diff --git a/lib/src/logic/zxing.dart b/lib/src/logic/zxing.dart
index e4c22e4..9e96ffb 100644
--- a/lib/src/logic/zxing.dart
+++ b/lib/src/logic/zxing.dart
@@ -29,7 +29,7 @@ void setZxingLogEnabled(bool enabled) =>
     bindings.setLogEnabled(enabled ? 1 : 0);
 
 /// Returns a readable barcode format name
-String zxingBarcodeFormatName(int format) => formatNames[format] ?? 'Unknown';
+String zxingBarcodeFormatName(int format) => barcodeNames[format] ?? 'Unknown';
 
 extension Uint8ListBlobConversion on Uint8List {
   /// Allocates a pointer filled with the Uint8List data.
diff --git a/lib/src/models/format.dart b/lib/src/models/format.dart
index 6d3fda9..ee948ab 100644
--- a/lib/src/models/format.dart
+++ b/lib/src/models/format.dart
@@ -35,22 +35,24 @@ abstract class Format {
   static const int any = oneDCodes | twoDCodes;
 }
 
-extension EccSupportedExtension on int {
+extension CodeFormat on int {
+  String get name => barcodeNames[this] ?? 'Unknown';
+
+  // The width divided by the height of the barcode
+  double get ratio => barcodeRatios[this] ?? 1.0;
+  String get demoText => barcodeDemoText[this] ?? '';
+  int get maxTextLength => barcodeMaxTextLengths[this] ?? 0;
   bool get isSupportedEccLevel => eccSupported.contains(this);
 
   static final List<int> eccSupported = <int>[
     Format.qrCode,
   ];
-}
-
-extension CodeFormat on Format {
-  String get name => formatNames[this] ?? 'Unknown';
 
-  static final List<int> writerFormats = <int>[
+  static final List<int> supportedEncodeFormats = <int>[
     Format.qrCode,
     Format.dataMatrix,
     Format.aztec,
-    Format.pdf417,
+    // Format.pdf417,
     Format.codabar,
     Format.code39,
     Format.code93,
@@ -66,7 +68,7 @@ extension CodeFormat on Format {
   ];
 }
 
-final Map<int, String> formatNames = <int, String>{
+final Map<int, String> barcodeNames = <int, String>{
   Format.none: 'None',
   Format.aztec: 'Aztec',
   Format.codabar: 'CodaBar',
@@ -88,3 +90,60 @@ final Map<int, String> formatNames = <int, String>{
   Format.twoDCodes: 'TwoD',
   Format.any: 'Any',
 };
+
+final Map<int, double> barcodeRatios = <int, double>{
+  Format.aztec: 3.0 / 3.0, // recommended ratio: 3:3 (square)
+  Format.codabar: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.code39: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.code93: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.code128: 2.0 / 1.0, // recommended ratio: 2:1
+  Format.dataBar: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.dataBarExpanded: 1.0 / 1.0, // recommended ratio: 1:1 (square)
+  Format.dataMatrix: 3.0 / 3.0, // recommended ratio: 3:3 (square)
+  Format.ean8: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.ean13: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.itf: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.maxiCode: 3.0 / 3.0, // recommended ratio: 3:3 (square)
+  Format.pdf417: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.qrCode: 3.0 / 3.0, // recommended ratio: 3:3 (square)
+  Format.upca: 3.0 / 1.0, // recommended ratio: 3:1
+  Format.upce: 1.0 / 1.0, // recommended ratio: 1:1 (square)
+};
+
+final Map<int, String> barcodeDemoText = <int, String>{
+  Format.aztec: 'This is an Aztec Code',
+  Format.codabar: 'A123456789B',
+  Format.code39: 'ABC-1234',
+  Format.code93: 'ABC-1234-/+',
+  Format.code128: 'ABC-abc-1234',
+  Format.dataBar: '0123456789012',
+  Format.dataBarExpanded: '011234567890123-ABCabc',
+  Format.dataMatrix: 'This is a Data Matrix',
+  Format.ean8: '9031101',
+  Format.ean13: '978020137962',
+  Format.itf: '00012345600012',
+  Format.maxiCode: 'This is a MaxiCode',
+  Format.pdf417: 'This is a PDF417',
+  Format.qrCode: 'This is a QR Code',
+  Format.upca: '72527273070',
+  Format.upce: '0123456',
+};
+
+final Map<int, int> barcodeMaxTextLengths = <int, int>{
+  Format.aztec: 3832,
+  Format.codabar: 20,
+  Format.code39: 43,
+  Format.code93: 47,
+  Format.code128: 2046,
+  Format.dataBar: 74,
+  Format.dataBarExpanded: 4107,
+  Format.dataMatrix: 2335,
+  Format.ean8: 8,
+  Format.ean13: 13,
+  Format.itf: 20,
+  Format.maxiCode: 30,
+  Format.pdf417: 2953,
+  Format.qrCode: 4296,
+  Format.upca: 12,
+  Format.upce: 8,
+};
diff --git a/lib/src/ui/writer_widget.dart b/lib/src/ui/writer_widget.dart
index e57dcff..11e3903 100644
--- a/lib/src/ui/writer_widget.dart
+++ b/lib/src/ui/writer_widget.dart
@@ -9,10 +9,9 @@ import '../../flutter_zxing.dart';
 class WriterWidget extends StatefulWidget {
   const WriterWidget({
     super.key,
-    this.text = '',
+    this.text,
     this.format = Format.qrCode,
-    this.width = 120,
-    this.height = 120,
+    this.height = 120, // Width is calculated from height and format ratio
     this.margin = 0,
     this.eccLevel = EccLevel.low,
     this.messages = const Messages(),
@@ -20,9 +19,8 @@ class WriterWidget extends StatefulWidget {
     this.onError,
   });
 
-  final String text;
+  final String? text;
   final int format;
-  final int width;
   final int height;
   final int margin;
   final EccLevel eccLevel;
@@ -44,8 +42,7 @@ class _WriterWidgetState extends State<WriterWidget>
 
   bool isAndroid() => Theme.of(context).platform == TargetPlatform.android;
 
-  final int _maxTextLength = 2000;
-  final List<int> _supportedFormats = CodeFormat.writerFormats;
+  final List<int> _supportedFormats = CodeFormat.supportedEncodeFormats;
 
   int _codeFormat = Format.qrCode;
   EccLevel _eccLevel = EccLevel.low;
@@ -60,12 +57,13 @@ class _WriterWidgetState extends State<WriterWidget>
 
   @override
   void initState() {
-    _textController.text = widget.text;
-    _widthController.text = widget.width.toString();
+    _codeFormat = widget.format;
+    _eccLevel = widget.eccLevel;
+    _textController.text = widget.text ?? _codeFormat.demoText;
+    _widthController.text =
+        (widget.height * _codeFormat.ratio).round().toString();
     _heightController.text = widget.height.toString();
     _marginController.text = widget.margin.toString();
-    _eccLevel = widget.eccLevel;
-    _codeFormat = widget.format;
     super.initState();
   }
 
@@ -95,7 +93,7 @@ class _WriterWidgetState extends State<WriterWidget>
                 controller: _textController,
                 keyboardType: TextInputType.multiline,
                 maxLines: null,
-                maxLength: _maxTextLength,
+                maxLength: _codeFormat.maxTextLength,
                 onChanged: (String value) {
                   setState(() {});
                 },
@@ -104,7 +102,7 @@ class _WriterWidgetState extends State<WriterWidget>
                   filled: true,
                   labelText: messages.textLabel,
                   counterText:
-                      '${_textController.value.text.length} / $_maxTextLength',
+                      '${_textController.value.text.length} / ${_codeFormat.maxTextLength}',
                 ),
                 validator: (String? value) {
                   if (value?.isEmpty ?? false) {
@@ -134,6 +132,12 @@ class _WriterWidgetState extends State<WriterWidget>
                       onChanged: (int? format) {
                         setState(() {
                           _codeFormat = format ?? Format.qrCode;
+                          _textController.text = _codeFormat.demoText;
+                          _heightController.text = widget.height.toString();
+                          _widthController.text =
+                              (widget.height * _codeFormat.ratio)
+                                  .round()
+                                  .toString();
                         });
                       },
                     ),
@@ -182,6 +186,15 @@ class _WriterWidgetState extends State<WriterWidget>
                         }
                         return null;
                       },
+                      onChanged: (String value) {
+                        // use format ratio to calculate height
+                        final int? width = int.tryParse(value);
+                        if (width != null) {
+                          final int height =
+                              (width / _codeFormat.ratio).round();
+                          _heightController.text = height.toString();
+                        }
+                      },
                     ),
                   ),
                   // const SizedBox(width: 8),
@@ -199,6 +212,15 @@ class _WriterWidgetState extends State<WriterWidget>
                         }
                         return null;
                       },
+                      onChanged: (String value) {
+                        // use format ratio to calculate width
+                        final int? height = int.tryParse(value);
+                        if (height != null) {
+                          final int width =
+                              (height * _codeFormat.ratio).round();
+                          _widthController.text = width.toString();
+                        }
+                      },
                     ),
                   ),
                   Flexible(
@@ -219,7 +241,6 @@ class _WriterWidgetState extends State<WriterWidget>
                   ),
                 ],
               ),
-
               const SizedBox(height: 20),
               // Write button
               ElevatedButton(