diff --git a/src/lib/ares_init.c b/src/lib/ares_init.c
index 7f92ef67..738fc2aa 100644
--- a/src/lib/ares_init.c
+++ b/src/lib/ares_init.c
@@ -2000,7 +2000,7 @@ static int set_search(ares_channel channel, const char *str)
     channel->ndomains = -1;
   } /* LCOV_EXCL_STOP */
 
-  channel->domains  = ares_strsplit(str, ", ", 1, &cnt);
+  channel->domains  = ares_strsplit(str, ", ", &cnt);
   channel->ndomains = (int)cnt;
   if (channel->domains == NULL || channel->ndomains == 0) {
     channel->domains  = NULL;
diff --git a/src/lib/ares_strsplit.c b/src/lib/ares_strsplit.c
index 97b4e5d5..db1f66a4 100644
--- a/src/lib/ares_strsplit.c
+++ b/src/lib/ares_strsplit.c
@@ -22,46 +22,6 @@
 #include "ares.h"
 #include "ares_private.h"
 
-static int list_contains(char * const *list, size_t num_elem, const char *str, int insensitive)
-{
-  size_t len;
-  size_t i;
-
-  len = strlen(str);
-  for (i=0; i<num_elem; i++)
-  {
-    if (insensitive)
-    {
-#ifdef WIN32
-      if (strnicmp(list[i], str, len) == 0)
-#else
-      if (strncasecmp(list[i], str, len) == 0)
-#endif
-        return 1;
-    }
-    else
-    {
-      if (strncmp(list[i], str, len) == 0)
-        return 1;
-    }
-  }
-
-  return 0;
-}
-
-static int is_delim(char c, const char *delims, size_t num_delims)
-{
-  size_t i;
-
-  for (i=0; i<num_delims; i++)
-  {
-    if (c == delims[i])
-      return 1;
-  }
-  return 0;
-}
-
-
 void ares_strsplit_free(char **elms, size_t num_elm)
 {
   size_t i;
@@ -74,105 +34,67 @@ void ares_strsplit_free(char **elms, size_t num_elm)
   ares_free(elms);
 }
 
-
-char **ares_strsplit(const char *in, const char *delms, int make_set, size_t *num_elm)
-{
-  char *parsestr;
-  char **temp;
-  char **out;
-  size_t cnt;
-  size_t nelms;
-  size_t in_len;
-  size_t num_delims;
-  size_t i;
+char **ares_strsplit(const char *in, const char *delms, size_t *num_elm) {
+  const char *p;
+  char **table;
+  void *tmp;
+  size_t i, j, k, count;
 
   if (in == NULL || delms == NULL || num_elm == NULL)
     return NULL;
 
   *num_elm = 0;
 
-  in_len = strlen(in);
-  num_delims = strlen(delms);
-
-  /* Figure out how many elements. */
-  nelms = 1;
-  for (i=0; i<in_len; i++)
-  {
-    if (is_delim(in[i], delms, num_delims))
-    {
-      nelms++;
+  /* 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);
 
-  /* Copy of input so we can cut it up. */
-  parsestr = ares_strdup(in);
-  if (parsestr == NULL)
+  if (count == 0)
     return NULL;
-
-  /* Temporary array to store locations of start of each element
-   * within parsestr. */
-  temp = ares_malloc(nelms * sizeof(*temp));
-  if (temp == NULL)
-  {
-    ares_free(parsestr);
+  table = ares_malloc(count * sizeof(*table));
+  if (table == NULL)
     return NULL;
-  }
-  temp[0] = parsestr;
-  cnt = 1;
-  for (i=0; i<in_len && cnt<nelms; i++)
-  {
-    if (!is_delim(parsestr[i], delms, num_delims))
-      continue;
-
-    /* Replace sep with NULL. */
-    parsestr[i] = '\0';
-    /* Add the pointer to the array of elements */
-    temp[cnt] = parsestr+i+1;
-    cnt++;
-  }
 
-  /* Copy each element to our output array. */
-  out = ares_malloc(nelms * sizeof(*out));
-  if (out == NULL)
-  {
-    ares_free(parsestr);
-    ares_free(temp);
-    return NULL;
-  }
-
-  nelms = 0;
-  for (i=0; i<cnt; i++)
-  {
-    if (temp[i][0] == '\0')
-      continue;
-
-    if (make_set && list_contains(out, nelms, temp[i], 1))
-      continue;
-
-    out[nelms] = ares_strdup(temp[i]);
-    if (out[nelms] == NULL)
-    {
-      ares_strsplit_free(out, nelms);
-      ares_free(parsestr);
-      ares_free(temp);
-      return NULL;
+  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++) {
+#ifdef WIN32
+        if (strnicmp(table[k], p, i) == 0 && table[k][i] == 0)
+          break;
+#else
+        if (strncasecmp(table[k], p, i) == 0 && table[k][i] == 0)
+          break;
+#endif
+      }
+      if (k == j) {
+        /* copy unique strings only */
+        table[j] = ares_malloc(i + 1);
+        if (table[j] == NULL) {
+          ares_strsplit_free(table, j);
+          return NULL;
+        }
+        strncpy(table[j], p, i);
+        table[j++][i] = 0;
+      } else
+        count--;
     }
-    nelms++;
-  }
-
-
-  /* If there are no elements don't return an empty allocated
-   * array. */
-  if (nelms == 0)
-  {
-    ares_strsplit_free(out, nelms);
-    out = NULL;
   }
 
-  /* Get the true number of elements (recalculated because of make_set) */
-  *num_elm = nelms;
+  tmp = ares_realloc(table, count * sizeof (*table));
+  if (tmp != NULL)
+    table = tmp;
 
-  ares_free(parsestr);
-  ares_free(temp);
-  return out;
+  *num_elm = count;
+  return table;
 }
diff --git a/src/lib/ares_strsplit.h b/src/lib/ares_strsplit.h
index e00fd14d..96a2b1f1 100644
--- a/src/lib/ares_strsplit.h
+++ b/src/lib/ares_strsplit.h
@@ -18,22 +18,21 @@
 
 #include "ares_setup.h"
 
-/* Split a string on delem skipping empty elements.
+/* Split a string on delms skipping empty or duplicate elements.
  *
  * param in String to split.
- * param delims String of characters to treat as a delimitor.
- *              Each character in the string is a delimitor so
- *              there can be multiple delimitors to split on.
- *              E.g. ", " will split on all comma's and spaces.
- * param make_set Have the list be a Set where there are no
- *                duplicate entries. 1 for true, 0 or false.
+ * param delms String of characters to treat as a delimitor.
+ *             Each character in the string is a delimitor so
+ *             there can be multiple delimitors to split on.
+ *             E.g. ", " will split on all comma's and spaces.
+ *             Duplicate entries are removed.
  * param num_elm Return parameter of the number of elements
  *               in the result array.
  *
  * returns an allocated array of allocated string elements.
  *
  */
-char **ares_strsplit(const char *in, const char *delms, int make_set, size_t *num_elm);
+char **ares_strsplit(const char *in, const char *delms, size_t *num_elm);
 
 /* Frees the result returned from ares_strsplit(). */
 void ares_strsplit_free(char **elms, size_t num_elm);
diff --git a/test/ares-test-internal.cc b/test/ares-test-internal.cc
index 96d4edec..465ff1bb 100644
--- a/test/ares-test-internal.cc
+++ b/test/ares-test-internal.cc
@@ -19,6 +19,7 @@ extern "C" {
 #include "ares_nowarn.h"
 #include "ares_inet_net_pton.h"
 #include "ares_data.h"
+#include "ares_strsplit.h"
 #include "ares_private.h"
 #include "bitncmp.h"
 
@@ -47,6 +48,47 @@ void CheckPtoN4(int size, unsigned int value, const char *input) {
 }
 #endif
 
+#ifndef CARES_SYMBOL_HIDING
+TEST_F(LibraryTest, Strsplit) {
+  using std::vector;
+  using std::string;
+  size_t n;
+  struct {
+    vector<string> inputs;
+    vector<string> delimiters;
+    vector<vector<string>> expected;
+  } data = {
+    {
+      "",
+      " ",
+      "             ",
+      "example.com, example.co",
+      "        a, b, A,c,     d, e,,,D,e,e,E",
+    },
+    { ", ", ", ", ", ", ", ", ", " },
+    {
+      {}, {}, {},
+      { "example.com", "example.co" },
+      { "a", "b", "c", "d", "e" },
+    },
+  };
+  for(size_t i = 0; i < data.inputs.size(); i++) {
+    char **out = ares_strsplit(data.inputs.at(i).c_str(),
+                               data.delimiters.at(i).c_str(), &n);
+    if(data.expected.at(i).size() == 0) {
+      EXPECT_EQ(out, nullptr);
+    }
+    else {
+      EXPECT_EQ(n, data.expected.at(i).size());
+      for(size_t j = 0; j < n && j < data.expected.at(i).size(); j++) {
+        EXPECT_STREQ(out[j], data.expected.at(i).at(j).c_str());
+      }
+    }
+    ares_strsplit_free(out, n);
+  }
+}
+#endif
+
 TEST_F(LibraryTest, InetPtoN) {
   struct in_addr a4;
   struct in6_addr a6;