diff --git a/internal/home/config.go b/internal/home/config.go
index 810ec24e..8ddb691d 100644
--- a/internal/home/config.go
+++ b/internal/home/config.go
@@ -162,6 +162,10 @@ type configuration struct {
 	// SchemaVersion is the version of the configuration schema.  See
 	// [configmigrate.LastSchemaVersion].
 	SchemaVersion uint `yaml:"schema_version"`
+
+	// UnsafeCustomUpdateIndexURL is the URL to the custom update index.  It's
+	// only used in testing purposes and should not be used in release.
+	UnsafeCustomUpdateIndexURL bool `yaml:"unsafe_custom_update_index_url,omitempty"`
 }
 
 // httpConfig is a block with HTTP configuration params.
diff --git a/internal/home/controlupdate.go b/internal/home/controlupdate.go
index 50a1a6f3..acf3e0dd 100644
--- a/internal/home/controlupdate.go
+++ b/internal/home/controlupdate.go
@@ -77,28 +77,28 @@ func (web *webAPI) requestVersionInfo(resp *versionResponse, recheck bool) (err
 	updater := web.conf.updater
 	for i := 0; i != 3; i++ {
 		resp.VersionInfo, err = updater.VersionInfo(recheck)
-		if err != nil {
-			var terr temporaryError
-			if errors.As(err, &terr) && terr.Temporary() {
-				// Temporary network error.  This case may happen while we're
-				// restarting our DNS server.  Log and sleep for some time.
-				//
-				// See https://github.com/AdguardTeam/AdGuardHome/issues/934.
-				d := time.Duration(i) * time.Second
-				log.Info("update: temp net error: %q; sleeping for %s and retrying", err, d)
-				time.Sleep(d)
+		if err == nil {
+			return nil
+		}
 
-				continue
-			}
+		var terr temporaryError
+		if errors.As(err, &terr) && terr.Temporary() {
+			// Temporary network error.  This case may happen while we're
+			// restarting our DNS server.  Log and sleep for some time.
+			//
+			// See https://github.com/AdguardTeam/AdGuardHome/issues/934.
+			d := time.Duration(i) * time.Second
+			log.Info("update: temp net error: %q; sleeping for %s and retrying", err, d)
+			time.Sleep(d)
+
+			continue
 		}
 
 		break
 	}
 
 	if err != nil {
-		vcu := updater.VersionCheckURL()
-
-		return fmt.Errorf("getting version info from %s: %w", vcu, err)
+		return fmt.Errorf("getting version info: %w", err)
 	}
 
 	return nil
diff --git a/internal/home/home.go b/internal/home/home.go
index 4c2771e4..d6f11489 100644
--- a/internal/home/home.go
+++ b/internal/home/home.go
@@ -604,29 +604,9 @@ func run(opts options, clientBuildFS fs.FS, done chan struct{}) {
 	execPath, err := os.Executable()
 	fatalOnError(errors.Annotate(err, "getting executable path: %w"))
 
-	u := &url.URL{
-		Scheme: urlutil.SchemeHTTPS,
-		// TODO(a.garipov): Make configurable.
-		Host: "static.adtidy.org",
-		Path: path.Join("adguardhome", version.Channel(), "version.json"),
-	}
-
 	confPath := configFilePath()
-	log.Debug("using config path %q for updater", confPath)
 
-	upd := updater.NewUpdater(&updater.Config{
-		Client:          config.Filtering.HTTPClient,
-		Version:         version.Version(),
-		Channel:         version.Channel(),
-		GOARCH:          runtime.GOARCH,
-		GOOS:            runtime.GOOS,
-		GOARM:           version.GOARM(),
-		GOMIPS:          version.GOMIPS(),
-		WorkDir:         Context.workDir,
-		ConfName:        confPath,
-		ExecPath:        execPath,
-		VersionCheckURL: u.String(),
-	})
+	upd := newUpdater(Context.workDir, confPath, execPath, config)
 
 	// TODO(e.burkov): This could be made earlier, probably as the option's
 	// effect.
@@ -698,6 +678,48 @@ func run(opts options, clientBuildFS fs.FS, done chan struct{}) {
 	<-done
 }
 
+// newUpdater creates a new AdGuard Home updater.
+func newUpdater(workDir, confPath, execPath string, config *configuration) (upd *updater.Updater) {
+	// envName is the name of the environment variable that can be used to
+	// override the default version check URL.
+	const envName = "ADGUARD_HOME_TEST_UPDATE_VERSION_URL"
+
+	var versionURL *url.URL
+	if version.Channel() == version.ChannelRelease || !config.UnsafeCustomUpdateIndexURL {
+		// Go on, use the default URL.
+	} else if versionURLStr, ok := os.LookupEnv(envName); ok {
+		var err error
+		versionURL, err = url.Parse(versionURLStr)
+		if err != nil {
+			log.Error(envName+" is not a valid URL: %s", err)
+		}
+	}
+
+	if versionURL == nil {
+		versionURL = &url.URL{
+			Scheme: urlutil.SchemeHTTPS,
+			Host:   "static.adtidy.org",
+			Path:   path.Join("adguardhome", version.Channel(), "version.json"),
+		}
+	}
+
+	log.Debug("using config path %q for updater", confPath)
+
+	return updater.NewUpdater(&updater.Config{
+		Client:          config.Filtering.HTTPClient,
+		Version:         version.Version(),
+		Channel:         version.Channel(),
+		GOARCH:          runtime.GOARCH,
+		GOOS:            runtime.GOOS,
+		GOARM:           version.GOARM(),
+		GOMIPS:          version.GOMIPS(),
+		WorkDir:         workDir,
+		ConfName:        confPath,
+		ExecPath:        execPath,
+		VersionCheckURL: versionURL,
+	})
+}
+
 // initUsers initializes context auth module.  Clears config users field.
 func initUsers() (auth *Auth, err error) {
 	sessFilename := filepath.Join(Context.getDataDir(), "sessions.db")
@@ -1018,8 +1040,7 @@ func cmdlineUpdate(opts options, upd *updater.Updater, l *slog.Logger) {
 
 	info, err := upd.VersionInfo(true)
 	if err != nil {
-		vcu := upd.VersionCheckURL()
-		log.Error("getting version info from %s: %s", vcu, err)
+		log.Error("getting version info: %s", err)
 
 		os.Exit(1)
 	}
diff --git a/internal/updater/check.go b/internal/updater/check.go
index 84da6281..2a3e2cfe 100644
--- a/internal/updater/check.go
+++ b/internal/updater/check.go
@@ -13,6 +13,7 @@ import (
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/ioutil"
 	"github.com/AdguardTeam/golibs/log"
+	"github.com/c2h5oh/datasize"
 )
 
 // TODO(a.garipov): Make configurable.
@@ -28,8 +29,9 @@ type VersionInfo struct {
 	CanAutoUpdate aghalg.NullBool `json:"can_autoupdate,omitempty"`
 }
 
-// MaxResponseSize is responses on server's requests maximum length in bytes.
-const MaxResponseSize = 64 * 1024
+// maxVersionRespSize is the maximum length in bytes for version information
+// response.
+const maxVersionRespSize datasize.ByteSize = 64 * datasize.KB
 
 // VersionInfo downloads the latest version information.  If forceRecheck is
 // false and there are cached results, those results are returned.
@@ -51,7 +53,7 @@ func (u *Updater) VersionInfo(forceRecheck bool) (vi VersionInfo, err error) {
 	}
 	defer func() { err = errors.WithDeferred(err, resp.Body.Close()) }()
 
-	r := ioutil.LimitReader(resp.Body, MaxResponseSize)
+	r := ioutil.LimitReader(resp.Body, maxVersionRespSize.Bytes())
 
 	// This use of ReadAll is safe, because we just limited the appropriate
 	// ReadCloser.
diff --git a/internal/updater/check_test.go b/internal/updater/check_test.go
index e61ba443..5a7c0f5d 100644
--- a/internal/updater/check_test.go
+++ b/internal/updater/check_test.go
@@ -51,9 +51,11 @@ func TestUpdater_VersionInfo(t *testing.T) {
 	}))
 	t.Cleanup(srv.Close)
 
-	fakeURL, err := url.JoinPath(srv.URL, "adguardhome", version.ChannelBeta, "version.json")
+	srvURL, err := url.Parse(srv.URL)
 	require.NoError(t, err)
 
+	fakeURL := srvURL.JoinPath("adguardhome", version.ChannelBeta, "version.json")
+
 	u := updater.NewUpdater(&updater.Config{
 		Client:          srv.Client(),
 		Version:         "v0.103.0-beta.1",
@@ -134,7 +136,7 @@ func TestUpdater_VersionInfo_others(t *testing.T) {
 			GOARCH:          tc.arch,
 			GOARM:           tc.arm,
 			GOMIPS:          tc.mips,
-			VersionCheckURL: fakeURL.String(),
+			VersionCheckURL: fakeURL,
 		})
 
 		info, err := u.VersionInfo(false)
diff --git a/internal/updater/updater.go b/internal/updater/updater.go
index 85cb69b0..704ba990 100644
--- a/internal/updater/updater.go
+++ b/internal/updater/updater.go
@@ -9,6 +9,7 @@ import (
 	"io"
 	"io/fs"
 	"net/http"
+	"net/url"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -65,6 +66,9 @@ type Updater struct {
 type Config struct {
 	Client *http.Client
 
+	// VersionCheckURL is url to the latest version announcement.
+	VersionCheckURL *url.URL
+
 	Version string
 	Channel string
 	GOARCH  string
@@ -81,9 +85,6 @@ type Config struct {
 
 	// ExecPath is path to the executable file.
 	ExecPath string
-
-	// VersionCheckURL is url to the latest version announcement.
-	VersionCheckURL string
 }
 
 // NewUpdater creates a new Updater.
@@ -101,7 +102,7 @@ func NewUpdater(conf *Config) *Updater {
 		confName:        conf.ConfName,
 		workDir:         conf.WorkDir,
 		execPath:        conf.ExecPath,
-		versionCheckURL: conf.VersionCheckURL,
+		versionCheckURL: conf.VersionCheckURL.String(),
 
 		mu: &sync.RWMutex{},
 	}
@@ -167,14 +168,6 @@ func (u *Updater) NewVersion() (nv string) {
 	return u.newVersion
 }
 
-// VersionCheckURL returns the version check URL.
-func (u *Updater) VersionCheckURL() (vcu string) {
-	u.mu.RLock()
-	defer u.mu.RUnlock()
-
-	return u.versionCheckURL
-}
-
 // prepare fills all necessary fields in Updater object.
 func (u *Updater) prepare() (err error) {
 	u.updateDir = filepath.Join(u.workDir, fmt.Sprintf("agh-update-%s", u.newVersion))
diff --git a/internal/updater/updater_internal_test.go b/internal/updater/updater_internal_test.go
index e233db3d..0ed94641 100644
--- a/internal/updater/updater_internal_test.go
+++ b/internal/updater/updater_internal_test.go
@@ -1,6 +1,7 @@
 package updater
 
 import (
+	"net/url"
 	"os"
 	"path/filepath"
 	"testing"
@@ -59,6 +60,9 @@ func TestUpdater_internal(t *testing.T) {
 			ExecPath: exePath,
 			WorkDir:  wd,
 			ConfName: yamlPath,
+			// TODO(e.burkov):  Rewrite the test to use a fake version check
+			// URL with a fake URLs for the package files.
+			VersionCheckURL: &url.URL{},
 		})
 
 		u.newVersion = "v0.103.1"
@@ -72,36 +76,40 @@ func TestUpdater_internal(t *testing.T) {
 
 		u.clean()
 
-		// check backup files
-		d, err := os.ReadFile(filepath.Join(wd, "agh-backup", "AdGuardHome.yaml"))
-		require.NoError(t, err)
+		t.Run("backup", func(t *testing.T) {
+			var d []byte
+			d, err = os.ReadFile(filepath.Join(wd, "agh-backup", "AdGuardHome.yaml"))
+			require.NoError(t, err)
 
-		assert.Equal(t, "AdGuardHome.yaml", string(d))
+			assert.Equal(t, "AdGuardHome.yaml", string(d))
 
-		d, err = os.ReadFile(filepath.Join(wd, "agh-backup", tc.exeName))
-		require.NoError(t, err)
+			d, err = os.ReadFile(filepath.Join(wd, "agh-backup", tc.exeName))
+			require.NoError(t, err)
 
-		assert.Equal(t, tc.exeName, string(d))
+			assert.Equal(t, tc.exeName, string(d))
+		})
 
-		// check updated files
-		d, err = os.ReadFile(exePath)
-		require.NoError(t, err)
+		t.Run("updated", func(t *testing.T) {
+			var d []byte
+			d, err = os.ReadFile(exePath)
+			require.NoError(t, err)
 
-		assert.Equal(t, "1", string(d))
+			assert.Equal(t, "1", string(d))
 
-		d, err = os.ReadFile(readmePath)
-		require.NoError(t, err)
+			d, err = os.ReadFile(readmePath)
+			require.NoError(t, err)
 
-		assert.Equal(t, "2", string(d))
+			assert.Equal(t, "2", string(d))
 
-		d, err = os.ReadFile(licensePath)
-		require.NoError(t, err)
+			d, err = os.ReadFile(licensePath)
+			require.NoError(t, err)
 
-		assert.Equal(t, "3", string(d))
+			assert.Equal(t, "3", string(d))
 
-		d, err = os.ReadFile(yamlPath)
-		require.NoError(t, err)
+			d, err = os.ReadFile(yamlPath)
+			require.NoError(t, err)
 
-		assert.Equal(t, "AdGuardHome.yaml", string(d))
+			assert.Equal(t, "AdGuardHome.yaml", string(d))
+		})
 	}
 }
diff --git a/internal/updater/updater_test.go b/internal/updater/updater_test.go
index 4af567c0..735d9c99 100644
--- a/internal/updater/updater_test.go
+++ b/internal/updater/updater_test.go
@@ -65,7 +65,10 @@ func TestUpdater_Update(t *testing.T) {
 	srv := httptest.NewServer(mux)
 	t.Cleanup(srv.Close)
 
-	versionCheckURL, err := url.JoinPath(srv.URL, versionPath)
+	srvURL, err := url.Parse(srv.URL)
+	require.NoError(t, err)
+
+	versionCheckURL := srvURL.JoinPath(versionPath)
 	require.NoError(t, err)
 
 	u := updater.NewUpdater(&updater.Config{