flutter_chardet

Detect the character encoding of text bytes in Flutter, then optionally convert those bytes into a Dart String.

This is useful when your app opens files, subtitles, logs, crawled pages, or other text that is not guaranteed to be UTF-8.

flutter_chardet uses the native uchardet detector through FFI. When you call autoDecode, the byte-to-string conversion is handled by charset_converter.

Install

flutter pub add flutter_chardet

Supported Platforms

Platform	Detect charset	Detect and convert to `String`
Android	Yes	Yes
iOS	Yes	Yes
macOS	Yes	Yes
Windows	Yes	Yes
Linux	Yes	Yes
Web	No	No

Web is not supported because detection uses native code. Conversion support is provided by charset_converter, which supports Android, iOS, macOS, Windows, and Linux.

Usage

Only Detect

Use detect when you only need the most likely charset name.

import 'dart:io';

import 'package:flutter_chardet/flutter_chardet.dart';

final bytes = await File('example.txt').readAsBytes();
final charset = await FlutterChardet.detect(bytes);

print(charset);

Possible output:

UTF-8

Other common outputs include SHIFT_JIS, windows-1251, Big5, EUC-JP, and ISO-8859-1. Very short text can be ambiguous, so treat the result as a best guess rather than a promise.

Detect and Convert to String

Use autoDecode when you want a decoded Dart String and the detection details that were used for conversion.

import 'dart:io';

import 'package:flutter_chardet/flutter_chardet.dart';

final bytes = await File('subtitle.srt').readAsBytes();
final result = await FlutterChardet.autoDecode(bytes);

print(result.text);
print(result.charset);
print(result.confidence);
print(result.language);

Possible output:

こんにちは
SHIFT_JIS
0.99
ja

The returned DecodingResult contains:

Field	Meaning
`text`	Decoded Dart `String`
`charset`	Charset detected before conversion
`encoding`	Alias for `charset`
`confidence`	Detector confidence for the selected charset
`language`	Detected language code when available

Compared with flutter_charset_detector

flutter_charset_detector is another Flutter package that can detect and decode text encodings. The table below uses the upstream uchardet fixtures in test/upstream as a reference set. A decoded string only counts as correct when it matches an independent UTF-8 conversion.

Package	Supported platforms	Correct charset detection	Correct decoded text	Small text `autoDecode`	Large text `autoDecode`	Minimal Android APK	Minimal iOS app
`flutter_chardet`	Android, iOS, macOS, Windows, Linux	152 / 158	148 / 158	0.125 ms	142.7 ms	14.1 MB	12.4 MB
`flutter_charset_detector` 6.0.0	Android, iOS, macOS, Web	146 / 158	145 / 158	0.117 ms	278.7 ms	13.9 MB	19.9 MB

On this fixture set, flutter_chardet detects and decodes more cases correctly. For very small text the two packages are similar. For the large Shift_JIS sample, flutter_chardet was faster in the local benchmark.

Detailed result files are kept in the GitHub repository:

Notes

Detection is only a guess. If your format already declares an encoding, prefer that explicit value. Use charset detection when the input does not tell you what it is.