BIP: 72
  Title: bitcoin: uri extensions for Payment Protocol
  Author: Gavin Andresen 
  Status: Draft
  Type: Standards Track
  Created: 29-07-2013
==Abstract== This BIP describes an extension to the bitcoin: URI scheme (BIP 21) to support the payment protocol (BIP 70). ==Motivation== Allow users to click on a link in a web page or email to initiate the payment protocol, while being backwards-compatible with existing bitcoin wallets. ==Specification== The bitcoin: URI scheme is extended with an additional, optional "r" parameter, whose value is a URL from which a PaymentRequest message should be fetched (characters not allowed within the scope of a query parameter must be percent-encoded as described in RFC 3986 and bip-0021). If the "r" parameter is provided and backwards compatibility is not required, then the bitcoin address portion of the URI may be omitted (the URI will be of the form: bitcoin:?r=... ). When Bitcoin wallet software that supports this BIP receives a bitcoin: URI with a request parameter, it should ignore the bitcoin address/amount/label/message in the URI and instead fetch a PaymentRequest message and then follow the payment protocol, as described in BIP 70. Bitcoin wallets must support fetching PaymentRequests via http and https protocols; they may support other protocols. Wallets must include an Accept HTTP header in HTTP(s) requests: 
Accept: application/bitcoin-paymentrequest
If a PaymentRequest cannot be obtained (perhaps the server is unavailable), then the customer should be informed that the merchant's payment processing system is unavailable. ==Compatibility== Wallet software that does not support this BIP will simply ignore the r parameter and will initiate a payment to bitcoin address. ==Examples== A backwards-compatible request: 
bitcoin:mq7se9wy2egettFxPbmn99cK8v5AFq55Lx?amount=0.11&r=https://merchant.com/pay.php?h%3D2a8628fc2fbe
Non-backwards-compatible equivalent: 
bitcoin:?r=https://merchant.com/pay.php?h%3D2a8628fc2fbe