ALTCHA Flutter Widget #

The AltchaWidget is a CAPTCHA-like Flutter component that provides a secure, privacy-friendly way to verify that a user is human—without annoying them. It uses a cryptographic proof-of-work mechanism combined with an optional code challenge, making it resilient against bots and spam.

ALTCHA is an open-source alternative to traditional CAPTCHA, designed to be fast, accessible, and privacy-respecting.

For more information and documentation, visit altcha.org.

Features #

• Native Flutter widget – no WebView required
• Privacy-friendly, CAPTCHA-like verification
• Supports image and audio code challenge with ALTCHA Sentinel (adaptive CAPTCHA)
• Localizations support

Screenshots #

Installation #

Add the following to your pubspec.yaml:

dependencies:
  altcha_widget:
    git:
      url: https://github.com/altcha-org/altcha-flutter.git

Or, if published on pub.flutter-io.cn:

dependencies:
  altcha_widget: ^1.0.0

Then run:

flutter pub get

Usage #

import 'package:altcha_widget/widget.dart';

AltchaWidget(
  challengeUrl: 'https://api.example.com/altcha/challenge',
  debug: true,
  onVerified: (payload) {
    // Send the payload to your backend
    print('Payload: $payload');
  },
)

Parameters #

One of the challengeUrl or challengeJson is required. Receive the ALTCHA payload, that you send to the server, via onVerified.

Localization #

To support different languages, include AltchaLocalizationsDelegate:

import 'package:altcha_widget/localizations.dart';

return MaterialApp(
  localizationsDelegates: [
    AltchaLocalizationsDelegate(),
    GlobalMaterialLocalizations.delegate,
    GlobalWidgetsLocalizations.delegate,
    GlobalCupertinoLocalizations.delegate,
  ],
  supportedLocales: const [
    Locale('en'),
    Locale('de'),
    Locale('es'),
    Locale('fr'),
    Locale('it'),
    Locale('pt'),
  ],
  ...
);

You can also override or add your own translations using AltchaLocalizationsDelegate(customTranslations):

return MaterialApp(
  localizationsDelegates: [
    AltchaLocalizationsDelegate(
      customTranslations: {
        'en': {
          // Define translations keys here
          'label': 'I am human',
        },
      },
    ),
    GlobalMaterialLocalizations.delegate,
    GlobalCupertinoLocalizations.delegate,
    GlobalWidgetsLocalizations.delegate,
  ],
  ...
);

Example App #

cd example/
flutter run

License #

MIT License