<pre>
  BIP: 72
  Title: bitcoin: uri extensions for Payment Protocol
  Author: Gavin Andresen <gavinandresen@gmail.com>
  Status: Draft
  Type: Standards Track
  Created: 2013-07-29
</pre>

==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:
<pre>Accept: application/bitcoin-paymentrequest</pre>

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:
<pre>
bitcoin:mq7se9wy2egettFxPbmn99cK8v5AFq55Lx?amount=0.11&r=https://merchant.com/pay.php?h%3D2a8628fc2fbe
</pre>
Non-backwards-compatible equivalent:
<pre>
bitcoin:?r=https://merchant.com/pay.php?h%3D2a8628fc2fbe
</pre>
