useSend SDK

Prerequisites

- useSend API key
- Verified domain

Installation

$3

``bash
npm install usesend
`

$3

`bash
yarn add usesend
`

$3

`bash
pnpm add usesend
`

$3

`bash
bun add usesend
`

Usage

`javascript
import { UseSend } from "usesend";

const usesend = new UseSend("us_12345");

// for self-hosted installations you can pass your base URL
// const usesend = new UseSend("us_12345", "https://app.usesend.com");

usesend.emails.send({
to: "hello@acme.com",
from: "hello@company.com",
subject: "useSend email",
html: "

useSend is the best open source product to send emails

",
text: "useSend is the best open source product to send emails",
});

// Safely retry sends with an idempotency key
await usesend.emails.send(
{
to: "hello@acme.com",
from: "hello@company.com",
subject: "useSend email",
html: "

useSend is the best open source product to send emails

",
},
{ idempotencyKey: "signup-123" },
);

// Works for bulk sends too
await usesend.emails.batch(
[
{
to: "a@example.com",
from: "hello@company.com",
subject: "Welcome",
html: "

Hello A

",
},
{
to: "b@example.com",
from: "hello@company.com",
subject: "Welcome",
html: "

Hello B

",
},
],
{ idempotencyKey: "bulk-welcome-1" },
);
// Reusing the same key with a different payload returns HTTP 409.
`

Campaigns

Create and manage email campaigns:

`javascript
import { UseSend } from "usesend";

const usesend = new UseSend("us_12345");

// Create a campaign
const campaign = await usesend.campaigns.create({
name: "Welcome Series",
from: "hello@company.com",
subject: "Welcome to our platform!",
contactBookId: "cb_12345",
html: "

Welcome!

Thanks for joining us.

",
sendNow: false,
});

// Schedule a campaign
await usesend.campaigns.schedule(campaign.data.id, {
scheduledAt: "2024-12-01T09:00:00Z",
batchSize: 1000,
});

// Get campaign details
const details = await usesend.campaigns.get(campaign.data.id);

// Pause a campaign
await usesend.campaigns.pause(campaign.data.id);

// Resume a campaign
await usesend.campaigns.resume(campaign.data.id);
`

Webhooks

Verify webhook signatures and get typed events:

`ts
import { UseSend } from "usesend";

const usesend = new UseSend("us_12345");
const webhooks = usesend.webhooks(process.env.USESEND_WEBHOOK_SECRET!);

// In a Next.js App Route
export async function POST(request: Request) {
try {
const rawBody = await request.text(); // important: raw body, not parsed JSON
const event = webhooks.constructEvent(rawBody, {
headers: request.headers,
});

if (event.type === "email.delivered") {
// event.data is strongly typed here
}

return new Response("ok");
} catch (error) {
return new Response((error as Error).message, { status: 400 });
}
}
`

You can also use the Webhooks class directly:

`ts
import { Webhooks } from "usesend";

const webhooks = new Webhooks(process.env.USESEND_WEBHOOK_SECRET!);
const event = webhooks.constructEvent(rawBody, { headers: request.headers });
`

Need only signature verification? Use the verify method:

`ts
const isValid = webhooks.verify(rawBody, { headers: request.headers });

if (!isValid) {
return new Response("Invalid signature", { status: 401 });
}
`

Express example (ensure raw body is preserved):

`ts
import express from "express";
import { Webhooks } from "usesend";

const webhooks = new Webhooks(process.env.USESEND_WEBHOOK_SECRET!);

const app = express();
app.post("/webhook", express.raw({ type: "application/json" }), (req, res) => {
try {
const event = webhooks.constructEvent(req.body, {
headers: req.headers,
});

if (event.type === "email.bounced") {
// handle bounce
}

res.status(200).send("ok");
} catch (error) {
res.status(400).send((error as Error).message);
}
});
`

Headers sent by UseSend:

- X-UseSend-Signature: v1= + HMAC-SHA256 of ${timestamp}.${rawBody}
- X-UseSend-Timestamp: Unix epoch in milliseconds
- X-UseSend-Event: webhook event type
- X-UseSend-Call: unique webhook attempt id

By default, signatures are only accepted within 5 minutes of the timestamp. Override with toleranceMs` if needed.