diff --git a/README.md b/README.md
index 20c7f73..52a9f1d 100644
--- a/README.md
+++ b/README.md
@@ -66,6 +66,7 @@ type Person struct {
 
 This package currently provides the following checkers:
 
+- [alphanumeric](doc/checkers/alphanumeric.md) checks if the given string consists of only alphanumeric characters.
 - [ascii](doc/checkers/ascii.md) checks if the given string consists of only ASCII characters.
 - [digits](doc/checkers/digits.md) checks if the given string consists of only digit characters.
 - [max](doc/checkers/max.md) checks if the given value is less than the given maximum.
diff --git a/alphanumeric.go b/alphanumeric.go
new file mode 100644
index 0000000..bea70d4
--- /dev/null
+++ b/alphanumeric.go
@@ -0,0 +1,37 @@
+package checker
+
+import (
+	"reflect"
+	"unicode"
+)
+
+// CheckerAlphanumeric is the name of the checker.
+const CheckerAlphanumeric = "alphanumeric"
+
+// ResultNotAlphanumeric indicates that the given string contains non-alphanumeric characters.
+const ResultNotAlphanumeric = "NOT_ALPHANUMERIC"
+
+// IsAlphanumeric checks if the given string consists of only alphanumeric characters.
+func IsAlphanumeric(value string) Result {
+	for _, c := range value {
+		if !unicode.IsDigit(c) && !unicode.IsLetter(c) {
+			return ResultNotAlphanumeric
+		}
+	}
+
+	return ResultValid
+}
+
+// makeAlphanumeric makes a checker function for the alphanumeric checker.
+func makeAlphanumeric(_ string) CheckFunc {
+	return checkAlphanumeric
+}
+
+// checkAlphanumeric checks if the given string consists of only alphanumeric characters.
+func checkAlphanumeric(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	return IsAlphanumeric(value.String())
+}
diff --git a/alphanumeric_test.go b/alphanumeric_test.go
new file mode 100644
index 0000000..82ee9c4
--- /dev/null
+++ b/alphanumeric_test.go
@@ -0,0 +1,57 @@
+package checker
+
+import "testing"
+
+func TestIsAlphanumericInvalid(t *testing.T) {
+	if IsAlphanumeric("-/") == ResultValid {
+		t.Fail()
+	}
+}
+
+func TestIsAlphanumericValid(t *testing.T) {
+	if IsAlphanumeric("ABcd1234") != ResultValid {
+		t.Fail()
+	}
+}
+
+func TestCheckAlphanumericNonString(t *testing.T) {
+	defer FailIfNoPanic(t)
+
+	type User struct {
+		Username int `checkers:"alphanumeric"`
+	}
+
+	user := &User{}
+
+	Check(user)
+}
+
+func TestCheckAlphanumericInvalid(t *testing.T) {
+	type User struct {
+		Username string `checkers:"alphanumeric"`
+	}
+
+	user := &User{
+		Username: "user-/",
+	}
+
+	_, valid := Check(user)
+	if valid {
+		t.Fail()
+	}
+}
+
+func TestCheckAlphanumericValid(t *testing.T) {
+	type User struct {
+		Username string `checkers:"alphanumeric"`
+	}
+
+	user := &User{
+		Username: "ABcd1234",
+	}
+
+	_, valid := Check(user)
+	if !valid {
+		t.Fail()
+	}
+}
diff --git a/ascii.go b/ascii.go
index c6c0523..f41faa3 100644
--- a/ascii.go
+++ b/ascii.go
@@ -13,8 +13,8 @@ const ResultNotAscii = "NOT_ASCII"
 
 // IsAscii checks if the given string consists of only ASCII characters.
 func IsAscii(value string) Result {
-	for i := 0; i < len(value); i++ {
-		if value[i] > unicode.MaxASCII {
+	for _, c := range value {
+		if c > unicode.MaxASCII {
 			return ResultNotAscii
 		}
 	}
diff --git a/checker.go b/checker.go
index d298934..e2e23f3 100644
--- a/checker.go
+++ b/checker.go
@@ -31,14 +31,15 @@ const ResultValid Result = "VALID"
 
 // makers provides mapping to maker function for the checkers.
 var makers = map[string]MakeFunc{
-	CheckerAscii:     makeAscii,
-	CheckerDigits:    makeDigits,
-	CheckerMax:       makeMax,
-	CheckerMaxLength: makeMaxLength,
-	CheckerMin:       makeMin,
-	CheckerMinLength: makeMinLength,
-	CheckerRequired:  makeRequired,
-	CheckerSame:      makeSame,
+	CheckerAlphanumeric: makeAlphanumeric,
+	CheckerAscii:        makeAscii,
+	CheckerDigits:       makeDigits,
+	CheckerMax:          makeMax,
+	CheckerMaxLength:    makeMaxLength,
+	CheckerMin:          makeMin,
+	CheckerMinLength:    makeMinLength,
+	CheckerRequired:     makeRequired,
+	CheckerSame:         makeSame,
 }
 
 // Register registers the given checker name and the maker function.
diff --git a/digits.go b/digits.go
index 4ab56ac..ee16598 100644
--- a/digits.go
+++ b/digits.go
@@ -2,6 +2,7 @@ package checker
 
 import (
 	"reflect"
+	"unicode"
 )
 
 // CheckerDigits is the name of the checker.
@@ -12,8 +13,8 @@ const ResultNotDigits = "NOT_DIGITS"
 
 // IsDigits checks if the given string consists of only digit characters.
 func IsDigits(value string) Result {
-	for i := 0; i < len(value); i++ {
-		if value[i] < '0' || value[i] > '9' {
+	for _, c := range value {
+		if !unicode.IsDigit(c) {
 			return ResultNotDigits
 		}
 	}
diff --git a/doc/checkers/alphanumeric.md b/doc/checkers/alphanumeric.md
new file mode 100644
index 0000000..2cb89b6
--- /dev/null
+++ b/doc/checkers/alphanumeric.md
@@ -0,0 +1,28 @@
+# Alphanumeric Checker
+
+The ```alphanumeric``` checker checks if the given string consists of only alphanumeric characters. If the string contains non-alphanumeric characters, the checker will return the ```NOT_ALPHANUMERIC``` result. Here is an example:
+
+```golang
+type User struct {
+  Username string `checkers:"alphanumeric"`
+}
+
+user := &User{
+  Username: "ABcd1234",
+}
+
+_, valid := Check(user)
+if !valid {
+  // Send the mistakes back to the user
+}
+```
+
+In your custom checkers, you can call the ```alphanumeric``` checker function ```IsAlphanumeric``` to validate the user input. Here is an example:
+
+```golang
+result := IsAlphanumeric("ABcd1234")
+
+if result != ResultValid {
+  // Send the mistakes back to the user
+}
+```