Show HN: ProofOfDonation, replace CAPTCHAs with charity donations

Developer mgriley launched ProofOfDonation, a self-hosted server designed as an experimental alternative to CAPTCHA verification. Instead of requiring users to solve puzzles, the system gates signups on confirmed charity donations, verifying email donation receipts using DKIM authentication.

The tool works by accepting donation proof from users—typically email receipts from charities—and cryptographically validating those receipts before allowing account access. By linking account creation to charitable giving rather than puzzle-solving, ProofOfDonation aims to eliminate the friction of traditional CAPTCHAs while routing user friction toward a charitable outcome. The project is open-source and available for self-hosting, meaning individual sites or platforms can integrate it into their own signup flows.

The motivation behind the project is straightforward: CAPTCHAs protect against bots and abuse, but they create friction for legitimate users. ProofOfDonation sidesteps that tension by replacing the puzzle with a proof-of-stake mechanism grounded in real-world charitable action. The approach assumes that spam actors are less likely to donate to charities to bypass verification than legitimate users are willing to donate in exchange for frictionless access. The project uses DKIM verification, a standard email authentication protocol, to ensure donation receipts are authentic and haven't been forged.

This sits in a broader category of proof-of-work alternatives to CAPTCHAs. Proof-of-Donation aligns philosophically with systems that tie verification to some real cost or action—whether computational (mining), financial (payment), or social (charity). The practical challenge will be adoption: platforms must be willing to gate access on user donations, and users must accept that frictionless signup now carries an expectation of giving. The approach also depends on widespread adoption by charities to issue verifiable email receipts with DKIM signatures.