diff --git a/.travis.yml b/.travis.yml
index 907c25a..f34980d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -40,7 +40,9 @@ jobs:
           branch: master
 
 branches:
-  only: [master, develop]
+  only: 
+    - master
+    - /^v\d+\.\d+\.\d+.*$/
 
 # Incremental pub cache and builds.
 cache:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 72e7fe2..e9278bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.4.0 (Null Safety)
+
+* thanx for migrating to null safety to [@timekone](https://github.com/timekone) and this [PR](https://github.com/NiKoTron/dart-tags/pull/35)
+* updated some dependencies
+
 ## 0.3.1
 
 * implemented separate getting size of frame for id3 v2.3 and v2.4
diff --git a/README.md b/README.md
index 4e7fad5..2c6ab6f 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,11 @@ project under MIT [license](LICENSE)
 
 [full changelog](CHANGELOG.md)
 
+## 0.4.0 (Null Safety)
+
+* thanx for migrating to null safety to [@timekone](https://github.com/timekone) and this [PR](https://github.com/NiKoTron/dart-tags/pull/35)
+* updated some dependencies
+
 ## 0.3.1
 
 * implemented separate getting size of frame for id3 v2.3 and v2.4
@@ -24,21 +29,6 @@ project under MIT [license](LICENSE)
 * fixed typos, thanx to [@algoshipda](https://github.com/algoshipda) and his [PR](https://github.com/NiKoTron/dart-tags/pull/17)
 * fixed APIC picture type error, thanx to [@algoshipda](https://github.com/algoshipda) and his [PR](https://github.com/NiKoTron/dart-tags/pull/20)
 
-## 0.3.0+1
-
-* hotfix! missed exports for new tags was added
-
-## 0.3.0 (BREAKING CHANGES)
-
-* COMM, APIC, USLT, WXXX tags returns as a map
-* WXXX frame returns WURL object
-* various fixes
-* added USLT tag
-* added possibility to pass many COMM, APIC, USLT tags
-* APIC processing was refactored
-* hex encoder
-* unrecognized encoding falls to hex encoder (removed unsupported encoding error)
-* unsupported tags like PRIV will be printed just like raw binary data
 
 ## Instalation
 
@@ -46,7 +36,7 @@ add dependency in pubsec.yaml
 
 ``` yaml
 dependencies:
-  dart_tags: ^0.3.1
+  dart_tags: ^0.4.0
 ```
 
 ## Usage
@@ -59,9 +49,9 @@ import 'dart:io';
 import 'package:dart_tags/dart_tags.dart';
 
 main(List<String> args) {
-  TagProcessor tp = new TagProcessor();
+  final tp = new TagProcessor();
 
-  File f = new File(args[0]);
+  final f = new File(args[0]);
 
   tp.getTagsFromByteArray(f.readAsBytes()).then((l) => l.forEach((f) => print(f)));
 }
diff --git a/analysis_options.yaml b/analysis_options.yaml
index 36bdda4..8cb0247 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -1,5 +1,4 @@
-# Lint rules that uses google internaly also in pu i guess. https://github.com/dart-lang/pedantic/#enabled-lints
-include: package:pedantic/analysis_options.yaml
+include: package:lints/recommended.yaml
 
 analyzer:
   strong-mode:
@@ -48,7 +47,6 @@ linter:
     - always_put_required_named_parameters_first
     - always_require_non_null_named_parameters
     - annotate_overrides
-    - avoid_as
     - avoid_annotating_with_dynamic
     - avoid_classes_with_only_static_members
     - avoid_bool_literals_in_conditional_expressions
@@ -68,4 +66,3 @@ linter:
     - prefer_single_quotes
     - package_api_docs
 #    - public_member_api_docs
-    
\ No newline at end of file
diff --git a/lib/src/convert/utf16.dart b/lib/src/convert/utf16.dart
index b63e518..4f913e3 100644
--- a/lib/src/convert/utf16.dart
+++ b/lib/src/convert/utf16.dart
@@ -1,7 +1,7 @@
 import 'dart:convert';
 import 'dart:core';
 
-import 'package:utf/utf.dart' as utf;
+import 'package:utf_convert/utf_convert.dart' as utf;
 
 abstract class UTF16 extends Encoding {
   List<int> get bom;
@@ -37,14 +37,14 @@ class _UTF16LEDecoder extends Converter<List<int>, String> {
   @override
   String convert(List<int> input) {
     final decoder = utf.Utf16leBytesToCodeUnitsDecoder(input);
-    return String.fromCharCodes(decoder.decodeRest());
+    return String.fromCharCodes(decoder.decodeRest().cast<int>());
   }
 }
 
 class _UTF16LEEncoder extends Converter<String, List<int>> {
   @override
   List<int> convert(String input) {
-    return utf.encodeUtf16le(input, true);
+    return utf.encodeUtf16le(input, true) as List<int>;
   }
 }
 
@@ -66,13 +66,13 @@ class _UTF16BEDecoder extends Converter<List<int>, String> {
   @override
   String convert(List<int> input) {
     final decoder = utf.Utf16beBytesToCodeUnitsDecoder(input);
-    return String.fromCharCodes(decoder.decodeRest());
+    return String.fromCharCodes(decoder.decodeRest().cast<int>());
   }
 }
 
 class _UTF16BEEncoder extends Converter<String, List<int>> {
   @override
   List<int> convert(String input) {
-    return utf.encodeUtf16be(input, true);
+    return utf.encodeUtf16be(input, true) as List<int>;
   }
 }
diff --git a/lib/src/frames/frame.dart b/lib/src/frames/frame.dart
index 55653a0..4bb2dc9 100644
--- a/lib/src/frames/frame.dart
+++ b/lib/src/frames/frame.dart
@@ -12,19 +12,19 @@ import 'id3v2/default_frame.dart';
 /// Abstract implementation of id3v2 frame
 abstract class Frame<T> {
   /// Encode [key] tag with [value] to bytearray
-  List<int> encode(T value, [String key]);
+  List<int> encode(T value, [String? key]);
 
   /// Decode byte [data] to frame data map
-  MapEntry<String, T> decode(List<int> data);
+  MapEntry<String, T>? decode(List<int> data);
 }
 
-class FrameFactory<T extends Frame> {
+class FrameFactory<T extends Frame?> {
   String version;
 
   // ignore: avoid_annotating_with_dynamic
-  Frame Function(dynamic entry) _frameGetter;
+  Frame? Function(dynamic entry) _frameGetter;
 
-  Frame defaultFrame;
+  Frame? defaultFrame;
 
   FrameFactory._internal(this.version, this._frameGetter, [this.defaultFrame]);
 
@@ -40,7 +40,7 @@ class FrameFactory<T extends Frame> {
     return FrameFactory._internal('0', (v) => null);
   }
 
-  T getFrame(entry) => _frameGetter(entry);
+  Frame? getFrame(entry) => _frameGetter(entry);
 }
 
 class FramesID3V23 extends FramesID3V24 {
@@ -55,7 +55,8 @@ class FramesID3V23 extends FramesID3V24 {
 
   @override
   Frame<T> _getFrame<T>(String tag) {
-    return _frames[tag] ?? DefaultFrame(tag, version: 3);
+    return _frames[tag] as Frame<T>? ??
+        DefaultFrame(tag, version: 3) as Frame<T>;
   }
 }
 
@@ -69,16 +70,18 @@ class FramesID3V24 {
       };
 
   Frame<T> _getFrame<T>(String tag) {
-    return _frames[tag] ?? DefaultFrame(tag);
+    return _frames[tag] as Frame<T>? ?? DefaultFrame(tag) as Frame<T>;
   }
 
   String getTagByPseudonym(String tag) {
     return consts.frameHeaderShortcutsID3V2_3_Rev.containsKey(tag)
-        ? consts.frameHeaderShortcutsID3V2_3_Rev[tag]
-        : consts.framesHeaders.containsKey(tag) ? tag : 'TXXX';
+        ? consts.frameHeaderShortcutsID3V2_3_Rev[tag]!
+        : consts.framesHeaders.containsKey(tag)
+            ? tag
+            : 'TXXX';
   }
 
-  Frame<T> getFrame<T>(data) {
+  Frame<T>? getFrame<T>(data) {
     assert(data is List<int> || data is String);
 
     if (data is List<int>) {
diff --git a/lib/src/frames/id3v2/apic_frame.dart b/lib/src/frames/id3v2/apic_frame.dart
index 871bf56..8285f15 100644
--- a/lib/src/frames/id3v2/apic_frame.dart
+++ b/lib/src/frames/id3v2/apic_frame.dart
@@ -83,14 +83,14 @@ class ApicFrame extends ID3V2Frame<AttachedPicture> {
     final imageData = data.sublist(startOfImageData);
 
     final extractedImageData = _imageExtractors.containsKey(mime)
-        ? _imageExtractors[mime]().parse(imageData)
+        ? _imageExtractors[mime]!().parse(imageData)
         : imageData;
 
     return AttachedPicture(mime, imageType, description, extractedImageData);
   }
 
   @override
-  List<int> encode(AttachedPicture value, [String key]) {
+  List<int> encode(AttachedPicture value, [String? key]) {
     final mimeEncoded = latin1.encode(value.mime);
     final descEncoded = utf8.encode(value.description);
 
diff --git a/lib/src/frames/id3v2/comm_frame.dart b/lib/src/frames/id3v2/comm_frame.dart
index 5ad6f80..8f85070 100644
--- a/lib/src/frames/id3v2/comm_frame.dart
+++ b/lib/src/frames/id3v2/comm_frame.dart
@@ -42,7 +42,7 @@ class COMMFrame extends ID3V2Frame<Comment> {
   }
 
   @override
-  List<int> encode(Comment value, [String key]) {
+  List<int> encode(Comment value, [String? key]) {
     final enc = header?.encoding ?? utf8;
 
     return [
diff --git a/lib/src/frames/id3v2/default_frame.dart b/lib/src/frames/id3v2/default_frame.dart
index 697697a..71d395c 100644
--- a/lib/src/frames/id3v2/default_frame.dart
+++ b/lib/src/frames/id3v2/default_frame.dart
@@ -13,7 +13,7 @@ class DefaultFrame extends ID3V2Frame<String> {
   }
 
   @override
-  List<int> encode(String value, [String key]) {
+  List<int> encode(String value, [String? key]) {
     final tag = getTagByPseudonym(frameTag);
 
     final vBytes = utf8.encode(value);
diff --git a/lib/src/frames/id3v2/id3v2_frame.dart b/lib/src/frames/id3v2/id3v2_frame.dart
index c890992..65cdd51 100644
--- a/lib/src/frames/id3v2/id3v2_frame.dart
+++ b/lib/src/frames/id3v2/id3v2_frame.dart
@@ -25,13 +25,13 @@ abstract class ID3V2Frame<T> implements Frame<T> {
 
   final int _version;
 
-  ID3V2FrameHeader _header;
-  ID3V2FrameHeader get header => _header;
+  ID3V2FrameHeader? _header;
+  ID3V2FrameHeader? get header => _header;
 
   ID3V2Frame(this._version);
 
   @override
-  MapEntry<String, T> decode(List<int> data) {
+  MapEntry<String, T>? decode(List<int> data) {
     final tag = latin1.decode(data.sublist(0, 4));
     if (!consts.framesHeaders.keys.contains(tag)) {
       return null;
@@ -46,27 +46,27 @@ abstract class ID3V2Frame<T> implements Frame<T> {
 
     _header = ID3V2FrameHeader(tag, size, encoding: encoding);
 
-    if (data.length < headerLength + _header?.length) {
+    if (data.length < headerLength + _header!.length) {
       _header =
           ID3V2FrameHeader(tag, data.length - headerLength, encoding: encoding);
     }
 
-    final body = data.sublist(headerLength + 1, headerLength + _header?.length);
+    final body = data.sublist(headerLength + 1, headerLength + _header!.length);
 
     return MapEntry<String, T>(
-        getTagPseudonym(_header.tag), decodeBody(body, encoding));
+        getTagPseudonym(_header!.tag), decodeBody(body, encoding));
   }
 
   T decodeBody(List<int> data, Encoding enc);
 
   @override
-  List<int> encode(T value, [String key]);
+  List<int> encode(T value, [String? key]);
 
   /// Returns size of frame in bytes
   List<int> frameSizeInBytes(int value) {
     assert(value <= 16777216);
 
-    final block = List<int>(4);
+    final block = List<int>.filled(4, 0);
     final sevenBitMask = 0x7f;
 
     block[0] = (value >> 21) & sevenBitMask;
@@ -79,13 +79,13 @@ abstract class ID3V2Frame<T> implements Frame<T> {
 
   String getTagByPseudonym(String tag) {
     return consts.frameHeaderShortcutsID3V2_3_Rev.containsKey(tag)
-        ? consts.frameHeaderShortcutsID3V2_3_Rev[tag]
+        ? consts.frameHeaderShortcutsID3V2_3_Rev[tag]!
         : tag;
   }
 
   String getTagPseudonym(String tag) {
     return consts.frameHeaderShortcutsID3V2_3.containsKey(tag)
-        ? consts.frameHeaderShortcutsID3V2_3[tag]
+        ? consts.frameHeaderShortcutsID3V2_3[tag]!
         : tag;
   }
 
@@ -133,7 +133,7 @@ abstract class ID3V2Frame<T> implements Frame<T> {
 
   int indexOfSplitPattern(List<int> list, List<int> pattern,
       [int initialOffset = 0]) {
-    for (var i = initialOffset ?? 0;
+    for (var i = initialOffset;
         i < list.length - pattern.length;
         i += pattern.length) {
       final l = list.sublist(i, i + pattern.length);
@@ -182,10 +182,10 @@ class ID3V2FrameHeader {
   String tag;
   int length;
 
-  Encoding encoding;
+  Encoding? encoding;
 
   // todo: implement futher
-  int flags;
+  int? flags;
 
   ID3V2FrameHeader(this.tag, this.length, {this.flags, this.encoding}) {
     assert(consts.framesHeaders.keys.contains(tag));
diff --git a/lib/src/frames/id3v2/txxx_frame.dart b/lib/src/frames/id3v2/txxx_frame.dart
index e201765..3c52059 100644
--- a/lib/src/frames/id3v2/txxx_frame.dart
+++ b/lib/src/frames/id3v2/txxx_frame.dart
@@ -42,11 +42,11 @@ class TXXXFrame extends ID3V2Frame<String> {
   @override
   String get frameTag => 'TXXX';
 
-  String _customTagName;
+  String? _customTagName;
 
   @override
   MapEntry<String, String> decode(List<int> data) {
-    final entry = super.decode(data);
+    final entry = super.decode(data)!;
     return MapEntry<String, String>(_customTagName ?? frameTag, entry.value);
   }
 
@@ -64,7 +64,7 @@ class TXXXFrame extends ID3V2Frame<String> {
   }
 
   @override
-  List<int> encode(String value, [String key]) {
+  List<int> encode(String value, [String? key]) {
     final body = utf8.encode('$key${utf8.decode([0x00])}$value');
     return [
       ...utf8.encode(frameTag),
diff --git a/lib/src/frames/id3v2/uslt_frame.dart b/lib/src/frames/id3v2/uslt_frame.dart
index 1c60789..7de342c 100644
--- a/lib/src/frames/id3v2/uslt_frame.dart
+++ b/lib/src/frames/id3v2/uslt_frame.dart
@@ -43,7 +43,7 @@ class USLTFrame extends ID3V2Frame<UnSyncLyric> {
   }
 
   @override
-  List<int> encode(UnSyncLyric value, [String key]) {
+  List<int> encode(UnSyncLyric value, [String? key]) {
     final enc = header?.encoding ?? utf8;
 
     return [
diff --git a/lib/src/frames/id3v2/wxxx_frame.dart b/lib/src/frames/id3v2/wxxx_frame.dart
index 999d7e5..64b4e89 100644
--- a/lib/src/frames/id3v2/wxxx_frame.dart
+++ b/lib/src/frames/id3v2/wxxx_frame.dart
@@ -41,7 +41,7 @@ class WXXXFrame extends ID3V2Frame<WURL> {
   String get frameTag => 'WXXX';
 
   @override
-  List<int> encode(WURL value, [String key]) {
+  List<int> encode(WURL value, [String? key]) {
     final vBytes = [
       ...utf8.encode('${value.description}${utf8.decode([0x00])}'),
       ...latin1.encode(value.url)
diff --git a/lib/src/model/attached_picture.dart b/lib/src/model/attached_picture.dart
index 5c8fc2e..731f463 100644
--- a/lib/src/model/attached_picture.dart
+++ b/lib/src/model/attached_picture.dart
@@ -1,3 +1,5 @@
+// ignore_for_file: unnecessary_overrides
+
 import 'dart:convert';
 
 import 'key_entity.dart';
@@ -50,7 +52,7 @@ class AttachedPicture implements KeyEntity<String> {
   /// Returns [String] representation of image type.
   ///
   /// eg. 'Band/Orchestra' or 'Cover (front)' etc...
-  String get imageType => _picturesType[imageTypeCode ?? 0x00];
+  String get imageType => _picturesType[imageTypeCode];
 
   AttachedPicture(
       this.mime, this.imageTypeCode, this.description, this.imageData);
@@ -68,6 +70,9 @@ class AttachedPicture implements KeyEntity<String> {
 
   @override
   bool operator ==(other) {
+    if (other is! AttachedPicture) {
+      return false;
+    }
     if (imageTypeCode != other.imageTypeCode) {
       return false;
     }
@@ -77,9 +82,6 @@ class AttachedPicture implements KeyEntity<String> {
     if (description != other.description) {
       return false;
     }
-    if (imageData == null && other.imageData == null) {
-      return true;
-    }
     if (imageData.length != other.imageData.length) {
       return false;
     }
diff --git a/lib/src/model/comment.dart b/lib/src/model/comment.dart
index cae61a5..b136f38 100644
--- a/lib/src/model/comment.dart
+++ b/lib/src/model/comment.dart
@@ -1,3 +1,5 @@
+// ignore_for_file: unnecessary_overrides
+
 import 'key_entity.dart';
 
 /// Class describes comment entity from ID3 v2.x tags
@@ -23,6 +25,9 @@ class Comment implements KeyEntity<String> {
 
   @override
   bool operator ==(other) {
+    if (other is! Comment) {
+      return false;
+    }
     if (lang != other.lang) {
       return false;
     }
diff --git a/lib/src/model/consts.dart b/lib/src/model/consts.dart
index 051a54d..f85745a 100644
--- a/lib/src/model/consts.dart
+++ b/lib/src/model/consts.dart
@@ -1,5 +1,7 @@
 /// Generes constants from id3v1.1 specification
-final id3v1generes = const <String>[
+// ignore_for_file: constant_identifier_names
+
+const List<String> id3v1generes = <String>[
   'Blues',
   'Classic Rock',
   'Country',
@@ -130,7 +132,7 @@ final id3v1generes = const <String>[
 ];
 
 // v2.3+ frames
-final framesHeaders = const <String, String>{
+const framesHeaders = <String, String>{
   'AENC': 'Audio encryption',
   'APIC': 'Attached picture',
   'COMM': 'Comments',
@@ -228,7 +230,7 @@ final framesHeaders = const <String, String>{
   'TSST': 'Set subtitle'
 };
 
-final framesV23_V24 = const <String, String>{
+const framesV23_V24 = <String, String>{
   'EQUA': 'EQU2',
   'IPLS': 'TIPL',
   'RVAD': 'RVA2',
@@ -239,7 +241,7 @@ final framesV23_V24 = const <String, String>{
   'TYER': 'TDRC'
 };
 
-final frameHeaderShortcutsID3V2_3 = const <String, String>{
+const frameHeaderShortcutsID3V2_3 = <String, String>{
   'TIT2': 'title',
   'TPE1': 'artist',
   'TALB': 'album',
@@ -251,7 +253,7 @@ final frameHeaderShortcutsID3V2_3 = const <String, String>{
   'USLT': 'lyrics',
 };
 
-final frameHeaderShortcutsID3V2_3_Rev = const <String, String>{
+const frameHeaderShortcutsID3V2_3_Rev = <String, String>{
   'title': 'TIT2',
   'artist': 'TPE1',
   'album': 'TALB',
@@ -265,7 +267,7 @@ final frameHeaderShortcutsID3V2_3_Rev = const <String, String>{
 
 // todo support v2.2
 // ignore: unused_field
-final frameHeaderShortcutsID3V2_2 = const <String, String>{
+const frameHeaderShortcutsID3V2_2 = <String, String>{
   'TT2': 'title',
   'TP1': 'artist',
   'TAL': 'album',
@@ -279,7 +281,7 @@ final frameHeaderShortcutsID3V2_2 = const <String, String>{
 
 // todo support v2.2
 // ignore: unused_field
-final frameHeadersLegacy = const <String, String>{
+const frameHeadersLegacy = <String, String>{
   'BUF': 'RBUF',
   'COM': 'COMM',
   'CRA': 'AENC',
diff --git a/lib/src/model/lyrics.dart b/lib/src/model/lyrics.dart
index bac5f6c..24baf5c 100644
--- a/lib/src/model/lyrics.dart
+++ b/lib/src/model/lyrics.dart
@@ -1,3 +1,5 @@
+// ignore_for_file: unnecessary_overrides
+
 import 'package:dart_tags/src/model/key_entity.dart';
 
 /// Class describes unsynchronised lyrics entity from ID3 v2.x tags
@@ -23,6 +25,9 @@ class UnSyncLyric implements KeyEntity<String> {
 
   @override
   bool operator ==(other) {
+    if (other is! UnSyncLyric) {
+      return false;
+    }
     if (lang != other.lang) {
       return false;
     }
diff --git a/lib/src/model/tag.dart b/lib/src/model/tag.dart
index edb67a3..b636fcd 100644
--- a/lib/src/model/tag.dart
+++ b/lib/src/model/tag.dart
@@ -1,16 +1,21 @@
 /// Class describes tag
+// ignore_for_file: unnecessary_overrides
+
 class Tag {
   /// Type of tag. At this time supports 'id3'
-  String type;
+  String? type;
 
   /// Version of tag. eg. '2.4.0' or '1.1'
-  String version;
+  String? version;
 
   /// The map of tags. Values are dynamic because it can be not only String.
-  Map<String, dynamic> tags;
+  late Map<String, dynamic> tags;
 
   @override
   bool operator ==(other) {
+    if (other is! Tag) {
+      return false;
+    }
     if (type != other.type) {
       return false;
     }
diff --git a/lib/src/model/wurl.dart b/lib/src/model/wurl.dart
index 095be4f..b5b4da7 100644
--- a/lib/src/model/wurl.dart
+++ b/lib/src/model/wurl.dart
@@ -1,3 +1,5 @@
+// ignore_for_file: unnecessary_overrides
+
 import 'key_entity.dart';
 
 /// Class describes url from WXXX tag
@@ -20,6 +22,9 @@ class WURL implements KeyEntity<String> {
 
   @override
   bool operator ==(other) {
+    if (other is! WURL) {
+      return false;
+    }
     if (description != other.description) {
       return false;
     }
diff --git a/lib/src/readers/id3v2.dart b/lib/src/readers/id3v2.dart
index ac102cd..7ee956f 100644
--- a/lib/src/readers/id3v2.dart
+++ b/lib/src/readers/id3v2.dart
@@ -1,3 +1,5 @@
+// ignore_for_file: non_constant_identifier_names
+
 import 'dart:async';
 import 'dart:convert';
 
@@ -67,23 +69,23 @@ class ID3V2Reader extends Reader {
     while (contin) {
       final fr = bytes.sublist(offset);
 
-      final frame = ff.getFrame(fr);
+      final frame = ff.getFrame(fr)! as ID3V2Frame;
       final m = frame.decode(fr);
 
       if (m?.key != null && m?.value != null) {
         if (m?.value is KeyEntity) {
-          if (tags[m.key] == null) {
+          if (tags[m!.key] == null) {
             tags[m.key] = {m.value.key: m.value};
           } else {
             tags[m.key][m.value.key] = m.value;
           }
         } else {
-          tags[m.key] = m.value;
+          tags[m!.key] = m.value;
         }
       }
 
-      offset = offset + _headerLength + (frame?.header?.length ?? 0);
-      contin = offset < size && (frame?.header?.length ?? 0) != 0;
+      offset = offset + _headerLength + (frame.header?.length ?? 0);
+      contin = offset < size && (frame.header?.length ?? 0) != 0;
     }
 
     return tags;
diff --git a/lib/src/tag_processor.dart b/lib/src/tag_processor.dart
index 2a634ce..4b514c0 100644
--- a/lib/src/tag_processor.dart
+++ b/lib/src/tag_processor.dart
@@ -15,7 +15,7 @@ class ParsingException implements Exception {
   static const byteDataNull = 'Byte data can\'t be null';
   static const byteArrayNull = 'Byte array can\'t be null';
 
-  final cause;
+  final dynamic cause;
   ParsingException(this.cause);
 
   @override
@@ -33,9 +33,9 @@ class TagProcessor {
     TagType.id3v2: ID3V2Writer(),
   };
 
-  static TagType getTagType(String type, String version) {
+  static TagType getTagType(String type, String? version) {
     if (type.toLowerCase() == 'id3') {
-      switch (version.substring(0, 1)) {
+      switch (version!.substring(0, 1)) {
         case '1':
           return TagType.id3v1;
         case '2':
@@ -48,8 +48,8 @@ class TagProcessor {
   }
 
   /// Returns the tags from the byte array
-  Future<List<Tag>> getTagsFromByteArray(Future<List<int>> bytes,
-      [List<TagType> types]) async {
+  Future<List<Tag>> getTagsFromByteArray(Future<List<int>>? bytes,
+      [List<TagType>? types]) async {
     if (await bytes == null) {
       throw ParsingException(ParsingException.byteArrayNull);
     }
@@ -61,15 +61,15 @@ class TagProcessor {
     }
 
     for (var t in types) {
-      tags.add(await _readers[t].read(bytes));
+      tags.add(await _readers[t]!.read(bytes!.then((value) => value)));
     }
 
     return tags;
   }
 
   /// Returns the tags from the ByteData
-  Future<List<Tag>> getTagsFromByteData(ByteData bytes,
-      [List<TagType> types]) async {
+  Future<List<Tag>> getTagsFromByteData(ByteData? bytes,
+      [List<TagType>? types]) async {
     if (bytes == null) {
       throw ParsingException(ParsingException.byteDataNull);
     }
@@ -83,18 +83,18 @@ class TagProcessor {
     }
 
     for (var t in types) {
-      tags.add(await _readers[t].read(c.future));
+      tags.add(await _readers[t]!.read(c.future));
     }
 
     return tags;
   }
 
-  Future<List<int>> putTagsToByteArray(Future<List<int>> bytes,
-      [List<Tag> tags]) async {
+  Future<List<int>> putTagsToByteArray(Future<List<int>?> bytes,
+      [List<Tag>? tags]) async {
     if (await bytes == null) {
       throw ParsingException(ParsingException.byteArrayNull);
     }
-    var b = await bytes;
+    var b = (await bytes)!;
 
     if (tags == null || tags.isEmpty) {
       for (var w in _writers.values) {
@@ -105,7 +105,7 @@ class TagProcessor {
     }
 
     for (var t in tags) {
-      final w = _writers[getTagType(t.type, t.version)];
+      final w = _writers[getTagType(t.type!, t.version)]!;
       b = await w.write(b, t);
     }
 
diff --git a/lib/src/writers/id3v2.dart b/lib/src/writers/id3v2.dart
index d7c4dd9..f64b910 100644
--- a/lib/src/writers/id3v2.dart
+++ b/lib/src/writers/id3v2.dart
@@ -1,9 +1,9 @@
 import 'dart:async';
 import 'dart:convert';
 
+import 'package:dart_tags/src/frames/frame.dart';
 import 'package:dart_tags/src/model/tag.dart';
 import 'package:dart_tags/src/writers/writer.dart';
-import 'package:dart_tags/src/frames/frame.dart';
 
 class ID3V2Writer extends Writer {
   ID3V2Writer() : super('ID3', '2.4');
@@ -15,19 +15,17 @@ class ID3V2Writer extends Writer {
     final ff = FrameFactory('ID3', '2.4.0');
 
     tag.tags.forEach((k, v) {
-      if (k != null) {
-        final frame = ff.getFrame(k);
-        if (v is List) {
-          v.forEach((element) {
-            tagsF.addAll(frame?.encode(element, k));
-          });
-        } else if (v is Map) {
-          v.values.forEach((element) {
-            tagsF.addAll(frame?.encode(element, k));
-          });
-        } else {
-          tagsF.addAll(frame?.encode(v, k));
+      final frame = ff.getFrame(k)!;
+      if (v is List) {
+        for (var element in v) {
+          tagsF.addAll(frame.encode(element, k));
+        }
+      } else if (v is Map) {
+        for (var element in v.values) {
+          tagsF.addAll(frame.encode(element, k));
         }
+      } else {
+        tagsF.addAll(frame.encode(v, k));
       }
     });
 
@@ -46,7 +44,7 @@ class ID3V2Writer extends Writer {
   static List<int> frameSizeInBytes(int value) {
     assert(value <= 16777216);
 
-    final block = List<int>(4);
+    final block = List<int>.filled(4, 0);
     final sevenBitMask = 0x7f;
 
     block[0] = (value >> 21) & sevenBitMask;
diff --git a/pubspec.yaml b/pubspec.yaml
index 2aa86aa..f8c3e88 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,16 +1,16 @@
 name: dart_tags
 description: The library for work with music tags like ID3. Written on pure Dart. It can be used in flutter, web, and vm projects.
-version: 0.3.1
+version: 0.4.0
 homepage: https://github.com/NiKoTron/dart-tags
 
 environment:
-  sdk: '>=2.3.0 <3.0.0' 
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
-  utf: ^0.9.0+5
-  collection: ^1.14.13
-  convert: ^2.1.1
+  utf_convert: ^0.10.0+1
+  collection: ^1.15.0
+  convert: ^3.0.1
 
 dev_dependencies:
-  pedantic: ^1.9.2
-  test: ^1.15.3
+  lints: ^1.0.1
+  test: ^1.19.1
diff --git a/test/dart_tags_test.dart b/test/dart_tags_test.dart
index 9e2ab29..5b898f3 100644
--- a/test/dart_tags_test.dart
+++ b/test/dart_tags_test.dart
@@ -5,7 +5,6 @@ import 'dart:typed_data';
 import 'package:dart_tags/dart_tags.dart';
 import 'package:collection/collection.dart' as collection;
 import 'package:dart_tags/src/frames/id3v2/comm_frame.dart';
-import 'package:dart_tags/src/model/comment.dart';
 import 'package:dart_tags/src/readers/id3v1.dart';
 import 'package:dart_tags/src/readers/id3v2.dart';
 import 'package:dart_tags/src/utils/image_extractor.dart';
@@ -14,11 +13,11 @@ import 'package:dart_tags/src/writers/id3v2.dart';
 import 'package:test/test.dart';
 
 void main() {
-  File file1;
-  File file2;
-  File file3;
-  File filev23USLT;
-  File picture;
+  late File file1;
+  late File file2;
+  late File file3;
+  late File filev23USLT;
+  late File picture;
 
   const outputDir = 'test/output';
 
@@ -117,7 +116,7 @@ void main() {
         0x72
       ];
 
-      final decodeList = COMMFrame().decode(data);
+      final decodeList = COMMFrame().decode(data)!;
 
       expect(decodeList.value.comment, equals('commentador'));
       expect(decodeList.value.description, equals('dessu'));
@@ -227,7 +226,7 @@ void main() {
           ]),
           [tag1, tag2]);
 
-      final _fr = () async => foo;
+      Future<List<int>> _fr() async => foo;
 
       final rdr1 = ID3V1Reader();
       final t1 = await rdr1.read(_fr());
@@ -407,7 +406,7 @@ void main() {
           ]),
           [tag2]);
 
-      final _fr = () async => foo;
+      Future<List<int>> _fr() async => foo;
 
       final rdr2 = ID3V2Reader();
       final t2 = await rdr2.read(_fr());
@@ -474,7 +473,7 @@ void main() {
       final f = await r.read(blocks);
 
       // ignore: avoid_as
-      final AttachedPicture pic = (f.tags['picture'] as Map)['Other'];
+      final AttachedPicture? pic = (f.tags['picture'] as Map)['Other'];
       expect(pic, equals(pic1));
     });
 
@@ -487,7 +486,6 @@ void main() {
           .getTagsFromByteArray(file.readAsBytes(), [TagType.id3v2]);
 
       expect(tags.length, 1);
-      expect(tags[0] != null, true);
       expect(tags[0].type, 'ID3');
       expect(tags[0].version, '2.3.0');
       expect(tags[0].tags.isNotEmpty, true);
diff --git a/tool/assets/dart-tags-logo.svg b/tool/assets/dart-tags-logo.svg
new file mode 100644
index 0000000..f2103a4
--- /dev/null
+++ b/tool/assets/dart-tags-logo.svg
@@ -0,0 +1,176 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="43.358593mm"
+   height="43.476334mm"
+   viewBox="0 0 43.358593 43.476334"
+   version="1.1"
+   id="svg8"
+   inkscape:version="0.92.5 (2060ec1f9f, 2020-04-08)"
+   sodipodi:docname="dart-tags-lol.svg">
+  <defs
+     id="defs2">
+	
+	
+
+		
+		
+		
+		
+		
+		
+		
+		
+
+			<radialGradient
+   gradientUnits="userSpaceOnUse"
+   gradientTransform="matrix(0.26458333,0,0,-0.26458333,1.5646202,66.72568)"
+   r="68.065002"
+   cy="60.886398"
+   cx="69.955002"
+   id="SVGID_1_">
+			<stop
+   id="stop3737"
+   style="stop-color:#FFFFFF;stop-opacity:0.1"
+   offset="0" />
+
+			<stop
+   id="stop3739"
+   style="stop-color:#FFFFFF;stop-opacity:0"
+   offset="1" />
+
+		</radialGradient>
+
+		
+	</defs>
+  <sodipodi:namedview
+     id="base"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:pageopacity="0.0"
+     inkscape:pageshadow="2"
+     inkscape:zoom="2.56"
+     inkscape:cx="-1.9377281"
+     inkscape:cy="38.263417"
+     inkscape:document-units="mm"
+     inkscape:current-layer="layer1"
+     showgrid="false"
+     showguides="true"
+     inkscape:guide-bbox="true"
+     inkscape:window-width="3840"
+     inkscape:window-height="2029"
+     inkscape:window-x="0"
+     inkscape:window-y="70"
+     inkscape:window-maximized="1"
+     inkscape:pagecheckerboard="true"
+     borderlayer="false"
+     fit-margin-top="0"
+     fit-margin-left="0"
+     fit-margin-right="0"
+     fit-margin-bottom="0">
+    <sodipodi:guide
+       position="29.617457,7.4638962"
+       orientation="-0.70710678,0.70710678"
+       id="guide4609"
+       inkscape:locked="false"
+       inkscape:label=""
+       inkscape:color="rgb(0,0,255)" />
+    <sodipodi:guide
+       position="14.689666,7.4638962"
+       orientation="0.70710678,0.70710678"
+       id="guide4611"
+       inkscape:locked="false"
+       inkscape:label=""
+       inkscape:color="rgb(0,0,255)" />
+    <sodipodi:guide
+       position="36.012436,28.551186"
+       orientation="0.70710678,0.70710678"
+       id="guide4613"
+       inkscape:locked="false"
+       inkscape:label=""
+       inkscape:color="rgb(0,0,255)" />
+    <sodipodi:guide
+       position="29.617457,13.858876"
+       orientation="0.70710678,0.70710678"
+       id="guide4615"
+       inkscape:locked="false"
+       inkscape:label=""
+       inkscape:color="rgb(0,0,255)" />
+    <sodipodi:guide
+       position="0.31507899,22.843626"
+       orientation="-0.70710678,0.70710678"
+       id="guide4619"
+       inkscape:locked="false"
+       inkscape:label=""
+       inkscape:color="rgb(0,0,255)" />
+  </sodipodi:namedview>
+  <metadata
+     id="metadata5">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title></dc:title>
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <g
+     inkscape:label="Layer 1"
+     inkscape:groupmode="layer"
+     id="layer1"
+     transform="translate(-2.0620369,-32.609564)">
+    <g
+       id="g4629">
+      <path
+         style="fill:#40c4ff;fill-opacity:1;stroke-width:0.26458332"
+         inkscape:connector-curvature="0"
+         d="m 9.4068701,61.277168 -6.1594999,-6.1595 c -0.73025,-0.751417 -1.1853333,-1.80975 -1.1853333,-2.844271 0,-0.478896 0.269875,-1.227666 0.4736041,-1.658937 L 8.2215368,38.769064 Z"
+         id="path3721" />
+      <path
+         style="fill:#01579b;fill-opacity:1;stroke-width:0.26458332"
+         inkscape:connector-curvature="0"
+         d="m 30.494162,39.954397 -6.1595,-6.1595 c -0.537105,-0.53975 -1.658938,-1.185333 -2.606146,-1.185333 -0.814917,0 -1.613959,0.164042 -2.132542,0.473604 L 8.2241826,38.769064 Z"
+         id="path3723" />
+      <path
+         sodipodi:nodetypes="scccccs"
+         style="fill:#40c4ff;fill-opacity:1;stroke-width:0.26458332"
+         inkscape:connector-curvature="0"
+         d="m 8.2241826,57.961939 c 0,1.899708 0.238125,2.368021 1.1853333,3.317875 L 24.215599,76.085897 34.876985,65.424511 21.254912,50.381626 8.2241826,38.77171 Z"
+         id="path3727" />
+      <path
+         sodipodi:nodetypes="scccccs"
+         style="fill:#01579b;stroke-width:0.26458332"
+         inkscape:connector-curvature="0"
+         d="M 27.176287,38.769064 H 8.2215368 L 34.876985,65.424511 45.420629,54.880866 38.074474,47.53471 30.494162,39.954397 c -1.063625,-1.068916 -2.010834,-1.185333 -3.317875,-1.185333 z"
+         id="path3729" />
+    </g>
+    <path
+       style="fill:#ffffff;fill-opacity:0.96065572;stroke-width:0.26458332"
+       d="m 14.249261,43.100254 a 1.6536458,1.6536458 0 0 1 -1.653646,1.653646 1.6536458,1.6536458 0 0 1 -1.653645,-1.653646 1.6536458,1.6536458 0 0 1 1.653645,-1.653646 1.6536458,1.6536458 0 0 1 1.653646,1.653646 z"
+       id="path4617"
+       inkscape:connector-curvature="0" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:10.58333302px;line-height:1.25;font-family:sans-serif;letter-spacing:0px;word-spacing:0px;fill:#ffffff;fill-opacity:1;stroke:none;stroke-width:0.26458332"
+       x="-31.532589"
+       y="65.593918"
+       id="text4623"
+       transform="rotate(-45)"><tspan
+         sodipodi:role="line"
+         id="tspan4621"
+         x="-31.532589"
+         y="65.593918"
+         style="fill:#ffffff;fill-opacity:1;stroke-width:0.26458332">tags</tspan></text>
+  </g>
+</svg>
diff --git a/tool/travis/swag.sh b/tool/travis/swag.sh
index 697a9e2..0e7251d 100755
--- a/tool/travis/swag.sh
+++ b/tool/travis/swag.sh
@@ -3,7 +3,7 @@
 pub get || exit $
 
 EXIT_CODE=0
-dartfmt -n --set-exit-if-changed . || EXIT_CODE=$?
+dart format --fix --set-exit-if-changed . || EXIT_CODE=$?
 dartanalyzer --fatal-infos --fatal-warnings . || EXIT_CODE=$?
 
 exit $EXIT_CODE