diff --git a/cmd/cli/cli.go b/cmd/cli/cli.go
index d07c145..3f606b7 100644
--- a/cmd/cli/cli.go
+++ b/cmd/cli/cli.go
@@ -1489,22 +1489,24 @@ func processNoConfigFlags(noConfigStart bool) {
 		return endpoint, typ
 	}
 	pEndpoint, pType := endpointAndTyp(primaryUpstream)
-	upstream := map[string]*ctrld.UpstreamConfig{
-		"0": {
-			Name:     pEndpoint,
-			Endpoint: pEndpoint,
-			Type:     pType,
-			Timeout:  5000,
-		},
+	puc := &ctrld.UpstreamConfig{
+		Name:     pEndpoint,
+		Endpoint: pEndpoint,
+		Type:     pType,
+		Timeout:  5000,
 	}
+	puc.Init()
+	upstream := map[string]*ctrld.UpstreamConfig{"0": puc}
 	if secondaryUpstream != "" {
 		sEndpoint, sType := endpointAndTyp(secondaryUpstream)
-		upstream["1"] = &ctrld.UpstreamConfig{
+		suc := &ctrld.UpstreamConfig{
 			Name:     sEndpoint,
 			Endpoint: sEndpoint,
 			Type:     sType,
 			Timeout:  5000,
 		}
+		suc.Init()
+		upstream["1"] = suc
 		rules := make([]ctrld.Rule, 0, len(domains))
 		for _, domain := range domains {
 			rules = append(rules, ctrld.Rule{domain: []string{"upstream.1"}})
diff --git a/config.go b/config.go
index 6c66f62..3f9b2f8 100644
--- a/config.go
+++ b/config.go
@@ -65,6 +65,7 @@ const (
 	endpointPrefixHTTPS = "https://"
 	endpointPrefixQUIC  = "quic://"
 	endpointPrefixH3    = "h3://"
+	endpointPrefixSdns  = "sdns://"
 )
 
 var (
@@ -233,7 +234,7 @@ type NetworkConfig struct {
 // UpstreamConfig specifies configuration for upstreams that ctrld will forward requests to.
 type UpstreamConfig struct {
 	Name        string `mapstructure:"name" toml:"name,omitempty"`
-	Type        string `mapstructure:"type" toml:"type,omitempty" validate:"oneof=doh doh3 dot doq os legacy sdns"`
+	Type        string `mapstructure:"type" toml:"type,omitempty" validate:"oneof=doh doh3 dot doq os legacy sdns ''"`
 	Endpoint    string `mapstructure:"endpoint" toml:"endpoint,omitempty"`
 	BootstrapIP string `mapstructure:"bootstrap_ip" toml:"bootstrap_ip,omitempty"`
 	Domain      string `mapstructure:"-" toml:"-"`
@@ -687,6 +688,9 @@ func (uc *UpstreamConfig) netForDNSType(dnsType uint16) (string, string) {
 
 // initDoHScheme initializes the endpoint scheme for DoH/DoH3 upstream if not present.
 func (uc *UpstreamConfig) initDoHScheme() {
+	if strings.HasPrefix(uc.Endpoint, endpointPrefixH3) && uc.Type == "" {
+		uc.Type = ResolverTypeDOH3
+	}
 	switch uc.Type {
 	case ResolverTypeDOH:
 	case ResolverTypeDOH3:
@@ -703,6 +707,9 @@ func (uc *UpstreamConfig) initDoHScheme() {
 
 // initDnsStamps initializes upstream config based on encoded DNS Stamps Endpoint.
 func (uc *UpstreamConfig) initDnsStamps() error {
+	if strings.HasPrefix(uc.Endpoint, endpointPrefixSdns) && uc.Type == "" {
+		uc.Type = ResolverTypeSDNS
+	}
 	if uc.Type != ResolverTypeSDNS {
 		return nil
 	}
@@ -794,6 +801,12 @@ func upstreamConfigStructLevelValidation(sl validator.StructLevel) {
 		return
 	}
 
+	// Empty type is ok only for endpoints starts with "h3://" and "sdns://".
+	if uc.Type == "" && !strings.HasPrefix(uc.Endpoint, endpointPrefixH3) && !strings.HasPrefix(uc.Endpoint, endpointPrefixSdns) {
+		sl.ReportError(uc.Endpoint, "type", "type", "oneof", "doh doh3 dot doq os legacy sdns")
+		return
+	}
+
 	// initDoHScheme/initDnsStamps may change upstreams information,
 	// so restoring changed values after validation to keep original one.
 	defer func(ep, typ string) {
@@ -835,6 +848,7 @@ func defaultPortFor(typ string) string {
 // - If endpoint starts with "https://" -> ResolverTypeDOH
 // - If endpoint starts with "quic://" -> ResolverTypeDOQ
 // - If endpoint starts with "h3://" -> ResolverTypeDOH3
+// - If endpoint starts with "sdns://" -> ResolverTypeSDNS
 // - For anything else -> ResolverTypeDOT
 func ResolverTypeFromEndpoint(endpoint string) string {
 	switch {
@@ -844,6 +858,8 @@ func ResolverTypeFromEndpoint(endpoint string) string {
 		return ResolverTypeDOQ
 	case strings.HasPrefix(endpoint, endpointPrefixH3):
 		return ResolverTypeDOH3
+	case strings.HasPrefix(endpoint, endpointPrefixSdns):
+		return ResolverTypeSDNS
 	}
 	host := endpoint
 	if strings.Contains(endpoint, ":") {
diff --git a/config_internal_test.go b/config_internal_test.go
index 41edd32..7b09da3 100644
--- a/config_internal_test.go
+++ b/config_internal_test.go
@@ -200,6 +200,26 @@ func TestUpstreamConfig_Init(t *testing.T) {
 				u:           u1,
 			},
 		},
+		{
+			"h3 without type",
+			&UpstreamConfig{
+				Name:        "doh3",
+				Endpoint:    "h3://example.com",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+			},
+			&UpstreamConfig{
+				Name:        "doh3",
+				Type:        "doh3",
+				Endpoint:    "https://example.com",
+				BootstrapIP: "",
+				Domain:      "example.com",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+				u:           u1,
+			},
+		},
 		{
 			"sdns -> doh",
 			&UpstreamConfig{
@@ -285,6 +305,26 @@ func TestUpstreamConfig_Init(t *testing.T) {
 				IPStack:     IpStackBoth,
 			},
 		},
+		{
+			"sdns without type",
+			&UpstreamConfig{
+				Name:        "sdns",
+				Endpoint:    "sdns://AAcAAAAAAAAACjc2Ljc2LjIuMTE",
+				BootstrapIP: "",
+				Domain:      "",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+			},
+			&UpstreamConfig{
+				Name:        "sdns",
+				Type:        "legacy",
+				Endpoint:    "76.76.2.11:53",
+				BootstrapIP: "76.76.2.11",
+				Domain:      "76.76.2.11",
+				Timeout:     0,
+				IPStack:     IpStackBoth,
+			},
+		},
 	}
 
 	for _, tc := range tests {
diff --git a/config_test.go b/config_test.go
index c1ffeb4..a20b33c 100644
--- a/config_test.go
+++ b/config_test.go
@@ -107,6 +107,9 @@ func TestConfigValidation(t *testing.T) {
 		{"invalid doh/doh3 endpoint", configWithInvalidDoHEndpoint(t), true},
 		{"invalid client id pref", configWithInvalidClientIDPref(t), true},
 		{"doh endpoint without scheme", dohUpstreamEndpointWithoutScheme(t), false},
+		{"doh endpoint without type", dohUpstreamEndpointWithoutType(t), true},
+		{"doh3 endpoint without type", doh3UpstreamEndpointWithoutType(t), false},
+		{"sdns endpoint without type", sdnsUpstreamEndpointWithoutType(t), false},
 		{"maximum number of flush cache domains", configWithInvalidFlushCacheDomain(t), true},
 	}
 
@@ -194,6 +197,27 @@ func dohUpstreamEndpointWithoutScheme(t *testing.T) *ctrld.Config {
 	return cfg
 }
 
+func dohUpstreamEndpointWithoutType(t *testing.T) *ctrld.Config {
+	cfg := defaultConfig(t)
+	cfg.Upstream["0"].Endpoint = "https://freedns.controld.com/p1"
+	cfg.Upstream["0"].Type = ""
+	return cfg
+}
+
+func doh3UpstreamEndpointWithoutType(t *testing.T) *ctrld.Config {
+	cfg := defaultConfig(t)
+	cfg.Upstream["0"].Endpoint = "h3://freedns.controld.com/p1"
+	cfg.Upstream["0"].Type = ""
+	return cfg
+}
+
+func sdnsUpstreamEndpointWithoutType(t *testing.T) *ctrld.Config {
+	cfg := defaultConfig(t)
+	cfg.Upstream["0"].Endpoint = "sdns://AgMAAAAAAAAACjc2Ljc2LjIuMTEAFGZyZWVkbnMuY29udHJvbGQuY29tAy9wMQ"
+	cfg.Upstream["0"].Type = ""
+	return cfg
+}
+
 func invalidUpstreamTimeout(t *testing.T) *ctrld.Config {
 	cfg := defaultConfig(t)
 	cfg.Upstream["0"].Timeout = -1