diff --git a/flutter/lib/common/formatter/id_formatter.dart b/flutter/lib/common/formatter/id_formatter.dart
index c2329d53f..79c4bc6b1 100644
--- a/flutter/lib/common/formatter/id_formatter.dart
+++ b/flutter/lib/common/formatter/id_formatter.dart
@@ -33,8 +33,13 @@ class IDTextInputFormatter extends TextInputFormatter {
   }
 }
 
+// Pasted IDs can carry a trailing newline or tab (e.g. copied from a
+// spreadsheet cell) or non-breaking spaces, so strip all whitespace, not only
+// plain spaces.
+final _whitespace = RegExp(r'\s');
+
 String formatID(String id) {
-  String id2 = id.replaceAll(' ', '');
+  String id2 = id.replaceAll(_whitespace, '');
   String suffix = '';
   if (id2.endsWith(r'\r') || id2.endsWith(r'/r')) {
     suffix = id2.substring(id2.length - 2, id2.length);
@@ -56,5 +61,5 @@ String formatID(String id) {
 }
 
 String trimID(String id) {
-  return id.replaceAll(' ', '');
+  return id.replaceAll(_whitespace, '');
 }
diff --git a/flutter/test/id_formatter_test.dart b/flutter/test/id_formatter_test.dart
new file mode 100644
index 000000000..b1a271ec4
--- /dev/null
+++ b/flutter/test/id_formatter_test.dart
@@ -0,0 +1,44 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_hbb/common/formatter/id_formatter.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('formatID', () {
+    test('groups typed IDs from the right', () {
+      expect(formatID('53464938'), '53 464 938');
+      expect(formatID('123456789'), '123 456 789');
+      expect(formatID('1234'), '1 234');
+    });
+
+    test('ignores line breaks, tabs and non-breaking spaces from a paste', () {
+      expect(formatID('53464938\r\n'), '53 464 938');
+      expect(formatID('53464938\n'), '53 464 938');
+      expect(formatID('\t53464938'), '53 464 938');
+      expect(formatID('53\u00a0464\u00a0938'), '53 464 938');
+    });
+
+    test('keeps the relay suffix', () {
+      expect(formatID(r'53464938\r'), r'53 464 938\r');
+    });
+
+    test('leaves non-numeric input alone', () {
+      expect(formatID('my-host.example.com'), 'my-host.example.com');
+    });
+  });
+
+  test('trimID drops all whitespace', () {
+    expect(trimID('53 464 938\r\n'), '53464938');
+    expect(trimID('53\u00a0464\u00a0938'), '53464938');
+  });
+
+  test('pasting an ID with a trailing newline formats it like typing', () {
+    final formatted = IDTextInputFormatter().formatEditUpdate(
+      TextEditingValue.empty,
+      const TextEditingValue(
+        text: '53464938\r\n',
+        selection: TextSelection.collapsed(offset: 10),
+      ),
+    );
+    expect(formatted.text, '53 464 938');
+  });
+}