diff --git a/TODO.md b/TODO.md
index 3570099..3c4703d 100644
--- a/TODO.md
+++ b/TODO.md
@@ -20,6 +20,13 @@ regress.
 
 # Completed Steps
 
+- 2026-10-02: App names may contain dots, such as `sneak.berlin`: lowercase
+  letters and numbers joined by single dots or by hyphens, 2 to 63 characters.
+  Docker accepts every such name in the image name `upaas-<name>`; a dot needs a
+  letter or number on both sides because Docker requires it. The new and edit
+  app forms check the same rule; browsers ignored their old pattern, which was
+  not a valid regular expression there (#260).
+
 - 2026-10-02: `.dockerignore` leaves out `.git/config`, so a remote URL there
   that carries a credential no longer goes into the Docker build; the image
   still shows the commit it was built from (#269).
diff --git a/go.mod b/go.mod
index c85cc4d..b2de996 100644
--- a/go.mod
+++ b/go.mod
@@ -4,6 +4,7 @@ go 1.25
 
 require (
 	github.com/99designs/basicauth-go v0.0.0-20230316000542-bf6f9cbbf0f8
+	github.com/distribution/reference v0.6.0
 	github.com/docker/docker v27.3.1+incompatible
 	github.com/docker/go-connections v0.6.0
 	github.com/go-chi/chi/v5 v5.2.3
@@ -39,7 +40,6 @@ require (
 	github.com/containerd/ttrpc v1.2.5 // indirect
 	github.com/containerd/typeurl/v2 v2.2.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/distribution/reference v0.6.0 // indirect
 	github.com/docker/go-units v0.5.0 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
diff --git a/internal/handlers/app_name_validation.go b/internal/handlers/app_name_validation.go
index d1d1abb..f6bf1e9 100644
--- a/internal/handlers/app_name_validation.go
+++ b/internal/handlers/app_name_validation.go
@@ -13,12 +13,15 @@ const (
 	appNameMaxLength = 63
 )
 
-// validAppNameRe matches names containing only lowercase alphanumeric characters and
-// hyphens, starting and ending with an alphanumeric character.
-var validAppNameRe = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*[a-z0-9]$`)
+// validAppNameRe matches runs of lowercase letters and digits joined by
+// single dots or by hyphens, such as "my-app" or "sneak.berlin". Docker
+// accepts every name it allows as the app's image name, upaas-<name>; a
+// dot needs a letter or digit on both sides because Docker requires it.
+// It also keeps the name from being "." or ".." or starting or ending
+// with a dot, so it is safe as a directory and file name. The pattern
+// attribute of the name field on the new and edit app forms is the same.
+var validAppNameRe = regexp.MustCompile(`^[a-z0-9]+((\.|-+)[a-z0-9]+)*$`)
 
-// validateAppName checks that the given app name is safe for use in Docker
-// container names, image tags, and file system paths.
 var (
 	errAppNameLength = errors.New(
 		"app name must be between " +
@@ -26,11 +29,14 @@ var (
 			strconv.Itoa(appNameMaxLength) + " characters",
 	)
 	errAppNamePattern = errors.New(
-		"app name must contain only lowercase letters, numbers, " +
-			"and hyphens, and must start and end with a letter or number",
+		"app name must contain only lowercase letters, numbers, hyphens, " +
+			"and dots, must start and end with a letter or number, " +
+			"and must have a letter or number on both sides of each dot",
 	)
 )
 
+// validateAppName checks that the given app name is safe for use in Docker
+// container names, image tags, and file system paths.
 func validateAppName(name string) error {
 	if len(name) < appNameMinLength || len(name) > appNameMaxLength {
 		return errAppNameLength
diff --git a/internal/handlers/app_name_validation_test.go b/internal/handlers/app_name_validation_test.go
index b4120fb..f5e13a3 100644
--- a/internal/handlers/app_name_validation_test.go
+++ b/internal/handlers/app_name_validation_test.go
@@ -1,7 +1,16 @@
 package handlers //nolint:testpackage // testing unexported validateAppName
 
 import (
+	"bytes"
+	"strconv"
+	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/templates"
 )
 
 func TestValidateAppName(t *testing.T) {
@@ -18,6 +27,10 @@ func TestValidateAppName(t *testing.T) {
 		{"valid two chars", "ab", false},
 		{"valid complex", "my-cool-app-v2", false},
 		{"valid all numbers", "123", false},
+		{"valid double hyphen", "my--app", false},
+		{"valid domain", "sneak.berlin", false},
+		{"valid two dots", "www.sneak.berlin", false},
+		{"valid dot and hyphen", "my-app.example.com", false},
 		{"empty", "", true},
 		{"single char", "a", true},
 		{"too long", "a" + string(make([]byte, 63)), true},
@@ -36,7 +49,12 @@ func TestValidateAppName(t *testing.T) {
 		{"starts with hyphen", "-myapp", true},
 		{"ends with hyphen", "myapp-", true},
 		{"underscore", "my_app", true},
-		{"dot", "my.app", true},
+		{"two dots in a row", "a..b", true},
+		{"starts with dot", ".a", true},
+		{"ends with dot", "a.", true},
+		{"only dots", "..", true},
+		{"hyphen before dot", "a-.b", true},
+		{"hyphen after dot", "a.-b", true},
 		{"slash", "my/app", true},
 		{"path traversal", "../etc/passwd", true},
 		{"special chars", "app@name!", true},
@@ -54,3 +72,42 @@ func TestValidateAppName(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateAppNameErrorMentionsDots(t *testing.T) {
+	t.Parallel()
+
+	err := validateAppName("a..b")
+
+	require.ErrorIs(t, err, errAppNamePattern)
+	assert.Contains(t, err.Error(), "dots")
+}
+
+// TestAppFormsCheckAppNameLikeServer checks that the name field on the new
+// and edit app forms has the server's pattern and length limits, and that
+// its hint mentions dots.
+func TestAppFormsCheckAppNameLikeServer(t *testing.T) {
+	t.Parallel()
+
+	pattern := strings.TrimSuffix(strings.TrimPrefix(validAppNameRe.String(), "^"), "$")
+
+	pages := map[string]map[string]any{
+		"app_new.html":  {},
+		"app_edit.html": {dataKeyApp: &models.App{}},
+	}
+
+	for page, data := range pages {
+		var out bytes.Buffer
+
+		require.NoError(t, templates.GetParsed().ExecuteTemplate(&out, page, data))
+
+		// The name field and its hint, up to the end of their div.
+		_, field, found := strings.Cut(out.String(), `id="name"`)
+		require.True(t, found, page)
+
+		field, _, _ = strings.Cut(field, "</div>")
+		assert.Contains(t, field, `pattern="`+pattern+`"`, page)
+		assert.Contains(t, field, `minlength="`+strconv.Itoa(appNameMinLength)+`"`, page)
+		assert.Contains(t, field, `maxlength="`+strconv.Itoa(appNameMaxLength)+`"`, page)
+		assert.Contains(t, field, "hyphens, and dots", page)
+	}
+}
diff --git a/internal/service/deploy/deploy_app_name_test.go b/internal/service/deploy/deploy_app_name_test.go
new file mode 100644
index 0000000..3890c95
--- /dev/null
+++ b/internal/service/deploy/deploy_app_name_test.go
@@ -0,0 +1,121 @@
+package deploy_test
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"slices"
+	"strings"
+	"testing"
+
+	"github.com/distribution/reference"
+	"github.com/docker/docker/daemon/names"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/database"
+	"sneak.berlin/go/upaas/internal/globals"
+	"sneak.berlin/go/upaas/internal/handlers"
+	"sneak.berlin/go/upaas/internal/logger"
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/internal/service/app"
+)
+
+// TestDeployAppWithDotInName creates an app named sneak.berlin through the
+// new app form, as a user does, then builds and deploys it against a fake
+// Docker API and checks that Docker accepts the names of the image it
+// builds and of the container it runs, using Docker's own rules for each.
+func TestDeployAppWithDotInName(t *testing.T) {
+	t.Parallel()
+
+	api := &fakeImageAPI{
+		images:   map[string][]string{},
+		shortSHA: "abc1234",
+		nextID:   "sha256:built",
+	}
+	svc, db := newImageTestService(t, api)
+	ctx := context.Background()
+
+	createdApp := createAppWithForm(t, db, "sneak.berlin")
+
+	deployment := models.NewDeployment(db)
+	deployment.AppID = createdApp.ID
+	require.NoError(t, deployment.Save(ctx))
+
+	imageID, err := svc.BuildImage(ctx, createdApp, deployment)
+	require.NoError(t, err)
+	require.NoError(t, svc.DeployContainer(ctx, createdApp, deployment, imageID))
+
+	images, _ := api.state()
+
+	api.mu.Lock()
+	containers := slices.Clone(api.containers)
+	api.mu.Unlock()
+
+	require.Equal(t, map[string][]string{
+		"sha256:built": {"upaas-sneak.berlin:abc1234"},
+	}, images)
+
+	_, err = reference.ParseNormalizedNamed("upaas-sneak.berlin:abc1234")
+	require.NoError(t, err)
+
+	require.Equal(t, []string{"upaas-sneak.berlin"}, containers)
+	assert.Regexp(t, names.RestrictedNamePattern, containers[0])
+
+	assert.DirExists(t, svc.GetBuildDirExported(createdApp.Name))
+}
+
+// createAppWithForm posts the new app form with the given name, which
+// checks the name as it does for a user, and returns the app it created.
+func createAppWithForm(
+	t *testing.T,
+	db *database.Database,
+	name string,
+) *models.App {
+	t.Helper()
+
+	log := logger.NewForTest(slog.New(slog.NewTextHandler(os.Stderr, nil)))
+
+	appSvc, err := app.New(nil, app.ServiceParams{Logger: log, Database: db})
+	require.NoError(t, err)
+
+	globalInstance, err := globals.New(nil)
+	require.NoError(t, err)
+
+	handlersInstance, err := handlers.New(nil, handlers.Params{
+		Logger:   log,
+		Globals:  globalInstance,
+		Database: db,
+		App:      appSvc,
+	})
+	require.NoError(t, err)
+
+	form := url.Values{
+		"name":     {name},
+		"repo_url": {"git@example.com:sneak/" + name + ".git"},
+	}
+	request := httptest.NewRequestWithContext(
+		t.Context(), http.MethodPost, "/apps", strings.NewReader(form.Encode()),
+	)
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	recorder := httptest.NewRecorder()
+
+	handlersInstance.HandleAppCreate().ServeHTTP(recorder, request)
+
+	// The form redirects to the new app's page; it shows the form again,
+	// with the error, when it refuses the name.
+	require.Equal(t, http.StatusSeeOther, recorder.Code, recorder.Body.String())
+
+	appID, found := strings.CutPrefix(recorder.Header().Get("Location"), "/apps/")
+	require.True(t, found)
+
+	createdApp, err := models.FindApp(t.Context(), db, appID)
+	require.NoError(t, err)
+	require.NotNil(t, createdApp)
+
+	return createdApp
+}
diff --git a/internal/service/deploy/deploy_images_test.go b/internal/service/deploy/deploy_images_test.go
index 7e93849..7141c25 100644
--- a/internal/service/deploy/deploy_images_test.go
+++ b/internal/service/deploy/deploy_images_test.go
@@ -35,12 +35,13 @@ import (
 // an image's last tag, or an untagged image by its ID, deletes the image.
 // It also answers the steps of a git clone that reports shortSHA.
 type fakeImageAPI struct {
-	mu       sync.Mutex
-	images   map[string][]string // image ID -> tags
-	shortSHA string              // the commit's short hash the clone reports
-	nextID   string              // ID of the image the next build creates
-	removed  []string            // each tag or ID removed
-	forced   bool                // whether a removal was forced
+	mu         sync.Mutex
+	images     map[string][]string // image ID -> tags
+	shortSHA   string              // the commit's short hash the clone reports
+	nextID     string              // ID of the image the next build creates
+	removed    []string            // each tag or ID removed
+	forced     bool                // whether a removal was forced
+	containers []string            // name of each named container created
 }
 
 func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -67,6 +68,11 @@ func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case strings.HasSuffix(r.URL.Path, "/version"):
 		_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
 	case strings.HasSuffix(r.URL.Path, "/containers/create"):
+		// The git clone's container has no name; the app's has.
+		if containerName := r.URL.Query().Get("name"); containerName != "" {
+			api.containers = append(api.containers, containerName)
+		}
+
 		_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
 	case strings.HasSuffix(r.URL.Path, "/logs"):
 		writeCloneOutput(w, api.shortSHA)
diff --git a/internal/service/deploy/export_test.go b/internal/service/deploy/export_test.go
index 8abfc34..0ea6119 100644
--- a/internal/service/deploy/export_test.go
+++ b/internal/service/deploy/export_test.go
@@ -113,6 +113,16 @@ func (svc *Service) BuildImage(
 	return svc.buildImage(ctx, app, deployment)
 }
 
+// DeployContainer exposes deployContainerWithTimeout for testing.
+func (svc *Service) DeployContainer(
+	ctx context.Context,
+	app *models.App,
+	deployment *models.Deployment,
+	imageID docker.ImageID,
+) error {
+	return svc.deployContainerWithTimeout(ctx, app, deployment, imageID)
+}
+
 // BuildContainerOptionsExported exposes buildContainerOptions for testing.
 func (svc *Service) BuildContainerOptionsExported(
 	ctx context.Context,
diff --git a/templates/app_edit.html b/templates/app_edit.html
index 3bb3852..eece07f 100644
--- a/templates/app_edit.html
+++ b/templates/app_edit.html
@@ -30,10 +30,12 @@
                     name="name"
                     value="{{.App.Name}}"
                     required
-                    pattern="[a-z0-9-]+"
+                    minlength="2"
+                    maxlength="63"
+                    pattern="[a-z0-9]+((\.|-+)[a-z0-9]+)*"
                     class="input"
                 >
-                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, and hyphens only</p>
+                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, hyphens, and dots, such as my-app or example.com</p>
             </div>
 
             <div class="form-group">
diff --git a/templates/app_new.html b/templates/app_new.html
index 101fc6a..8a32a92 100644
--- a/templates/app_new.html
+++ b/templates/app_new.html
@@ -30,11 +30,13 @@
                     name="name"
                     value="{{.Name}}"
                     required
-                    pattern="[a-z0-9-]+"
+                    minlength="2"
+                    maxlength="63"
+                    pattern="[a-z0-9]+((\.|-+)[a-z0-9]+)*"
                     class="input"
                     placeholder="my-app"
                 >
-                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, and hyphens only</p>
+                <p class="text-sm text-gray-500 mt-1">Lowercase letters, numbers, hyphens, and dots, such as my-app or example.com</p>
             </div>
 
             <div class="form-group">