diff --git a/alerts.go b/alerts.go
index 22d457fd8..63198aa3b 100644
--- a/alerts.go
+++ b/alerts.go
@@ -6,6 +6,8 @@ import (
 	"sort"
 
 	"github.com/gin-gonic/gin"
+	"vbom.ml/util/sortorder"
+
 	"github.com/prymitive/karma/internal/alertmanager"
 	"github.com/prymitive/karma/internal/config"
 	"github.com/prymitive/karma/internal/filters"
@@ -61,7 +63,7 @@ func countersToLabelStats(counters map[string]map[string]int) models.LabelNameSt
 		// now that we have total hits we can calculate %
 		var totalPercent int
 		for i, value := range nameStats.Values {
-			nameStats.Values[i].Percent = int(math.Round((float64(value.Hits) / float64(nameStats.Hits)) * 100.0))
+			nameStats.Values[i].Percent = int(math.Floor((float64(value.Hits) / float64(nameStats.Hits)) * 100.0))
 			totalPercent += nameStats.Values[i].Percent
 		}
 		sort.Sort(nameStats.Values)
@@ -128,17 +130,17 @@ func getUpstreams() models.AlertmanagerAPISummary {
 	return summary
 }
 
-func resolveLabelValue(name, value string) (int, bool) {
+func resolveLabelValue(name, value string) string {
 	valueReplacements, found := config.Config.Grid.Sorting.CustomValues.Labels[name]
 	if found {
 		if replacement, ok := valueReplacements[value]; ok {
-			return replacement, true
+			return replacement
 		}
 	}
-	return value, false
+	return value
 }
 
-func getGroupLabel(group *models.APIAlertGroup, label string) int {
+func getGroupLabel(group *models.APIAlertGroup, label string) string {
 	if v, found := group.Labels[label]; found {
 		return resolveLabelValue(label, v)
 	}
@@ -148,7 +150,15 @@ func getGroupLabel(group *models.APIAlertGroup, label string) int {
 	if v, found := group.Alerts[0].Labels[label]; found {
 		return resolveLabelValue(label, v)
 	}
-	return 0
+	return ""
+}
+
+func sortByStartsAt(i, j int, groups []models.APIAlertGroup, sortReverse bool) bool {
+	if sortReverse {
+		return groups[i].LatestStartsAt.After(groups[j].LatestStartsAt)
+	} else {
+		return groups[i].LatestStartsAt.Before(groups[j].LatestStartsAt)
+	}
 }
 
 func sortAlertGroups(c *gin.Context, groupsMap map[string]models.APIAlertGroup) []models.APIAlertGroup {
@@ -160,7 +170,7 @@ func sortAlertGroups(c *gin.Context, groupsMap map[string]models.APIAlertGroup)
 	}
 
 	sortReverse, found := c.GetQuery("sortReverse")
-	if !found {
+	if !found || (sortReverse != "0" && sortReverse != "1") {
 		if config.Config.Grid.Sorting.Reverse {
 			sortReverse = "1"
 		} else {
@@ -179,26 +189,56 @@ func sortAlertGroups(c *gin.Context, groupsMap map[string]models.APIAlertGroup)
 
 	switch sortOrder {
 	case "startsAt":
-		sort.SliceStable(groups, func(i, j int) bool {
-			return groups[i].LatestStartsAt.After(groups[j].LatestStartsAt)
+		sort.Slice(groups, func(i, j int) bool {
+			return sortByStartsAt(i, j, groups, sortReverse == "1")
 		})
 	case "label":
-		sort.SliceStable(groups, func(i, j int) bool {
-			return getGroupLabel(&groups[i], sortLabel) < getGroupLabel(&groups[j], sortLabel)
+		sort.Slice(groups, func(i, j int) bool {
+			vi := getGroupLabel(&groups[i], sortLabel)
+			vj := getGroupLabel(&groups[j], sortLabel)
+			if vi == "" && vj == "" {
+				// both groups lack this label, fallback to timestamp sort
+				return sortByStartsAt(i, j, groups, true)
+			}
+
+			if vi == "" {
+				// first label is missing
+				if sortReverse == "0" {
+					return false
+				} else {
+					return true
+				}
+			}
+			if vj == "" {
+				// second label is missing
+				if sortReverse == "0" {
+					return true
+				} else {
+					return false
+				}
+			}
+			if vi == vj {
+				// both labels are equal fallback to timestamp sort
+				return sortByStartsAt(i, j, groups, true)
+			}
+			// finnally return groups sorted by label
+			if sortReverse == "1" {
+				return !sortorder.NaturalLess(vi, vj)
+			} else {
+				return sortorder.NaturalLess(vi, vj)
+			}
 		})
 	default:
 		// sort alert groups so they are always returned in the same order
 		// use group ID which is unique and immutable
-		sort.SliceStable(groups, func(i, j int) bool {
-			return groups[i].ID < groups[j].ID
+		sort.Slice(groups, func(i, j int) bool {
+			if sortReverse == "1" {
+				return groups[i].ID < groups[j].ID
+			} else {
+				return groups[i].ID > groups[j].ID
+			}
 		})
 	}
 
-	if sortReverse == "1" {
-		sort.Reverse(groups)
-	}
-
 	return groups
-
-	//
 }
diff --git a/api_test.go b/api_test.go
index 41fc64cf3..15f8f6acb 100644
--- a/api_test.go
+++ b/api_test.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -9,6 +10,7 @@ import (
 	"time"
 
 	"github.com/blang/semver"
+	"github.com/google/go-cmp/cmp"
 
 	"github.com/prymitive/karma/internal/mock"
 	"github.com/prymitive/karma/internal/models"
@@ -786,17 +788,17 @@ var countsMap = models.LabelNameStatsList{
 			models.LabelValueStats{
 				Value:   "server1",
 				Hits:    2,
-				Percent: 8,
+				Percent: 9,
 			},
 			models.LabelValueStats{
 				Value:   "server2",
 				Hits:    4,
-				Percent: 18,
+				Percent: 17,
 			},
 			models.LabelValueStats{
 				Value:   "server3",
 				Hits:    2,
-				Percent: 8,
+				Percent: 9,
 			},
 			models.LabelValueStats{
 				Value:   "server4",
@@ -806,7 +808,7 @@ var countsMap = models.LabelNameStatsList{
 			models.LabelValueStats{
 				Value:   "server5",
 				Hits:    4,
-				Percent: 18,
+				Percent: 17,
 			},
 			models.LabelValueStats{
 				Value:   "server6",
@@ -837,7 +839,7 @@ var countsMap = models.LabelNameStatsList{
 	},
 	{
 		Name: "ip",
-		Hits: 8,
+		Hits: 16,
 		Values: models.LabelValueStatsList{
 			models.LabelValueStats{
 				Value:   "127.0.0.1",
@@ -1141,3 +1143,123 @@ func TestVerifyAllGroups(t *testing.T) {
 		}
 	}
 }
+
+type sortTest struct {
+	filter         string
+	sortOrder      string
+	sortLabel      string
+	sortReverse    string
+	expectedLabel  string
+	expectedValues []string
+}
+
+var sortTests = []sortTest{
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "label",
+		sortLabel:      "cluster",
+		sortReverse:    "0",
+		expectedLabel:  "cluster",
+		expectedValues: []string{"dev", "dev", "prod", "prod", "staging", "staging"},
+	},
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "label",
+		sortLabel:      "cluster",
+		sortReverse:    "1",
+		expectedLabel:  "cluster",
+		expectedValues: []string{"staging", "staging", "prod", "prod", "dev", "dev"},
+	},
+	{
+		filter:         "q=cluster=dev",
+		sortOrder:      "label",
+		sortLabel:      "cluster",
+		sortReverse:    "0",
+		expectedLabel:  "cluster",
+		expectedValues: []string{"dev", "dev", "dev", "dev"},
+	},
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "label",
+		sortLabel:      "disk",
+		sortReverse:    "0",
+		expectedLabel:  "disk",
+		expectedValues: []string{"sda", "", "", "", "", "", "", "", "", "", "", ""},
+	},
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "label",
+		sortLabel:      "disk",
+		sortReverse:    "1",
+		expectedLabel:  "disk",
+		expectedValues: []string{"", "", "", "", "", "", "", "", "", "", "", "sda"},
+	},
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "disabled",
+		sortLabel:      "",
+		sortReverse:    "0",
+		expectedLabel:  "cluster",
+		expectedValues: []string{"dev", "prod", "staging", "dev", "staging", "prod"},
+	},
+	{
+		filter:         "q=@receiver=by-cluster-service",
+		sortOrder:      "disabled",
+		sortLabel:      "",
+		sortReverse:    "1",
+		expectedLabel:  "cluster",
+		expectedValues: []string{"prod", "staging", "dev", "staging", "prod", "dev"},
+	},
+}
+
+func TestSortOrder(t *testing.T) {
+	mockConfig()
+	for _, version := range mock.ListAllMocks() {
+		t.Logf("Testing API using mock files from Alertmanager %s", version)
+		mockAlerts(version)
+		r := ginTestEngine()
+
+		for _, testCase := range sortTests {
+			uri := fmt.Sprintf(
+				"/alerts.json?sortOrder=%s&sortLabel=%s&sortReverse=%s&%s",
+				testCase.sortOrder,
+				testCase.sortLabel,
+				testCase.sortReverse,
+				testCase.filter,
+			)
+			t.Logf("Request URI: %s", uri)
+			req := httptest.NewRequest("GET", uri, nil)
+			resp := httptest.NewRecorder()
+			r.ServeHTTP(resp, req)
+			if resp.Code != http.StatusOK {
+				t.Errorf("GET /alerts.json returned status %d", resp.Code)
+			}
+
+			ur := models.AlertsResponse{}
+			err := json.Unmarshal(resp.Body.Bytes(), &ur)
+			if err != nil {
+				t.Errorf("Failed to unmarshal response: %s", err)
+			}
+
+			values := []string{}
+			for _, ag := range ur.AlertGroups {
+				v := ag.Labels[testCase.expectedLabel]
+				if v == "" {
+					v = ag.Shared.Labels[testCase.expectedLabel]
+				}
+				if v != "" {
+					values = append(values, v)
+				} else {
+					for _, alert := range ag.Alerts {
+						v = alert.Labels[testCase.expectedLabel]
+						values = append(values, v)
+					}
+				}
+			}
+
+			if diff := cmp.Diff(testCase.expectedValues, values); diff != "" {
+				t.Errorf("Incorrectly sorted values (-want +got):\n%s", diff)
+			}
+		}
+	}
+}
diff --git a/go.mod b/go.mod
index 6006fae23..7da133fed 100644
--- a/go.mod
+++ b/go.mod
@@ -19,6 +19,8 @@ require (
 	github.com/go-openapi/swag v0.19.4
 	github.com/go-openapi/validate v0.19.2
 	github.com/golangci/golangci-lint v1.17.1
+	github.com/google/go-cmp v0.3.0
+	github.com/google/pprof v0.0.0-20190723021845-34ac40c74b70 // indirect
 	github.com/hansrodtang/randomcolor v0.0.0-20160512071917-d27108b3d7a5
 	github.com/jarcoal/httpmock v1.0.4
 	github.com/mcuadros/go-gin-prometheus v0.1.1-0.20190723203314-c7374e9082f8
@@ -31,8 +33,10 @@ require (
 	github.com/spf13/pflag v1.0.3
 	github.com/spf13/viper v1.4.0
 	github.com/terinjokes/bakelite v0.2.0
+	golang.org/x/arch v0.0.0-20190312162104-788fe5ffcd8c // indirect
 	gopkg.in/go-playground/colors.v1 v1.2.0
 	gopkg.in/yaml.v2 v2.2.2
+	vbom.ml/util v0.0.0-20180919145318-efcd4e0f9787
 )
 
 replace github.com/ugorji/go v1.1.4 => github.com/ugorji/go/codec v0.0.0-20190204201341-e444a5086c43
diff --git a/go.sum b/go.sum
index c14698286..74bd691f3 100644
--- a/go.sum
+++ b/go.sum
@@ -225,6 +225,8 @@ github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5a
 github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
+github.com/google/pprof v0.0.0-20190723021845-34ac40c74b70 h1:XTnP8fJpa4Kvpw2qARB4KS9izqxPS0Sd92cDlY3uk+w=
+github.com/google/pprof v0.0.0-20190723021845-34ac40c74b70/go.mod h1:zfwlbNMJ+OItoe0UupaVj+oy1omPYYDuagoSzA8v9mc=
 github.com/google/uuid v1.0.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
 github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
@@ -427,6 +429,8 @@ go.mongodb.org/mongo-driver v1.0.3/go.mod h1:u7ryQJ+DOzQmeO7zB6MHyr8jkEQvC8vH7qL
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
+golang.org/x/arch v0.0.0-20190312162104-788fe5ffcd8c h1:Rx/HTKi09myZ25t1SOlDHmHOy/mKxNAcu0hP1oPX9qM=
+golang.org/x/arch v0.0.0-20190312162104-788fe5ffcd8c/go.mod h1:flIaEI6LNU6xOCD5PaJvn9wGP0agmIOqjrtsKGRguv4=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a h1:YX8ljsm6wXlHZO+aRz9Exqr0evNhKRNe5K/gi+zKh4U=
@@ -533,5 +537,8 @@ gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
+rsc.io/pdf v0.1.1/go.mod h1:n8OzWcQ6Sp37PL01nO98y4iUCRdTGarVfzxY20ICaU4=
 sourcegraph.com/sqs/pbtypes v0.0.0-20180604144634-d3ebe8f20ae4 h1:JPJh2pk3+X4lXAkZIk2RuE/7/FoK9maXw+TNPJhVS/c=
 sourcegraph.com/sqs/pbtypes v0.0.0-20180604144634-d3ebe8f20ae4/go.mod h1:ketZ/q3QxT9HOBeFhu6RdvsftgpsbFHBF5Cas6cDKZ0=
+vbom.ml/util v0.0.0-20180919145318-efcd4e0f9787 h1:O69FD9pJA4WUZlEwYatBEEkRWKQ5cKodWpdKTrCS/iQ=
+vbom.ml/util v0.0.0-20180919145318-efcd4e0f9787/go.mod h1:so/NYdZXCz+E3ZpW0uAoCj6uzU2+8OWDFv/HxUSs7kI=
diff --git a/internal/config/models.go b/internal/config/models.go
index 1df0acb00..1cbc845b3 100644
--- a/internal/config/models.go
+++ b/internal/config/models.go
@@ -61,7 +61,7 @@ type configSchema struct {
 			Reverse      bool
 			Label        string
 			CustomValues struct {
-				Labels map[string]map[string]int
+				Labels map[string]map[string]string
 			} `yaml:"customValues" mapstructure:"customValues"`
 		}
 	}
diff --git a/internal/models/api.go b/internal/models/api.go
index 88f227208..f6a9f7b40 100644
--- a/internal/models/api.go
+++ b/internal/models/api.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"sort"
 
+	"vbom.ml/util/sortorder"
+
 	"github.com/prymitive/karma/internal/slices"
 )
 
@@ -56,7 +58,7 @@ func (lvsl LabelValueStatsList) Swap(i, j int) {
 }
 func (lvsl LabelValueStatsList) Less(i, j int) bool {
 	if lvsl[i].Hits == lvsl[j].Hits {
-		return lvsl[i].Value > lvsl[j].Value
+		return sortorder.NaturalLess(lvsl[i].Value, lvsl[j].Value)
 	}
 	return lvsl[i].Hits > lvsl[j].Hits
 }
@@ -263,8 +265,8 @@ type GridSettings struct {
 
 // SortSettings nests all settings specific to sorting
 type SortSettings struct {
-	Grid         GridSettings              `json:"grid"`
-	ValueMapping map[string]map[string]int `json:"valueMapping"`
+	Grid         GridSettings                 `json:"grid"`
+	ValueMapping map[string]map[string]string `json:"valueMapping"`
 }
 
 type SilenceFormStripSettings struct {
diff --git a/views.go b/views.go
index 5ac5de515..8df93e159 100644
--- a/views.go
+++ b/views.go
@@ -144,7 +144,7 @@ func alerts(c *gin.Context) {
 				Reverse: config.Config.Grid.Sorting.Reverse,
 				Label:   config.Config.Grid.Sorting.Label,
 			},
-			ValueMapping: map[string]map[string]int{},
+			ValueMapping: map[string]map[string]string{},
 		},
 		StaticColorLabels:        config.Config.Labels.Color.Static,
 		AnnotationsDefaultHidden: config.Config.Annotations.Default.Hidden,
@@ -316,6 +316,7 @@ func alerts(c *gin.Context) {
 			agCopy.Hash = agCopy.ContentFingerprint()
 			apiAG := models.APIAlertGroup{AlertGroup: agCopy}
 			apiAG.DedupSharedMaps()
+			sort.Sort(apiAG.Alerts)
 			alerts[agCopy.ID] = apiAG
 			resp.TotalAlerts += len(agCopy.Alerts)
 		}