diff --git a/api/checks/api.go b/api/checks/api.go
index ff6ffee7ea2..4e749a0e693 100644
--- a/api/checks/api.go
+++ b/api/checks/api.go
@@ -166,7 +166,7 @@ func (s checksAPIImpl) CreateWPTCheckSuite(appID, installationID int64, sha stri
 
 func (s checksAPIImpl) GetWPTRepoAppInstallationIDs() (appID, installationID int64) {
 	// Production
-	if s.GetHostname() == "wpt.fyi" {
+	if s.GetOrigin().Hostname() == "wpt.fyi" {
 		return wptfyiCheckAppID, wptRepoInstallationID
 	}
 	// Default to staging
diff --git a/api/checks/mock_checks/api_mock.go b/api/checks/mock_checks/api_mock.go
index 49b68e40d73..292e3e8970b 100644
--- a/api/checks/mock_checks/api_mock.go
+++ b/api/checks/mock_checks/api_mock.go
@@ -130,18 +130,18 @@ func (mr *MockAPIMockRecorder) GetHTTPClientWithTimeout(arg0 interface{}) *gomoc
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHTTPClientWithTimeout", reflect.TypeOf((*MockAPI)(nil).GetHTTPClientWithTimeout), arg0)
 }
 
-// GetHostname mocks base method.
-func (m *MockAPI) GetHostname() string {
+// GetOrigin mocks base method.
+func (m *MockAPI) GetOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetHostname indicates an expected call of GetHostname.
-func (mr *MockAPIMockRecorder) GetHostname() *gomock.Call {
+// GetOrigin indicates an expected call of GetOrigin.
+func (mr *MockAPIMockRecorder) GetOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHostname", reflect.TypeOf((*MockAPI)(nil).GetHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetOrigin", reflect.TypeOf((*MockAPI)(nil).GetOrigin))
 }
 
 // GetResultsURL mocks base method.
@@ -244,18 +244,18 @@ func (mr *MockAPIMockRecorder) GetVersion() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersion", reflect.TypeOf((*MockAPI)(nil).GetVersion))
 }
 
-// GetVersionedHostname mocks base method.
-func (m *MockAPI) GetVersionedHostname() string {
+// GetVersionedOrigin mocks base method.
+func (m *MockAPI) GetVersionedOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetVersionedHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetVersionedOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetVersionedHostname indicates an expected call of GetVersionedHostname.
-func (mr *MockAPIMockRecorder) GetVersionedHostname() *gomock.Call {
+// GetVersionedOrigin indicates an expected call of GetVersionedOrigin.
+func (mr *MockAPIMockRecorder) GetVersionedOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedHostname", reflect.TypeOf((*MockAPI)(nil).GetVersionedHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedOrigin", reflect.TypeOf((*MockAPI)(nil).GetVersionedOrigin))
 }
 
 // GetWPTRepoAppInstallationIDs mocks base method.
diff --git a/api/checks/update.go b/api/checks/update.go
index 33a053629f7..9f2c2513c2d 100644
--- a/api/checks/update.go
+++ b/api/checks/update.go
@@ -189,9 +189,9 @@ func getDiffSummary(aeAPI shared.AppEngineAPI, diffAPI shared.DiffAPI, suite sha
 	}
 
 	diffURL := diffAPI.GetDiffURL(baseRun, headRun, &diffFilter)
-	host := aeAPI.GetHostname()
+	origin := aeAPI.GetOrigin()
 	checkState := summaries.CheckState{
-		HostName:   host,
+		HostName:   origin.Host,
 		TestRun:    &headRun,
 		Product:    checkProduct,
 		HeadSHA:    headRun.FullRevisionHash,
@@ -231,7 +231,7 @@ func getDiffSummary(aeAPI shared.AppEngineAPI, diffAPI shared.DiffAPI, suite sha
 	resultsComparison := summaries.ResultsComparison{
 		BaseRun: baseRun,
 		HeadRun: headRun,
-		HostURL: fmt.Sprintf("https://%s/", host),
+		HostURL: origin.Host,
 		DiffURL: diffURL.String(),
 	}
 	if headRun.LabelsSet().Contains(shared.PRHeadLabel) {
diff --git a/api/checks/update_test.go b/api/checks/update_test.go
index 2407cff06d7..ec9e3da6ba2 100644
--- a/api/checks/update_test.go
+++ b/api/checks/update_test.go
@@ -31,7 +31,8 @@ func TestGetDiffSummary_Regressed(t *testing.T) {
 			aeAPI.EXPECT().Context().AnyTimes().Return(context.Background())
 			aeAPI.EXPECT().IsFeatureEnabled(onlyChangesAsRegressionsFeature).Return(enabled)
 			aeAPI.EXPECT().IsFeatureEnabled(failChecksOnRegressionFeature).Return(false)
-			aeAPI.EXPECT().GetHostname()
+			origin, _ := url.Parse("https://some-origin.com")
+			aeAPI.EXPECT().GetOrigin().Return(origin)
 			diffAPI := sharedtest.NewMockDiffAPI(mockCtrl)
 			diffAPI.EXPECT().GetRunsDiff(before, after, sharedtest.SameDiffFilter("ADC"), gomock.Any()).Return(runDiff, nil)
 			if enabled {
@@ -49,6 +50,7 @@ func TestGetDiffSummary_Regressed(t *testing.T) {
 			_, ok := summary.(summaries.Regressed)
 			assert.True(t, ok)
 			assert.Equal(t, suite.PRNumbers, summary.GetCheckState().PRNumbers)
+			assert.Equal(t, "some-origin.com", summary.GetCheckState().HostName)
 		})
 	}
 	testSummary(false)
@@ -68,7 +70,10 @@ func TestGetDiffSummary_Completed(t *testing.T) {
 	aeAPI.EXPECT().Context().AnyTimes().Return(context.Background())
 	aeAPI.EXPECT().IsFeatureEnabled(onlyChangesAsRegressionsFeature).Return(false)
 	aeAPI.EXPECT().IsFeatureEnabled(failChecksOnRegressionFeature).Return(false)
-	aeAPI.EXPECT().GetHostname()
+	aeAPI.EXPECT().GetOrigin().Return(&url.URL{
+		Scheme: "https",
+		Host:   "example.com",
+	})
 	diffAPI := sharedtest.NewMockDiffAPI(mockCtrl)
 	diffAPI.EXPECT().GetRunsDiff(before, after, gomock.Any(), gomock.Any()).Return(runDiff, nil)
 	diffURL, _ := url.Parse("https://wpt.fyi/results?diff")
@@ -83,6 +88,7 @@ func TestGetDiffSummary_Completed(t *testing.T) {
 	_, ok := summary.(summaries.Completed)
 	assert.True(t, ok)
 	assert.Equal(t, suite.PRNumbers, summary.GetCheckState().PRNumbers)
+	assert.Equal(t, "example.com", summary.GetCheckState().HostName)
 }
 
 func getBeforeAndAfterRuns() (before, after shared.TestRun) {
diff --git a/api/receiver/client/client.go b/api/receiver/client/client.go
index 1e51b8a899e..6da3046ffdd 100644
--- a/api/receiver/client/client.go
+++ b/api/receiver/client/client.go
@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"path"
 	"strings"
 	"time"
 
@@ -67,8 +68,10 @@ func (c client) CreateRun(
 		payload.Add("labels", strings.Join(labels, ","))
 	}
 	// Ensure we call back to this appengine version instance.
-	host := c.aeAPI.GetVersionedHostname()
-	payload.Add("callback_url", fmt.Sprintf("https://%s/api/results/create", host))
+	u := c.aeAPI.GetVersionedOrigin()
+	u.Path = path.Join(u.Path, "/api/results/create")
+
+	payload.Add("callback_url", u.String())
 
 	uploadURL := c.aeAPI.GetResultsUploadURL()
 	req, err := http.NewRequest("POST", uploadURL.String(), strings.NewReader(payload.Encode()))
diff --git a/api/receiver/client/client_test.go b/api/receiver/client/client_test.go
index 7bc217a309a..e0f3c4fa0ae 100644
--- a/api/receiver/client/client_test.go
+++ b/api/receiver/client/client_test.go
@@ -29,6 +29,7 @@ func TestCreateRun(t *testing.T) {
 		assert.Nil(t, r.ParseForm())
 		assert.Equal(t, []string{"https://wpt.fyi/results.json.gz"}, r.PostForm["result_url"])
 		assert.Equal(t, []string{"https://wpt.fyi/screenshots.db.gz"}, r.PostForm["screenshot_url"])
+		assert.Equal(t, []string{"http://localhost:8080/api/results/create"}, r.PostForm["callback_url"])
 		assert.Equal(t, "foo,bar", r.PostForm.Get("labels"))
 		w.Write([]byte("OK"))
 		visited = true
@@ -41,7 +42,9 @@ func TestCreateRun(t *testing.T) {
 	defer mockC.Finish()
 	aeAPI := sharedtest.NewMockAppEngineAPI(mockC)
 	gomock.InOrder(
-		aeAPI.EXPECT().GetVersionedHostname().Return("localhost:8080"),
+		aeAPI.EXPECT().GetVersionedOrigin().Return(&url.URL{
+			Scheme: "http",
+			Host:   "localhost:8080"}),
 		aeAPI.EXPECT().GetResultsUploadURL().Return(serverURL),
 		aeAPI.EXPECT().GetHTTPClientWithTimeout(UploadTimeout).Return(server.Client()),
 	)
diff --git a/api/receiver/mock_receiver/api_mock.go b/api/receiver/mock_receiver/api_mock.go
index f963887af3e..388cf57532c 100644
--- a/api/receiver/mock_receiver/api_mock.go
+++ b/api/receiver/mock_receiver/api_mock.go
@@ -112,18 +112,18 @@ func (mr *MockAPIMockRecorder) GetHTTPClientWithTimeout(arg0 interface{}) *gomoc
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHTTPClientWithTimeout", reflect.TypeOf((*MockAPI)(nil).GetHTTPClientWithTimeout), arg0)
 }
 
-// GetHostname mocks base method.
-func (m *MockAPI) GetHostname() string {
+// GetOrigin mocks base method.
+func (m *MockAPI) GetOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetHostname indicates an expected call of GetHostname.
-func (mr *MockAPIMockRecorder) GetHostname() *gomock.Call {
+// GetOrigin indicates an expected call of GetOrigin.
+func (mr *MockAPIMockRecorder) GetOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHostname", reflect.TypeOf((*MockAPI)(nil).GetHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetOrigin", reflect.TypeOf((*MockAPI)(nil).GetOrigin))
 }
 
 // GetResultsURL mocks base method.
@@ -211,18 +211,18 @@ func (mr *MockAPIMockRecorder) GetVersion() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersion", reflect.TypeOf((*MockAPI)(nil).GetVersion))
 }
 
-// GetVersionedHostname mocks base method.
-func (m *MockAPI) GetVersionedHostname() string {
+// GetVersionedOrigin mocks base method.
+func (m *MockAPI) GetVersionedOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetVersionedHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetVersionedOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetVersionedHostname indicates an expected call of GetVersionedHostname.
-func (mr *MockAPIMockRecorder) GetVersionedHostname() *gomock.Call {
+// GetVersionedOrigin indicates an expected call of GetVersionedOrigin.
+func (mr *MockAPIMockRecorder) GetVersionedOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedHostname", reflect.TypeOf((*MockAPI)(nil).GetVersionedHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedOrigin", reflect.TypeOf((*MockAPI)(nil).GetVersionedOrigin))
 }
 
 // IsAdmin mocks base method.
diff --git a/api/screenshot/cache.go b/api/screenshot/cache.go
index f512b69c0e9..918761ace2b 100644
--- a/api/screenshot/cache.go
+++ b/api/screenshot/cache.go
@@ -63,7 +63,7 @@ func uploadScreenshotHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	bucketName := "wptd-screenshots-staging"
-	if aeAPI.GetHostname() == "wpt.fyi" {
+	if aeAPI.GetOrigin().Hostname() == "wpt.fyi" {
 		bucketName = "wptd-screenshots"
 	}
 	bucket := gcs.Bucket(bucketName)
diff --git a/api/screenshot_redirect_handler.go b/api/screenshot_redirect_handler.go
index ffcfc6d555c..2989a18969d 100644
--- a/api/screenshot_redirect_handler.go
+++ b/api/screenshot_redirect_handler.go
@@ -26,7 +26,7 @@ func apiScreenshotRedirectHandler(w http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
 	aeAPI := shared.NewAppEngineAPI(ctx)
 	bucket := "wptd-screenshots-staging"
-	if aeAPI.GetHostname() == "wpt.fyi" {
+	if aeAPI.GetOrigin().Hostname() == "wpt.fyi" {
 		bucket = "wptd-screenshots"
 	}
 	url := fmt.Sprintf("https://storage.googleapis.com/%s/%s.png", bucket, shot)
diff --git a/api/taskcluster/webhook_test.go b/api/taskcluster/webhook_test.go
index bc89bf71fe5..489e2facdd8 100644
--- a/api/taskcluster/webhook_test.go
+++ b/api/taskcluster/webhook_test.go
@@ -34,6 +34,16 @@ func strPtr(s string) *string {
 	return &s
 }
 
+func testOrigin() *url.URL {
+	// Because these tests call the function multiple times, we need to use
+	// DoAndReturn and pass this function for the mock assertion.
+	// Without it, it will append the path to the same pointer
+	u := new(url.URL)
+	u.Scheme = "http"
+	u.Host = "localhost:8080"
+	return u
+}
+
 func TestShouldProcessStatus_states(t *testing.T) {
 	status := tc.StatusEventPayload{}
 	status.State = strPtr("success")
@@ -250,6 +260,8 @@ func TestCreateAllRuns_success(t *testing.T) {
 	var requested uint32
 	requested = 0
 	handler := func(w http.ResponseWriter, r *http.Request) {
+		assert.Nil(t, r.ParseForm())
+		assert.Equal(t, []string{"http://localhost:8080/api/results/create"}, r.PostForm["callback_url"])
 		atomic.AddUint32(&requested, 1)
 		w.Write([]byte("OK"))
 	}
@@ -261,7 +273,8 @@ func TestCreateAllRuns_success(t *testing.T) {
 	mockC := gomock.NewController(t)
 	defer mockC.Finish()
 	aeAPI := sharedtest.NewMockAppEngineAPI(mockC)
-	aeAPI.EXPECT().GetVersionedHostname().AnyTimes().Return("localhost:8080")
+
+	aeAPI.EXPECT().GetVersionedOrigin().MinTimes(1).DoAndReturn(testOrigin)
 	aeAPI.EXPECT().GetHTTPClientWithTimeout(uc.UploadTimeout).AnyTimes().Return(server.Client())
 	aeAPI.EXPECT().GetResultsUploadURL().AnyTimes().Return(serverURL)
 
@@ -308,6 +321,8 @@ func TestCreateAllRuns_one_error(t *testing.T) {
 	var requested uint32
 	requested = 0
 	handler := func(w http.ResponseWriter, r *http.Request) {
+		assert.Nil(t, r.ParseForm())
+		assert.Equal(t, []string{"http://localhost:8080/api/results/create"}, r.PostForm["callback_url"])
 		if atomic.CompareAndSwapUint32(&requested, 0, 1) {
 			w.Write([]byte("OK"))
 		} else if atomic.CompareAndSwapUint32(&requested, 1, 2) {
@@ -324,7 +339,7 @@ func TestCreateAllRuns_one_error(t *testing.T) {
 	sha := "abcdef1234abcdef1234abcdef1234abcdef1234"
 
 	aeAPI := sharedtest.NewMockAppEngineAPI(mockC)
-	aeAPI.EXPECT().GetVersionedHostname().MinTimes(1).Return("localhost:8080")
+	aeAPI.EXPECT().GetVersionedOrigin().MinTimes(1).DoAndReturn(testOrigin)
 	aeAPI.EXPECT().GetHTTPClientWithTimeout(uc.UploadTimeout).Times(2).Return(server.Client())
 	serverURL, _ := url.Parse(server.URL)
 	aeAPI.EXPECT().GetResultsUploadURL().AnyTimes().Return(serverURL)
@@ -349,6 +364,8 @@ func TestCreateAllRuns_one_error(t *testing.T) {
 
 func TestCreateAllRuns_all_errors(t *testing.T) {
 	handler := func(w http.ResponseWriter, r *http.Request) {
+		assert.Nil(t, r.ParseForm())
+		assert.Equal(t, []string{"http://localhost:8080/api/results/create"}, r.PostForm["callback_url"])
 		time.Sleep(time.Second * 2)
 	}
 	server := httptest.NewServer(http.HandlerFunc(handler))
@@ -359,7 +376,7 @@ func TestCreateAllRuns_all_errors(t *testing.T) {
 	sha := "abcdef1234abcdef1234abcdef1234abcdef1234"
 
 	aeAPI := sharedtest.NewMockAppEngineAPI(mockC)
-	aeAPI.EXPECT().GetVersionedHostname().MinTimes(1).Return("localhost:8080")
+	aeAPI.EXPECT().GetVersionedOrigin().MinTimes(1).DoAndReturn(testOrigin)
 	// Give a very short timeout (instead of the asked 1min) to make tests faster.
 	aeAPI.EXPECT().GetHTTPClientWithTimeout(uc.UploadTimeout).MinTimes(1).Return(&http.Client{Timeout: time.Microsecond})
 	serverURL, _ := url.Parse(server.URL)
@@ -383,6 +400,8 @@ func TestCreateAllRuns_all_errors(t *testing.T) {
 
 func TestCreateAllRuns_pr_labels_exclude_master(t *testing.T) {
 	handler := func(w http.ResponseWriter, r *http.Request) {
+		assert.Nil(t, r.ParseForm())
+		assert.Equal(t, []string{"http://localhost:8080/api/results/create"}, r.PostForm["callback_url"])
 		// We should not see a master label here, even though we
 		// specify one in the call to tc.CreateAllRuns.
 		defer r.Body.Close()
@@ -398,7 +417,7 @@ func TestCreateAllRuns_pr_labels_exclude_master(t *testing.T) {
 	mockC := gomock.NewController(t)
 	defer mockC.Finish()
 	aeAPI := sharedtest.NewMockAppEngineAPI(mockC)
-	aeAPI.EXPECT().GetVersionedHostname().AnyTimes().Return("localhost:8080")
+	aeAPI.EXPECT().GetVersionedOrigin().AnyTimes().DoAndReturn(testOrigin)
 	aeAPI.EXPECT().GetHTTPClientWithTimeout(uc.UploadTimeout).AnyTimes().Return(server.Client())
 	aeAPI.EXPECT().GetResultsUploadURL().AnyTimes().Return(serverURL)
 
diff --git a/shared/appengine.go b/shared/appengine.go
index 9742c8df7a6..c141cd172a0 100644
--- a/shared/appengine.go
+++ b/shared/appengine.go
@@ -13,6 +13,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"path"
 	"strings"
 	"time"
 
@@ -175,16 +176,16 @@ type AppEngineAPI interface {
 
 	// GetVersion returns the version name for the current environment.
 	GetVersion() string
-	// GetHostname returns the canonical hostname for the current AppEngine
-	// project, i.e. staging.wpt.fyi or wpt.fyi.
-	GetHostname() string
-	// GetVersionedHostname returns the AppEngine hostname for the current
+	// GetOrigin returns the canonical origin for the current AppEngine
+	// project, i.e. [https|http]://staging.wpt.fyi or [https|http]://wpt.fyi.
+	GetOrigin() *url.URL
+	// GetVersionedOrigin returns the AppEngine origin for the current
 	// version of the default service, i.e.,
-	//   VERSION-dot-wptdashboard{,-staging}.REGION.r.appspot.com.
+	//   [https|http]://VERSION-dot-wptdashboard{,-staging}.REGION.r.appspot.com.
 	// Note: if the default service does not have the current version,
 	// AppEngine routing will find a version according to traffic split.
 	// https://cloud.google.com/appengine/docs/standard/go/how-requests-are-routed#soft_routing
-	GetVersionedHostname() string
+	GetVersionedOrigin() *url.URL
 	// GetServiceHostname returns the AppEngine hostname for the current
 	// version of the given service, i.e.,
 	//   VERSION-dot-SERVICE-dot-wptdashboard{,-staging}.REGION.r.appspot.com.
@@ -302,6 +303,26 @@ func (a appEngineAPIImpl) GetUploader(uploader string) (Uploader, error) {
 	return GetUploader(m, uploader)
 }
 
+func (a appEngineAPIImpl) GetOrigin() *url.URL {
+	u := new(url.URL)
+	u.Scheme = a.getScheme()
+	u.Host = a.GetHostname()
+	return u
+}
+func (a appEngineAPIImpl) GetVersionedOrigin() *url.URL {
+	u := new(url.URL)
+	u.Scheme = a.getScheme()
+	u.Host = a.GetVersionedHostname()
+	return u
+}
+
+func (a appEngineAPIImpl) getScheme() string {
+	if runtimeIdentity.application != nil {
+		return "https"
+	}
+	return "http"
+}
+
 func (a appEngineAPIImpl) GetHostname() string {
 	if runtimeIdentity.AppID == "wptdashboard" {
 		return "wpt.fyi"
@@ -335,15 +356,16 @@ func (a appEngineAPIImpl) GetServiceHostname(service string) string {
 }
 
 func (a appEngineAPIImpl) GetResultsURL(filter TestRunFilter) *url.URL {
-	return getURL(a.GetHostname(), "/results/", filter)
+	return getURL(*a.GetOrigin(), "/results/", filter)
 }
 
 func (a appEngineAPIImpl) GetRunsURL(filter TestRunFilter) *url.URL {
-	return getURL(a.GetHostname(), "/runs", filter)
+	return getURL(*a.GetOrigin(), "/runs", filter)
 }
 
 func (a appEngineAPIImpl) GetResultsUploadURL() *url.URL {
-	result, _ := url.Parse(fmt.Sprintf("https://%s%s", a.GetVersionedHostname(), "/api/results/upload"))
+	result := a.GetVersionedOrigin()
+	result.Path = path.Join(result.Path, "/api/results/upload")
 	return result
 }
 
@@ -372,10 +394,10 @@ func (a appEngineAPIImpl) ScheduleTask(queueName, taskName, target string, param
 	return createdTaskName, nil
 }
 
-func getURL(host, path string, filter TestRunFilter) *url.URL {
-	detailsURL, _ := url.Parse(fmt.Sprintf("https://%s%s", host, path))
-	detailsURL.RawQuery = filter.ToQuery().Encode()
-	return detailsURL
+func getURL(origin url.URL, inputPath string, filter TestRunFilter) *url.URL {
+	origin.Path += path.Join(origin.Path, inputPath)
+	origin.RawQuery = filter.ToQuery().Encode()
+	return &origin
 }
 
 func createTaskRequest(queueName, taskName, target string, params url.Values) (taskPrefix string, req *taskspb.CreateTaskRequest) {
diff --git a/shared/run_diff.go b/shared/run_diff.go
index e23167440d8..4233cc5a70d 100644
--- a/shared/run_diff.go
+++ b/shared/run_diff.go
@@ -16,6 +16,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"path"
 	"strings"
 	"time"
 
@@ -48,7 +49,8 @@ func NewDiffAPI(ctx context.Context) DiffAPI {
 }
 
 func (d diffAPIImpl) GetDiffURL(before, after TestRun, diffFilter *DiffFilterParam) *url.URL {
-	detailsURL, _ := url.Parse(fmt.Sprintf("https://%s/results/", d.aeAPI.GetHostname()))
+	detailsURL := d.aeAPI.GetOrigin()
+	detailsURL.Path = path.Join(detailsURL.Path, "/results/")
 	query := detailsURL.Query()
 	query.Add("run_id", fmt.Sprintf("%v", before.ID))
 	query.Add("run_id", fmt.Sprintf("%v", after.ID))
@@ -380,7 +382,8 @@ func (d diffAPIImpl) GetRunsDiff(before, after TestRun, filter DiffFilterParam,
 }
 
 func (d diffAPIImpl) getRunsDiffFromSearchCache(before, after TestRun, filter DiffFilterParam, paths mapset.Set) (diff RunDiff, err error) {
-	diffURL, _ := url.Parse(fmt.Sprintf("https://%s/api/search", d.aeAPI.GetVersionedHostname()))
+	diffURL := d.aeAPI.GetVersionedOrigin()
+	diffURL.Path = path.Join(diffURL.Path, "/api/search")
 	query := diffURL.Query()
 	query.Set("diff", "")
 	query.Set("filter", filter.String())
diff --git a/shared/sharedtest/appengine_mock.go b/shared/sharedtest/appengine_mock.go
index 640d8316a4f..97fc07e56fd 100644
--- a/shared/sharedtest/appengine_mock.go
+++ b/shared/sharedtest/appengine_mock.go
@@ -96,18 +96,18 @@ func (mr *MockAppEngineAPIMockRecorder) GetHTTPClientWithTimeout(arg0 interface{
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHTTPClientWithTimeout", reflect.TypeOf((*MockAppEngineAPI)(nil).GetHTTPClientWithTimeout), arg0)
 }
 
-// GetHostname mocks base method.
-func (m *MockAppEngineAPI) GetHostname() string {
+// GetOrigin mocks base method.
+func (m *MockAppEngineAPI) GetOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetHostname indicates an expected call of GetHostname.
-func (mr *MockAppEngineAPIMockRecorder) GetHostname() *gomock.Call {
+// GetOrigin indicates an expected call of GetOrigin.
+func (mr *MockAppEngineAPIMockRecorder) GetOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetHostname", reflect.TypeOf((*MockAppEngineAPI)(nil).GetHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetOrigin", reflect.TypeOf((*MockAppEngineAPI)(nil).GetOrigin))
 }
 
 // GetResultsURL mocks base method.
@@ -195,18 +195,18 @@ func (mr *MockAppEngineAPIMockRecorder) GetVersion() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersion", reflect.TypeOf((*MockAppEngineAPI)(nil).GetVersion))
 }
 
-// GetVersionedHostname mocks base method.
-func (m *MockAppEngineAPI) GetVersionedHostname() string {
+// GetVersionedOrigin mocks base method.
+func (m *MockAppEngineAPI) GetVersionedOrigin() *url.URL {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetVersionedHostname")
-	ret0, _ := ret[0].(string)
+	ret := m.ctrl.Call(m, "GetVersionedOrigin")
+	ret0, _ := ret[0].(*url.URL)
 	return ret0
 }
 
-// GetVersionedHostname indicates an expected call of GetVersionedHostname.
-func (mr *MockAppEngineAPIMockRecorder) GetVersionedHostname() *gomock.Call {
+// GetVersionedOrigin indicates an expected call of GetVersionedOrigin.
+func (mr *MockAppEngineAPIMockRecorder) GetVersionedOrigin() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedHostname", reflect.TypeOf((*MockAppEngineAPI)(nil).GetVersionedHostname))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetVersionedOrigin", reflect.TypeOf((*MockAppEngineAPI)(nil).GetVersionedOrigin))
 }
 
 // IsFeatureEnabled mocks base method.
diff --git a/webapp/admin_handler.go b/webapp/admin_handler.go
index 71ec57946f2..27bb7e9695d 100644
--- a/webapp/admin_handler.go
+++ b/webapp/admin_handler.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"path"
 
 	"github.com/web-platform-tests/wpt.fyi/shared"
 )
@@ -51,10 +52,13 @@ func showAdminUploadForm(a shared.AppEngineAPI, acl shared.GitHubAccessControl,
 		return
 	}
 
+	u := a.GetVersionedOrigin()
+	u.Path = path.Join(u.Path, "/api/results/create")
+
 	data := struct {
 		CallbackURL string
 	}{
-		CallbackURL: fmt.Sprintf("https://%s/api/results/create", a.GetVersionedHostname()),
+		CallbackURL: u.String(),
 	}
 	// We don't need user info in this template.
 	RenderTemplate(w, nil, "admin_upload.html", data)
@@ -84,7 +88,7 @@ func handleAdminFlags(a shared.AppEngineAPI, ds shared.Datastore, acl shared.Git
 		data := struct {
 			Host string
 		}{
-			Host: a.GetHostname(),
+			Host: a.GetOrigin().Host,
 		}
 		// We don't need user info in this template.
 		RenderTemplate(w, nil, "admin_flags.html", data)
diff --git a/webapp/analyzer_handler.go b/webapp/analyzer_handler.go
index bcc06b55ff8..94d12af30e3 100644
--- a/webapp/analyzer_handler.go
+++ b/webapp/analyzer_handler.go
@@ -29,7 +29,7 @@ func analyzerHandler(w http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
 	aeAPI := shared.NewAppEngineAPI(ctx)
 	bucket := "wptd-screenshots-staging"
-	if aeAPI.GetHostname() == "wpt.fyi" {
+	if aeAPI.GetOrigin().Hostname() == "wpt.fyi" {
 		bucket = "wptd-screenshots"
 	}