Definition
BIP70 was an ambitious payment protocol designed to make Bitcoin payments to merchants safer and more informative than pasting a raw address. Instead of paying to an opaque 34-character string, a customer's wallet would fetch a signed PaymentRequest from the merchant, exchange Payment and PaymentACK messages, and receive a cryptographic receipt. Understanding it matters mainly so you recognize why it is no longer used.
What it tried to solve
BIP70 used X.509 TLS certificates to bind a payment to a verifiable identity, so a wallet could display "example.com" rather than a meaningless address. It aimed to defeat man-in-the-middle address-swapping, provide proof of payment for disputes, and let merchants supply refund addresses automatically. The messages were encoded with Google Protocol Buffers and delivered over HTTP/HTTPS.
Why it was abandoned
In practice the design proved heavy and fragile. Reliance on the centralized X.509 certificate authority system reintroduced exactly the kind of trusted third party Bitcoin exists to avoid, and several wallets shipped implementation flaws. Bitcoin Core added deprecation warnings in v0.18, disabled the protocol by default in v0.19 (2019), and later removed support entirely (PR #17165). Modern guidance directs everyone to simpler, trust-minimized alternatives.
The practical replacement for everyday payments is the lightweight BIP21 Bitcoin URI scheme, which carries amount and label data without any certificate machinery. We note BIP70 here for historical accuracy; sovereign users should not deploy it.
In Simple Terms
BIP70 was an ambitious payment protocol designed to make Bitcoin payments to merchants safer and more informative than pasting a raw address. Instead of paying…