and user wants 0-length
-       * buffers, swap what we do here */
-      if (len) {
-        data = ares__buf_create_const(ptr, len);
-      } else {
-        data = ares__buf_create();
-      }
+      if (!(flags & ARES_BUF_SPLIT_NO_DUPLICATES) ||
+          !ares__buf_split_isduplicate(*list, ptr, len, flags)) {
 
-      if (data == NULL) {
-        status = ARES_ENOMEM;
-        goto done;
-      }
+        /* Since we don't allow const buffers of 0 length, and user wants
+         * 0-length buffers, swap what we do here */
+        if (len) {
+          data = ares__buf_create_const(ptr, len);
+        } else {
+          data = ares__buf_create();
+        }
 
-      if (ares__llist_insert_last(*list, data) == NULL) {
-        ares__buf_destroy(data);
-        status = ARES_ENOMEM;
-        goto done;
+        if (data == NULL) {
+          status = ARES_ENOMEM;
+          goto done;
+        }
+
+        if (ares__llist_insert_last(*list, data) == NULL) {
+          ares__buf_destroy(data);
+          status = ARES_ENOMEM;
+          goto done;
+        }
       }
     }
 
diff --git a/src/lib/ares__buf.h b/src/lib/ares__buf.h
index 4e6a8971..77e3d255 100644
--- a/src/lib/ares__buf.h
+++ b/src/lib/ares__buf.h
@@ -420,7 +420,11 @@ typedef enum {
   /*! Allow blank sections, by default blank sections are not emitted.  If using
    *  ARES_BUF_SPLIT_DONT_CONSUME_DELIMS, the delimiter is not counted as part
    *  of the section */
-  ARES_BUF_SPLIT_ALLOW_BLANK = 1 << 1
+  ARES_BUF_SPLIT_ALLOW_BLANK = 1 << 1,
+  /*! Remove duplicate entries */
+  ARES_BUF_SPLIT_NO_DUPLICATES = 1 << 2,
+  /*! Perform case-insenstive matching when comparing values */
+  ARES_BUF_SPLIT_CASE_INSENSITIVE = 1 << 3
 } ares__buf_split_t;
 
 /*! Split the provided buffer into multiple sub-buffers stored in the variable
diff --git a/src/lib/ares__htable.c b/src/lib/ares__htable.c
index 39708fe3..a10929ea 100644
--- a/src/lib/ares__htable.c
+++ b/src/lib/ares__htable.c
@@ -399,30 +399,6 @@ unsigned int ares__htable_hash_FNV1a(const unsigned char *key, size_t key_len,
   return hv;
 }
 
-/* tolower() is locale-specific.  Use a lookup table fast conversion that only
- * operates on ASCII */
-static const unsigned char ares__tolower_lookup[] = {
-  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C,
-  0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
-  0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26,
-  0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33,
-  0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40,
-  0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D,
-  0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A,
-  0x5B, 0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
-  0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74,
-  0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F, 0x80, 0x81,
-  0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E,
-  0x8F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B,
-  0x9C, 0x9D, 0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8,
-  0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5,
-  0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF, 0xC0, 0xC1, 0xC2,
-  0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF,
-  0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC,
-  0xDD, 0xDE, 0xDF, 0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9,
-  0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6,
-  0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF
-};
 
 /* Case insensitive version, meant for ASCII strings */
 unsigned int ares__htable_hash_FNV1a_casecmp(const unsigned char *key,
@@ -433,7 +409,7 @@ unsigned int ares__htable_hash_FNV1a_casecmp(const unsigned char *key,
   size_t       i;
 
   for (i = 0; i < key_len; i++) {
-    hv ^= (unsigned int)ares__tolower_lookup[key[i]];
+    hv ^= (unsigned int)ares__tolower(key[i]);
     /* hv *= 0x01000193 */
     hv += (hv << 1) + (hv << 4) + (hv << 7) + (hv << 8) + (hv << 24);
   }
diff --git a/src/lib/ares_str.c b/src/lib/ares_str.c
index b44f4819..bed3cddf 100644
--- a/src/lib/ares_str.c
+++ b/src/lib/ares_str.c
@@ -109,3 +109,45 @@ ares_bool_t ares_str_isnum(const char *str)
   }
   return ARES_TRUE;
 }
+
+/* tolower() is locale-specific.  Use a lookup table fast conversion that only
+ * operates on ASCII */
+static const unsigned char ares__tolower_lookup[] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C,
+  0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
+  0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26,
+  0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33,
+  0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40,
+  0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D,
+  0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7A,
+  0x5B, 0x5C, 0x5D, 0x5E, 0x5F, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
+  0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74,
+  0x75, 0x76, 0x77, 0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F, 0x80, 0x81,
+  0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E,
+  0x8F, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9A, 0x9B,
+  0x9C, 0x9D, 0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8,
+  0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5,
+  0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF, 0xC0, 0xC1, 0xC2,
+  0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF,
+  0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC,
+  0xDD, 0xDE, 0xDF, 0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9,
+  0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6,
+  0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF
+};
+
+unsigned char ares__tolower(unsigned char c)
+{
+  return ares__tolower_lookup[c];
+}
+
+ares_bool_t ares__memeq_ci(const unsigned char *ptr, const unsigned char *val,
+                           size_t len)
+{
+  size_t i;
+  for (i=0; i<len; i++) {
+    if (ares__tolower_lookup[ptr[i]] != ares__tolower_lookup[val[i]]) {
+      return ARES_FALSE;
+    }
+  }
+  return ARES_TRUE;
+}
diff --git a/src/lib/ares_str.h b/src/lib/ares_str.h
index c1cfa9f7..4e3428f7 100644
--- a/src/lib/ares_str.h
+++ b/src/lib/ares_str.h
@@ -48,4 +48,8 @@ size_t      ares_strcpy(char *dest, const char *src, size_t dest_size);
 
 ares_bool_t ares_str_isnum(const char *str);
 
+unsigned char ares__tolower(unsigned char c);
+ares_bool_t ares__memeq_ci(const unsigned char *ptr, const unsigned char *val,
+                           size_t len);
+
 #endif /* HEADER_CARES_STRDUP_H */
diff --git a/src/lib/ares_strsplit.c b/src/lib/ares_strsplit.c
index dbb79429..79043543 100644
--- a/src/lib/ares_strsplit.c
+++ b/src/lib/ares_strsplit.c
@@ -71,15 +71,16 @@ char **ares__strsplit_duplicate(char **elms, size_t num_elm)
   return out;
 }
 
+
 char **ares__strsplit(const char *in, const char *delms, size_t *num_elm)
 {
-  const char *p;
-  char      **table;
-  void       *tmp;
-  size_t      i;
-  size_t      j;
-  size_t      k;
-  size_t      count;
+  ares_status_t       status;
+  ares__buf_t        *buf   = NULL;
+  ares__llist_t      *llist = NULL;
+  ares__llist_node_t *node;
+  char              **out   = NULL;
+  size_t              cnt   = 0;
+  size_t              idx   = 0;
 
   if (in == NULL || delms == NULL || num_elm == NULL) {
     return NULL;
@@ -87,56 +88,56 @@ char **ares__strsplit(const char *in, const char *delms, size_t *num_elm)
 
   *num_elm = 0;
 
-  /* count non-empty delimited substrings */
-  count = 0;
-  p     = in;
-  do {
-    i = strcspn(p, delms);
-    if (i != 0) {
-      /* string is non-empty */
-      count++;
-      p += i;
-    }
-  } while (*p++ != 0);
-
-  if (count == 0) {
+  buf = ares__buf_create_const((const unsigned char *)in, ares_strlen(in));
+  if (buf == NULL) {
     return NULL;
   }
-  table = ares_malloc(count * sizeof(*table));
-  if (table == NULL) {
-    return NULL;
+
+  status = ares__buf_split(buf, (const unsigned char *)delms,
+                           ares_strlen(delms),
+                           ARES_BUF_SPLIT_NO_DUPLICATES|
+                           ARES_BUF_SPLIT_CASE_INSENSITIVE,
+                           &llist);
+  if (status != ARES_SUCCESS) {
+    goto done;
+  }
+
+  cnt = ares__llist_len(llist);
+  if (cnt == 0) {
+    status = ARES_EFORMERR;
+    goto done;
   }
 
-  j = 0; /* current table entry */
-  /* re-calculate indices and allocate new strings for table */
-  for (p = in; j < count; p += i + 1) {
-    i = strcspn(p, delms);
-    if (i != 0) {
-      for (k = 0; k < j; k++) {
-        if (strncasecmp(table[k], p, i) == 0 && table[k][i] == 0) {
-          break;
-        }
-      }
-      if (k == j) {
-        /* copy unique strings only */
-        table[j] = ares_malloc(i + 1);
-        if (table[j] == NULL) {
-          ares__strsplit_free(table, j);
-          return NULL;
-        }
-        ares_strcpy(table[j], p, i + 1);
-        j++;
-      } else {
-        count--;
-      }
+
+  out = ares_malloc_zero(cnt * sizeof(*out));
+  if (out == NULL) {
+    status = ARES_ENOMEM;
+    goto done;
+  }
+
+  for (node = ares__llist_node_first(llist); node != NULL;
+       node = ares__llist_node_next(node)) {
+    ares__buf_t *val  = ares__llist_node_val(node);
+    char        *temp = NULL;
+
+    status = ares__buf_fetch_str_dup(val, ares__buf_len(val), &temp);
+    if (status != ARES_SUCCESS) {
+      goto done;
     }
+
+    out[idx++] = temp;
   }
 
-  tmp = ares_realloc(table, count * sizeof(*table));
-  if (tmp != NULL) {
-    table = tmp;
+  *num_elm = cnt;
+  status   = ARES_SUCCESS;
+
+done:
+  ares__llist_destroy(llist);
+  ares__buf_destroy(buf);
+  if (status != ARES_SUCCESS) {
+    ares__strsplit_free(out, cnt);
+    out = NULL;
   }
 
-  *num_elm = count;
-  return table;
+  return out;
 }
diff --git a/src/lib/ares_strsplit.h b/src/lib/ares_strsplit.h
index c3e61e17..af650eee 100644
--- a/src/lib/ares_strsplit.h
+++ b/src/lib/ares_strsplit.h
@@ -35,7 +35,7 @@
  *             Each character in the string is a delimiter so
  *             there can be multiple delimiters to split on.
  *             E.g. ", " will split on all comma's and spaces.
- *             Duplicate entries are removed.
+ *             Duplicate (case-insensitive) entries are removed.
  * param num_elm Return parameter of the number of elements
  *               in the result array.
  *