L402 Launch Checker
Check any API endpoint for Lightning Network 402 support in seconds. No setup, no code changes, no commitments.
Common Use Cases
- Podcast feeds — gate access to episodes with Lightning payments
- API paywalls — meter usage and charge per request with sats
- Content APIs — monetize data feeds and digital assets
- Microservices — add payment auth to internal service calls
Built for the L402 Ecosystem
Launch Checker is built by the team behind Alby and the L402 protocol spec. The same tooling used to validate L402 implementations is now available for anyone.
Used by developers integrating Lightning payments into production APIs — from indie podcasters to infrastructure teams.
What It Does
The L402 Launch Checker probes your API endpoint and tells you whether it is ready to accept Lightning payments via the L402 protocol. It runs a series of automated checks:
- Reachability - Can the endpoint be contacted?
- Method Support - Does it accept GET or POST?
- Challenge Detection - Does it respond with L402-style authentication challenges?
- Content Signals - Does the response contain L402 invoice or payment fields?
Run a preflight check in under 5 seconds. Run a full scan after payment to get a detailed report with actionable fixes.
How It Works
1. Enter Your Endpoint
Provide the URL of the API endpoint you want to check and the HTTP method you use to call it.
2. Run a Preflight Check
Our lightweight probe sends a single request to your endpoint and analyzes the response for L402 signals. You will get an immediate classification:
- Supported - Your endpoint shows clear L402 behavior
- Unsupported - No L402 signals detected
- Unclear - The probe could not confirm either way
3. Run a Full Scan (After Payment)
A full scan executes the complete L402 flow against your endpoint:
- Detects the exact challenge response format
- Parses the invoice from the 402 response
- Verifies payment hash consistency
- Captures a full transcript of the exchange
- Generates a prioritized fix list if something is not working
What You Get
| Preflight | Full Scan | |
|---|---|---|
| Reachability check | Yes | Yes |
| Method validation | Yes | Yes |
| Challenge detection | Yes | Yes |
| Invoice parsing | - | Yes |
| Payment verification | - | Yes |
| Transcript capture | - | Yes |
| Fix recommendations | - | Yes |
When to Run the Paid Scan
Run the full scan when you want a complete diagnostic — not just a yes/no signal. The paid scan:
- Detects the exact format of the L402 challenge your endpoint returns
- Parses the invoice and verifies the payment hash consistency
- Captures a full transcript of the L402 exchange
- Generates a prioritized fix list ranked by impact
If the preflight says "unsupported" or "unclear," the paid scan tells you exactly why and what to change.
Pricing
- Preflight check: Free
- Full scan: 49 sats per scan
Launch pricing: Full scan is 49 sats — below cost to validate demand.
Full scan: 49 sats per scan
Scans are capped. You set the maximum spend before running. If the scan exhausts your cap, you pay only what was actually spent.
FAQ
- What if my endpoint is not L402-ready yet?
- That is the most common outcome and exactly when the paid scan is most useful. It tells you exactly what is missing and how to fix it.
- How is this different from reading the L402 spec?
- The spec describes what L402 should do. The scan tells you what your implementation actually does and where it diverges.
- How long does the scan take?
- Usually under 10 seconds. You set a max spend cap so costs are controlled.
- What does the paid scan give me that the free preflight does not?
- Extended challenge-response testing, invoice parsing and verification, full transcript capture, and a prioritized fix list with exact guidance.