Communications APIs that just work.
Send SMS, place voice calls, deliver transactional email, and reach customers on WhatsApp — all from a single, developer-first API. Generate a key and ship your first message in minutes.
No credit card required. Free tier includes 100 messages / month.
curl https://relay.dev/api/v1/messages \
-H "Authorization: Bearer sk_live_..." \
-H "Content-Type: application/json" \
-d '{
"channel": "sms",
"to": "+14155550123",
"from": "Relay",
"body": "Your code is 224466"
}'Every channel, one integration
Swap the channel field and reuse the same request shape across all four channels.
SMS
Send and receive text messages worldwide with delivery tracking and segment counting.
POST /api/v1/messagesVoice
Place programmable phone calls with text-to-speech and call status callbacks.
POST /api/v1/callsDeliver transactional email with high inbox placement and open tracking.
POST /api/v1/emailMessage customers on WhatsApp using approved templates and rich media.
POST /api/v1/whatsappAPI keys in one click
Generate, name, and revoke scoped keys from your dashboard. Keys are hashed and shown only once.
Usage & logs built in
Every request is logged with status, latency, and cost. Filter by channel and export anytime.
From zero to first message in three steps
Create an account
Sign up with your email. No credit card, no sales call.
Generate an API key
Create a scoped key from your dashboard. Copy it once and store it securely.
Send your first message
Call the API with your key. Watch it appear in your logs in real time.