Beta

Payment Processor API

Accept invoices, track confirmations, and handle payment webhooks.

advanced2 weeksproject // payment-processor

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Learning objectives

Create BIP-21 payment requests with unique addresses or amounts
Detect payments and confirmation thresholds
Emit signed webhooks to merchants

study // plan

Lessons are primers. Start with Step 1 (required reading) when present, then follow the numbered steps in the article. Depth comes from primary sources, labs, reflection, and evidence.

Research on Bitcoin Search

Step 1 // Required reading

Complete these before the numbered steps in the lesson body. Links are listed here once — not repeated below.

docsProject Spec: Payment Processor
Pull project page — acceptance criteria and submit flow.
bipBIP-21 URI scheme

Reflection prompts

Explain Payment Processor API to a teammate without jargon - what problem does it solve?
What would break in production if you misunderstood Payment Processor API?
Which BIP, book chapter, or Core doc is authoritative here, and what did you verify?

Lab // Project milestone evidence

Complete Steps 2–4. Ship invoice create → detect → confirm → webhook on regtest and capture demo evidence before marking complete.

evidence required

Link to public repo or branch
Demo of create invoice + paid/confirmed status (commands or screenshots)
Short note of one failure case (underpay, expiry, webhook retry)

Merchants need idempotent invoices, confirmation policies, and reliable callbacks. This project is the on-chain cousin of a Lightning POS.

Complete Step 1 // Required reading in the study plan above, then continue here. This closes Projects.

Step 2 — Goal

API endpoints to:

Create invoice (amount, expiry, address)
Query invoice status
Register webhook URL
Mark paid after N confirmations

Return a BIP-21 URI with the invoice details.

Loading diagram…

Invoice creation, detection, confirmation, webhook.

Done when: You can explain idempotency for “create invoice” retries.

Step 3 — Milestones

Phase	Ship
Milestone A	Create + get invoice with unique address / BIP-21
Milestone B	Detect payment and confirmation threshold on regtest
Milestone C	Signed webhook + under/over-payment policy documented

Chapter review picks

Practice on real Bitcoin OSS changes tied to this chapter. Read the diff, use the checklist, and optionally paste your review comment URL in your lab notes.

BTCPay Server payment flow GFI
Study how BTCPay tracks invoices and note parallels to the payment processor project spec.
gfi
BIP-21confirmation tracking
35 min·intermediateopen on GitHub
Mempool.space explorer GFI
Compare mempool.space's fee views with what you'd build in the block explorer project.
gfi
UXfee visualization
30 min·beginneropen on GitHub
BDK documentation pull requests
Review a BDK docs PR and note whether examples would help a mini-wallet builder.
pr review
examplesAPI clarity
35 min·beginneropen on GitHub

review checklist

Does the change solve the stated problem?
Are edge cases and rollout behavior covered?
Are tests or test vectors included?
Is the diff minimal and clearly explained?

More repos and GFIs on /discover and /issues.

build // next

Apply this chapter in a project

You have the concepts — ship something small to prove it. These Pull projects connect directly to what you just studied.

project // mini-wallet
./spec ./submit
project // payment-processor
./spec ./submit

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Payment Processor API

Learning objectives

Step 1 // Required reading

Reflection prompts

Lab // Project milestone evidence

How to study this lesson

Step 2 — Goal

Step 3 — Milestones

further reading

Chapter review picks

Apply this chapter in a project

Step 4 — Build & evidence (lab)

Common mistakes

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