Documentation

Everything you need to schedule and deliver webhooks with SendItWhenever — from your first request to the full SDK and REST reference. This is the single source of truth; if anything here conflicts with older notes, trust this.

Introduction

Getting StartedWhat SendItWhenever is, how a schedule flows from creation to firing, and your first scheduled webhook in three lines.

Guides

AuthenticationAPI keys for machines, session login for humans, and which endpoints require which credential.SchedulingChoosing a fire time, payloads, custom methods and headers, idempotency, and Early Firing.Reliability & RetriesAt-least-once delivery, exponential backoff, the dead-letter queue, and inspecting delivery attempts.Verifying WebhooksThe X-SendIt-Signature header, verifying it on your endpoint, and zero-downtime secret rotation.Local Development & TunnelsWhy localhost can't be a target, and the tunnel pattern that lets you debug a scheduled webhook against your local machine.Security ModelSSRF protection, Encryption at Rest, and the abuse limits you may encounter.Plans & LimitsWhat each plan includes and exactly what happens when you hit a limit.

Reference

SDK ReferenceEvery method on the @sendithq/sdk client, with parameters and return types.REST API ReferenceEvery HTTP endpoint and the POST /v1/schedules request schema, for use without the SDK.Error CodesEvery error code, the HTTP status it maps to, and what to do about it.FAQ & TroubleshootingAnswers to the questions that come up most often when integrating.