About

A misconfigured Bitcoin payment request costs the sender their funds or causes indefinite delays. Address formats vary between Legacy (1...), SegWit (bc1q...), and Taproot (bc1p...), each with distinct checksum algorithms. This tool validates the address structure using Base58Check with double SHA-256 or Bech32/Bech32m polymod verification, then encodes a BIP21-compliant URI into a QR code matrix computed entirely in your browser. No data leaves your device.

The generated QR follows ISO/IEC 18004 with byte-mode encoding and error correction level M (recovers up to 15% damage). Optional fields for amount (in BTC, not satoshis), label, and message are appended per BIP21 query parameters. Note: this tool does not verify that the address exists on-chain or has ever received funds. It validates format and checksum only.

Formulas

The BIP21 payment URI is constructed as follows:

URI = bitcoin:address[?amount=n&label=s&message=s]

Where address is a validated Bitcoin address, n is the amount in BTC (decimal, e.g., 0.001), and s are URI-encoded strings.

Base58Check validation computes:

checksum = SHA256(SHA256(payload))[0:4]

Where payload is the version byte concatenated with the 20-byte hash. The last 4 bytes of the decoded address must match checksum.

Bech32 validation uses a polymod function over GF(2³⁰):

polymod = n∑i=0 v_i ⋅ g_i mod 2³⁰

For valid Bech32, polymod = 1. For Bech32m (Taproot), polymod = 0x2bc830a3.

QR code capacity for byte mode at version v with error correction M:

modules = 21 + 4 × (v − 1)

Where v ranges from 1 to 40, yielding grids from 21×21 to 177×177 modules.

Reference Data

Address Type	Prefix	Length (chars)	Encoding	Checksum	BIP Standard	Example Prefix	Avg. Fee Impact
P2PKH (Legacy)	1	25 - 34	Base58Check	Double SHA-256 (4 bytes)	BIP-13	1A1zP1...	Highest
P2SH (Script Hash)	3	34	Base58Check	Double SHA-256 (4 bytes)	BIP-16	3J98t1...	High
P2WPKH (Native SegWit)	bc1q	42	Bech32	Polymod (6 chars)	BIP-84/141/173	bc1qw5...	Low
P2WSH (SegWit Script)	bc1q	62	Bech32	Polymod (6 chars)	BIP-141/173	bc1qr...	Low
P2TR (Taproot)	bc1p	62	Bech32m	Polymod m (6 chars)	BIP-86/341/350	bc1pw...	Lowest
Testnet P2PKH	m or n	25 - 34	Base58Check	Double SHA-256	-	mzBc4...	N/A
Testnet P2SH	2	34	Base58Check	Double SHA-256	-	2MzQw...	N/A
Testnet SegWit	tb1q	42 - 62	Bech32	Polymod	BIP-173	tb1qw...	N/A
Testnet Taproot	tb1p	62	Bech32m	Polymod m	BIP-350	tb1p0...	N/A
QR Error Correction L	Recovery: 7%		Smallest QR, least redundancy		-	-	-
QR Error Correction M	Recovery: 15%		Default. Good balance of size and resilience		ISO 18004	-	-
QR Error Correction Q	Recovery: 25%		Recommended if printing on rough surfaces		ISO 18004	-	-
QR Error Correction H	Recovery: 30%		Largest QR, survives heavy damage		ISO 18004	-	-
BIP21 URI Scheme	bitcoin:		Wallet auto-fills address, amount, label		BIP-21	-	-

Frequently Asked Questions

BIP21 URIs (e.g., bitcoin:bc1q...?amount=0.01) allow wallets to auto-populate the amount, label, and message fields when scanned. A raw address QR requires the sender to manually enter the amount, increasing the risk of typos. Most modern wallets (Electrum, BlueWallet, Sparrow) parse BIP21 natively.

The tool runs full checksum validation before generating the QR. For Legacy/P2SH addresses, it decodes Base58 and verifies the double-SHA-256 checksum bytes. For SegWit/Taproot, it runs the Bech32/Bech32m polymod check. If validation fails, no QR is produced and a specific error message identifies the issue (wrong checksum, invalid character, incorrect length).

Yes. Level M (default, 15% recovery) works for clean prints on white paper. If the QR will be printed on textured materials, affixed outdoors, or partially obscured by a logo, use level Q (25%) or H (30%). Higher correction increases QR module count and physical size. For a typical BIP21 URI of ~70 characters, level M produces a version 5 QR (37×37 modules).

Per BIP21, the amount parameter is always denominated in BTC as a decimal string. For example, 100,000 satoshis is entered as 0.001 BTC. The tool validates that the amount is a positive number with no more than 8 decimal places (1 satoshi = 0.00000001 BTC). Entering satoshi values directly would produce an incorrect payment request.

Yes. Testnet addresses starting with m, n, or 2 (Base58Check) and tb1q or tb1p (Bech32/Bech32m) are recognized and validated. The BIP21 URI will still use the bitcoin: scheme as most testnet wallets accept it, though some may require manual protocol handling.

Each QR module should be at least 0.75mm for close-range phone scanning. A version 5 QR (37×37 modules) at 0.75mm/module yields approximately 28mm × 28mm. For scanning at arm's length (~40cm), target 1.5mm per module (56mm total). The download function exports at 1024×1024 pixels, sufficient for prints up to ~130mm at 200 DPI.