upi_kit

Try the live playground: create a UPI QR code, or paste a scanned one to see what's inside

Build, parse and validate the two kinds of payment QR code used in India: UPI links (upi://pay?pa=…) and Bharat QR (EMV) codes.

final link = UpiPaymentLink(
  payeeVpa: 'sharmastores@okicici',
  payeeName: 'Sharma Stores',
  amount: UpiAmount.parse('149.50'),
  transactionRef: 'ORD1043',
);
print(link); // upi://pay?pa=sharmastores@okicici&pn=Sharma%20Stores&tr=ORD1043&am=149.50&cu=INR

Most UPI packages open a payment app for you. This one handles the data itself, so you can create links and QR codes, read what a scanner returns, and catch mistakes before a payer sees "invalid QR":

• Correct encoding: spaces become %20, not + (some apps show a literal +), and amounts always have two decimal places
• Bharat QR (EMV): read and write the ID-length-value format, with CRC-16 checking, so a misread code is caught instead of paid
• Validation that explains itself: a bad UPI ID, a zero amount, a minimum above the amount, a non-INR currency or a four-digit MCC that isn't one, each with a field name and a readable message
• No floating point money: UpiAmount keeps whole paise, so 0.1 + 0.2 is exactly ₹0.30
• iOS links: iOS has no app chooser for upi://, so toLink(UpiApp.phonePe) gives you phonepe://pay?… and the same for Google Pay and Paytm
• Pure Dart, no dependencies: works in Flutter apps, on the web and on your server

Install

dart pub add upi_kit

Usage

Make a payment link or QR code

import 'package:upi_kit/upi_kit.dart';

final link = UpiPaymentLink(
  payeeVpa: 'sharmastores@okicici',
  payeeName: 'Sharma Stores',
  amount: UpiAmount.parse('149.50'),
  note: 'Order 1043',
  transactionRef: 'ORD1043',
);

final issues = link.validate();   // [] when payment apps will accept it
final qrText = link.toLink();     // put this in a QR code

Draw the QR code with any QR widget, for example qr_flutter:

QrImageView(data: link.toLink(), size: 220)

Open a UPI app

With url_launcher:

// Android shows the payer a list of UPI apps.
await launchUrl(link.toUri(), mode: LaunchMode.externalApplication);

// iOS needs a specific app. Add the schemes you use
// (gpay, phonepe, paytmmp) to LSApplicationQueriesSchemes in Info.plist.
await launchUrl(link.toUri(UpiApp.phonePe), mode: LaunchMode.externalApplication);

Make a Bharat QR code

final qr = EmvQr.bharatQr(
  vpa: 'sharmastores@okicici',
  merchantName: 'Sharma Stores',
  merchantCity: 'Bengaluru',
  merchantCategoryCode: '5411',
  amount: UpiAmount.parse('149.50'),   // leave out for a reusable shop code
  transactionRef: 'ORD1043',
);
print(qr.payload); // 00020101021226380010A0000005240120sharmastores@okicici...6304AEDA

The point of initiation (11 reusable, 12 one-time), the currency (356), the country, field lengths and the CRC are all filled in for you.

Read a scanned code

Hand UpiQr.parse whatever your scanner returns (mobile_scanner, for example) and switch on the result:

final scanned = UpiQr.tryParse(barcode.rawValue ?? '');
if (scanned == null) return showError('Not a payment QR code');

switch (scanned) {
  case UpiLinkQr(:final link):
    print('Pay ${link.payeeName} at ${link.payeeVpa}');
  case EmvUpiQr(:final qr):
    print('Pay ${qr.merchantName} in ${qr.merchantCity}, ref ${qr.upi?.transactionRef}');
}

// Either way, as one link you can open or store:
final link = scanned.toPaymentLink();

EmvQr.parse throws a FormatException with a clear message when the CRC doesn't match, which almost always means the code was misread or tampered with.

What's supported

	Build	Parse	Validate
UPI link: pa, pn, am, mam, tn, tr, tid, mc, cu, url, mode, purpose	✅	✅	✅
Unknown UPI parameters (sign, orgid and others)	kept in order	kept in order
Upper-case links (UPI://PAY?PA=…) and + for spaces		✅
App-specific links for iOS: Google Pay, PhonePe, Paytm	✅
EMV fields 00–99, nested templates, Unicode names	✅	✅
Bharat QR UPI fields: 26 (UPI ID, minimum amount), 27 (reference, URL)	✅	✅	✅
EMV additional data (62): bill number, store, terminal, purpose…	✅	✅
CRC-16/CCITT-FALSE (field 63)	✅	✅
Required EMV fields: 52, 53, 58, 59, 60			✅

The EMV parser is tested against the worked example in the EMVCo specification, including its Chinese alternate-language template.

What it doesn't do

• It doesn't move money or confirm payments. A UPI link only opens the payer's app. To know whether a payment went through, use your payment gateway's webhook or status API, never the app's return value alone.
• It can't check that a UPI ID exists. Only a payment app or a verification API can.
• Payer apps set their own limits. Some refuse person-to-person links with a pre-filled amount, or links from unverified merchants. For a business, get merchant UPI IDs and dynamic QR codes from your bank or payment gateway, and use this package to build, check and read them.

Contributing

Bug reports with a real (redacted) QR payload are especially welcome: open an issue or start a discussion.

dart test                 # VM
dart test -p chrome       # web
cd demo && flutter run -d chrome

License

MIT. See LICENSE.

Related: india_validators for PAN, GSTIN, Aadhaar, IFSC and other Indian identifiers.