diff --git a/d8/d8.go b/d8/d8.go
new file mode 100644
index 0000000..b8ec4ab
--- /dev/null
+++ b/d8/d8.go
@@ -0,0 +1,264 @@
+package d8
+
+import (
+	"log"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+func D8(in string) int {
+	lines := strings.Split(strings.TrimSpace(in), "\n")
+
+	sum := 0
+
+	for _, line := range lines {
+		for _, digit := range strings.Split(strings.Split(line, "|")[1], " ") {
+			if len(digit) == 2 || len(digit) == 3 || len(digit) == 4 || len(digit) == 7 {
+				sum++
+			}
+		}
+	}
+
+	return sum
+}
+
+func difference(a []string, b []string) []string {
+	needle := a
+	haystack := b
+
+	if len(a) > len(b) {
+		needle = b
+		haystack = a
+	}
+
+	mb := make(map[string]struct{}, len(needle))
+	for _, x := range needle {
+		mb[x] = struct{}{}
+	}
+	var diff []string
+	for _, x := range haystack {
+		if _, found := mb[x]; !found {
+			diff = append(diff, x)
+		}
+	}
+	return diff
+}
+
+func merge(a []string, b []string) []string {
+	return append(append([]string{}, a...), b...)
+}
+
+func findSegment(digits [][]string, part []string) string {
+	for _, digit := range digits {
+		diff := difference(digit, part)
+
+		if len(digit) > len(part) && len(diff) == 1 {
+			return diff[0]
+		}
+	}
+
+	log.Fatal("can't find segment")
+
+	return ""
+}
+
+//  aaaa
+// b    c
+// b    c
+//  dddd
+// e    f
+// e    f
+//  gggg
+//
+// a: 0, c: 1, f: 2, g: 3, e: 4, b: 5, d: 6
+func findDisplay(digitsAsString string) []string {
+	display := make([]string, 7)
+
+	digits := [][]string{}
+	splitted := strings.Split(digitsAsString, " ")
+	sort.Slice(splitted, func(i, j int) bool { return len(splitted[i]) < len(splitted[j]) })
+	for _, digit := range splitted {
+		digits = append(digits, strings.Split(digit, ""))
+	}
+
+	// a
+	display[0] = findSegment(digits, digits[0])
+	// g
+	display[3] = findSegment(digits, merge(digits[2], []string{display[0]}))
+	// e
+	display[4] = findSegment(digits, merge(digits[2], []string{display[0], display[3]}))
+	// d
+	display[6] = findSegment(digits, merge(digits[1], []string{display[3]}))
+	// b
+	display[5] = findSegment(digits, merge(digits[1], []string{display[3], display[4], display[6]}))
+	// f
+	display[2] = findSegment(digits, []string{display[0], display[3], display[4], display[5], display[6]})
+	// c
+	display[1] = findSegment(digits, []string{display[0], display[2], display[3], display[4], display[5], display[6]})
+
+	return display
+}
+
+func isOne(digit []string, display []string) bool {
+	return len(digit) == 2
+}
+
+func isTwo(digit []string, display []string) bool {
+
+	if len(digit) != 5 {
+		return false
+	}
+
+	two := strings.Join([]string{display[0], display[1], display[3], display[4], display[6]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(two, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func isThree(digit []string, display []string) bool {
+
+	if len(digit) != 5 {
+		return false
+	}
+
+	three := strings.Join([]string{display[0], display[1], display[2], display[3], display[6]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(three, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func isFour(digit []string, display []string) bool {
+	return len(digit) == 4
+}
+
+func isFive(digit []string, display []string) bool {
+
+	if len(digit) != 5 {
+		return false
+	}
+
+	three := strings.Join([]string{display[0], display[2], display[3], display[5], display[6]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(three, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func isSix(digit []string, display []string) bool {
+
+	if len(digit) != 6 {
+		return false
+	}
+
+	three := strings.Join([]string{display[0], display[2], display[3], display[4], display[5], display[6]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(three, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func isSeven(digit []string, display []string) bool {
+	return len(digit) == 3
+}
+
+func isEight(digit []string, display []string) bool {
+	return len(digit) == 7
+}
+
+func isNine(digit []string, display []string) bool {
+
+	if len(digit) != 6 {
+		return false
+	}
+
+	three := strings.Join([]string{display[0], display[1], display[2], display[3], display[5], display[6]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(three, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func isZero(digit []string, display []string) bool {
+
+	if len(digit) != 6 {
+		return false
+	}
+
+	three := strings.Join([]string{display[0], display[1], display[2], display[3], display[4], display[5]}, "")
+
+	for _, segment := range digit {
+		if !strings.Contains(three, segment) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func digitToNumber(digit []string, display []string) int {
+	numberMap := map[int]func([]string, []string) bool{
+		0: isZero,
+		1: isOne,
+		2: isTwo,
+		3: isThree,
+		4: isFour,
+		5: isFive,
+		6: isSix,
+		7: isSeven,
+		8: isEight,
+		9: isNine,
+	}
+
+	for number, f := range numberMap {
+		if f(digit, display) {
+			return number
+		}
+	}
+	log.Fatal("wrong digit", digit, display)
+	return 0
+}
+
+func findCode(digitsAsString string, display []string) int {
+	numbers := []string{}
+	for _, digit := range strings.Split(digitsAsString, " ") {
+		numbers = append(numbers, strconv.Itoa(digitToNumber(strings.Split(digit, ""), display)))
+	}
+	asInt, _ := strconv.Atoi(strings.Join(numbers, ""))
+
+	return asInt
+}
+
+func D8P2(in string) int {
+	lines := strings.Split(strings.TrimSpace(in), "\n")
+	sum := 0
+	for _, line := range lines {
+		wiringsAndCode := strings.Split(line, " | ")
+		display := findDisplay(wiringsAndCode[0])
+		sum += findCode(wiringsAndCode[1], display)
+	}
+
+	return sum
+}
diff --git a/d8/d8_test.go b/d8/d8_test.go
new file mode 100644
index 0000000..9fb850a
--- /dev/null
+++ b/d8/d8_test.go
@@ -0,0 +1,37 @@
+package d8
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestD8(t *testing.T) {
+	input := `be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce`
+
+	assert.EqualValues(t, 26, D8(input))
+}
+
+func TestD8P2(t *testing.T) {
+	input := `be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce`
+
+	assert.EqualValues(t, 61229, D8P2(input))
+}
diff --git a/main.go b/main.go
index 376febb..34c79b1 100644
--- a/main.go
+++ b/main.go
@@ -14,6 +14,7 @@ import (
 	"github.com/fotonmoton/aoc2021/d5"
 	"github.com/fotonmoton/aoc2021/d6"
 	"github.com/fotonmoton/aoc2021/d7"
+	"github.com/fotonmoton/aoc2021/d8"
 )
 
 func main() {
@@ -40,4 +41,6 @@ func main() {
 	fmt.Printf("day 6 part 2: %v\n", d6.D6P2(client.Day(6), 256))
 	fmt.Printf("day 7: %v\n", d7.D7(client.Day(7)))
 	fmt.Printf("day 7 part 2: %v\n", d7.D7P2(client.Day(7)))
+	fmt.Printf("day 8: %v\n", d8.D8(client.Day(8)))
+	fmt.Printf("day 8 part 2: %v\n", d8.D8P2(client.Day(8)))
 }