Lob Print & Mail API

Start with a test postcard

The official quickstart requires a Lob account and an API key, and recommends exploring the API with the test environment before moving to live use. It shows installing a client library for a supported language, then building a postcard request with recipient and sender address fields and front and back artwork URLs. The SDK calls the postcard creation operation and returns the API response. Those instructions are illustrative documentation; no postcard was created or mailed for this listing.

This workflow suits software that needs to trigger a physical follow-up from a customer or operational event. Lob's product page describes sending mail from a CRM or customer data system and lists formats beyond postcards, including letters, checks, snap packs, self-mailers, and booklets. Review the format-specific API reference and template requirements before preparing production artwork. Address verification is offered as a separate API capability, not a prerequisite established here.

Budget for the physical piece

The Developer plan has no monthly platform fee, but it does not make printed mail free: Lob charges for print and postage per piece. Higher tiers add platform fees and different usage allowances or mail rates. The pricing page says rates vary by format and plan, so estimate the actual mix of mail types and destinations before choosing a tier.

The API uses account credentials and supports distinct test and live keys. Keep secret keys on a server rather than exposing them in a browser or mobile app; the docs describe publishable keys as limited to address verification and autocomplete requests. That distinction matters because a mail-creation integration needs the appropriate secret credential and a deliberate transition from test to live traffic.