Klarna API
Klarna's payment API enables buy-now-pay-later, pay-in-installments, and deferred payment options at checkout — integrated via hosted UI or headless API for e-commerce platforms.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Basic Auth with API key/secret is simple but requires careful secret management. PCI-DSS compliant — Klarna handles card data, not merchants. Webhook signatures should be validated. GDPR compliant.
⚡ Reliability
Best When
Your e-commerce platform wants to offer installment and deferred payment options, especially in EU markets where Klarna has strong brand recognition.
Avoid When
You need instant synchronous payment confirmation — Klarna's authorization is async and can be declined post-checkout.
Use Cases
- • Adding BNPL payment options to e-commerce checkout flows
- • Agents managing Klarna order lifecycle (create, capture, refund, cancel)
- • Fetching order status and payment details for customer service automation
- • Reconciling Klarna settlements with internal accounting systems
- • Triggering partial/full captures and refunds from order management systems
Not For
- • Direct peer-to-peer payments (consumer product, not API-first)
- • Markets where Klarna is not available (US coverage limited vs EU)
- • Real-time payment confirmations — Klarna uses asynchronous authorization
Interface
Authentication
HTTP Basic Auth with API Key (username) and API Secret (password). Separate credentials for Playground and Production environments. EU, NA, and OC regions have separate base URLs.
Pricing
Revenue-share model — Klarna charges merchants a percentage. No monthly API fee. Must sign merchant agreement to go live.
Agent Metadata
Known Gotchas
- ⚠ Authorization is asynchronous — order approved at checkout can later be declined; agents must handle webhook fraud callbacks
- ⚠ Region matters: EU (api.klarna.com), NA (api-na.klarna.com), OC (api-oc.klarna.com) — wrong region returns authentication errors
- ⚠ Order capture must happen within a time window (typically 28 days) or authorization expires silently
- ⚠ Partial captures allowed but partial refunds have product-specific rules — agents must check order type
- ⚠ Playground environment uses different credentials than production — test keys return 401 in production silently
Alternatives
Full Evaluation Report
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Scores are editorial opinions as of 2026-03-06.