diff --git a/go.mod b/go.mod
index b2158ce..0e1d138 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,10 @@ module gitlab.com/ekzyis/hnbot
 go 1.20
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/namsral/flag v1.7.4-pre // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.8.2 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 4c16f8b..893bfa6 100644
--- a/go.sum
+++ b/go.sum
@@ -1,4 +1,20 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
 github.com/namsral/flag v1.7.4-pre h1:b2ScHhoCUkbsq0d2C15Mv+VU8bl8hAXV8arnWiOHNZs=
 github.com/namsral/flag v1.7.4-pre/go.mod h1:OXldTctbM6SWH1K899kPZcf65KxJiD7MsceFUpB5yDo=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/sn.go b/sn.go
index 0722d2e..7d801a1 100644
--- a/sn.go
+++ b/sn.go
@@ -13,6 +13,18 @@ type GraphQLPayload struct {
 	Variables map[string]interface{} `json:"variables,omitempty"`
 }
 
+type Dupe struct {
+	Id    int    `json:"id,string"`
+	Url   string `json:"url"`
+	Title string `json:"title"`
+}
+
+type DupesResponse struct {
+	Data struct {
+		Dupes []Dupe `json:"dupes"`
+	} `json:"data"`
+}
+
 func filterByRelevanceForSN(stories *[]Story) *[]Story {
 	// TODO: filter by relevance
 
@@ -20,8 +32,55 @@ func filterByRelevanceForSN(stories *[]Story) *[]Story {
 	return &slice
 }
 
+func fetchDupes(url string) *[]Dupe {
+	body := GraphQLPayload{
+		Query: `
+			query Dupes($url: String!) {
+				dupes(url: $url) {
+					id
+					url
+					title
+				}
+			}`,
+		Variables: map[string]interface{}{
+			"url": url,
+		},
+	}
+
+	bodyJSON, err := json.Marshal(body)
+	if err != nil {
+		log.Fatal("Error during json.Marshal:", err)
+	}
+
+	apiUrl := "https://stacker.news/api/graphql"
+	req, err := http.NewRequest("POST", apiUrl, bytes.NewBuffer(bodyJSON))
+	if err != nil {
+		panic(err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Cookie", fmt.Sprintf("__Host-next-auth.csrf-token=%s", SnApiToken))
+
+	client := http.DefaultClient
+	resp, err := client.Do(req)
+	if err != nil {
+		panic(err)
+	}
+	defer resp.Body.Close()
+
+	var dupesResp DupesResponse
+	err = json.NewDecoder(resp.Body).Decode(&dupesResp)
+	if err != nil {
+		log.Fatal("Error decoding dupes JSON:", err)
+	}
+
+	return &dupesResp.Data.Dupes
+}
+
 func postToSN(story *Story) {
-	// TODO: check for dupes first
+	dupes := fetchDupes(story.Url)
+	if len(*dupes) > 0 {
+		return
+	}
 
 	body := GraphQLPayload{
 		Query: `
@@ -42,8 +101,8 @@ func postToSN(story *Story) {
 		log.Fatal("Error during json.Marshal:", err)
 	}
 
-	url := "https://stacker.news/api/graphql"
-	req, err := http.NewRequest("POST", url, bytes.NewBuffer(bodyJSON))
+	apiUrl := "https://stacker.news/api/graphql"
+	req, err := http.NewRequest("POST", apiUrl, bytes.NewBuffer(bodyJSON))
 	if err != nil {
 		panic(err)
 	}
@@ -57,5 +116,5 @@ func postToSN(story *Story) {
 	}
 	defer resp.Body.Close()
 
-	log.Printf("POST %s %d\n", url, resp.StatusCode)
+	log.Printf("POST %s %d\n", apiUrl, resp.StatusCode)
 }
diff --git a/sn_test.go b/sn_test.go
new file mode 100644
index 0000000..020e5cc
--- /dev/null
+++ b/sn_test.go
@@ -0,0 +1,14 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFetchDupes(t *testing.T) {
+	// TODO: mock HTTP request
+	url := "https://en.wikipedia.org/wiki/Dishwasher_salmon"
+	dupes := fetchDupes(url)
+	assert.NotEmpty(t, *dupes, "Expected at least one duplicate")
+}