diff --git a/cmd/owl-web/handler.go b/cmd/owl-web/handler.go
index cd6e47c..f083376 100644
--- a/cmd/owl-web/handler.go
+++ b/cmd/owl-web/handler.go
@@ -85,6 +85,24 @@ func userWebmentionHandler(repo *owl.Repository) func(http.ResponseWriter, *http
 			return
 		}
 
+		if len(target[0]) < 7 || (target[0][:7] != "http://" && target[0][:8] != "https://") {
+			w.WriteHeader(http.StatusBadRequest)
+			w.Write([]byte("Not a valid target"))
+			return
+		}
+
+		if len(source[0]) < 7 || (source[0][:7] != "http://" && source[0][:8] != "https://") {
+			w.WriteHeader(http.StatusBadRequest)
+			w.Write([]byte("Not a valid source"))
+			return
+		}
+
+		if source[0] == target[0] {
+			w.WriteHeader(http.StatusBadRequest)
+			w.Write([]byte("target and source are equal"))
+			return
+		}
+
 		parts := strings.Split(target[0], "/")
 		if len(parts) < 2 {
 			w.WriteHeader(http.StatusNotFound)
diff --git a/cmd/owl-web/webmention_test.go b/cmd/owl-web/webmention_test.go
index 1b2db5e..3cdc62e 100644
--- a/cmd/owl-web/webmention_test.go
+++ b/cmd/owl-web/webmention_test.go
@@ -1,6 +1,7 @@
 package main_test
 
 import (
+	"h4kor/owl-blogs"
 	main "h4kor/owl-blogs/cmd/owl-web"
 	"net/http"
 	"net/http/httptest"
@@ -10,6 +11,36 @@ import (
 	"testing"
 )
 
+func setupWebmentionTest(repo owl.Repository, user owl.User, target string, source string) (*httptest.ResponseRecorder, error) {
+
+	data := url.Values{}
+	data.Set("target", target)
+	data.Set("source", source)
+
+	// Create Request and Response
+	req, err := http.NewRequest("POST", user.UrlPath()+"webmention/", strings.NewReader(data.Encode()))
+	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Add("Content-Length", strconv.Itoa(len(data.Encode())))
+
+	if err != nil {
+		return nil, err
+	}
+
+	rr := httptest.NewRecorder()
+	router := main.Router(&repo)
+	router.ServeHTTP(rr, req)
+
+	return rr, nil
+}
+
+func assertStatus(t *testing.T, rr *httptest.ResponseRecorder, expStatus int) {
+	if status := rr.Code; status != expStatus {
+		t.Errorf("handler returned wrong status code: got %v want %v",
+			status, expStatus)
+		return
+	}
+}
+
 func TestWebmentionHandleAccepts(t *testing.T) {
 	repo := getTestRepo()
 	user, _ := repo.CreateUser("test-1")
@@ -17,62 +48,118 @@ func TestWebmentionHandleAccepts(t *testing.T) {
 
 	target := post.FullUrl()
 	source := "https://example.com"
-	data := url.Values{}
-	data.Set("target", target)
-	data.Set("source", source)
-
-	// Create Request and Response
-	req, err := http.NewRequest("POST", user.UrlPath()+"webmention/", strings.NewReader(data.Encode()))
-	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
-	req.Header.Add("Content-Length", strconv.Itoa(len(data.Encode())))
 
+	rr, err := setupWebmentionTest(repo, user, target, source)
 	if err != nil {
 		t.Fatal(err)
 	}
-	rr := httptest.NewRecorder()
-	router := main.Router(&repo)
-	router.ServeHTTP(rr, req)
 
-	// Check the status code is what we expect.
-	if status := rr.Code; status != http.StatusAccepted {
-		t.Errorf("handler returned wrong status code: got %v want %v",
-			status, http.StatusAccepted)
-		t.Errorf("Body: %v", rr.Body)
-	}
+	assertStatus(t, rr, http.StatusAccepted)
 
 }
 
 func TestWebmentionWrittenToPost(t *testing.T) {
+
 	repo := getTestRepo()
 	user, _ := repo.CreateUser("test-1")
 	post, _ := user.CreateNewPost("post-1")
 
 	target := post.FullUrl()
 	source := "https://example.com"
-	data := url.Values{}
-	data.Set("target", target)
-	data.Set("source", source)
 
-	// Create Request and Response
-	req, err := http.NewRequest("POST", user.UrlPath()+"webmention/", strings.NewReader(data.Encode()))
-	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
-	req.Header.Add("Content-Length", strconv.Itoa(len(data.Encode())))
+	rr, err := setupWebmentionTest(repo, user, target, source)
 	if err != nil {
 		t.Fatal(err)
 	}
-	rr := httptest.NewRecorder()
-	router := main.Router(&repo)
-	router.ServeHTTP(rr, req)
 
 	// Check the status code is what we expect.
-	if status := rr.Code; status != http.StatusAccepted {
-		t.Errorf("handler returned wrong status code: got %v want %v",
-			status, http.StatusAccepted)
-		return
-	}
+	assertStatus(t, rr, http.StatusAccepted)
 
 	if len(post.Webmentions()) != 1 {
 		t.Errorf("no webmention written to post")
 	}
-
 }
+
+//
+// https://www.w3.org/TR/webmention/#h-request-verification
+//
+
+// The receiver MUST check that source and target are valid URLs [URL]
+// and are of schemes that are supported by the receiver.
+// (Most commonly this means checking that the source and target schemes are http or https).
+func TestWebmentionSourceValidation(t *testing.T) {
+
+	repo := getTestRepo()
+	user, _ := repo.CreateUser("test-1")
+	post, _ := user.CreateNewPost("post-1")
+
+	target := post.FullUrl()
+	source := "ftp://example.com"
+
+	rr, err := setupWebmentionTest(repo, user, target, source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertStatus(t, rr, http.StatusBadRequest)
+}
+
+func TestWebmentionTargetValidation(t *testing.T) {
+
+	repo := getTestRepo()
+	user, _ := repo.CreateUser("test-1")
+	post, _ := user.CreateNewPost("post-1")
+
+	target := "ftp://example.com"
+	source := post.FullUrl()
+
+	rr, err := setupWebmentionTest(repo, user, target, source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertStatus(t, rr, http.StatusBadRequest)
+}
+
+// The receiver MUST reject the request if the source URL is the same as the target URL.
+
+func TestWebmentionSameTargetAndSource(t *testing.T) {
+
+	repo := getTestRepo()
+	user, _ := repo.CreateUser("test-1")
+	post, _ := user.CreateNewPost("post-1")
+
+	target := post.FullUrl()
+	source := post.FullUrl()
+
+	rr, err := setupWebmentionTest(repo, user, target, source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertStatus(t, rr, http.StatusBadRequest)
+}
+
+// The receiver SHOULD check that target is a valid resource for which it can accept Webmentions.
+// This check SHOULD happen synchronously to reject invalid Webmentions before more in-depth verification begins.
+// What a "valid resource" means is up to the receiver.
+func TestValidationOfTarget(t *testing.T) {
+	repo := getTestRepo()
+	user, _ := repo.CreateUser("test-1")
+	post, _ := user.CreateNewPost("post-1")
+
+	target := post.FullUrl()
+	target = target[:len(target)-1] + "invalid"
+	source := post.FullUrl()
+
+	rr, err := setupWebmentionTest(repo, user, target, source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertStatus(t, rr, http.StatusNotFound)
+}
+
+//
+// https://www.w3.org/TR/webmention/#h-webmention-verification
+//