Email, SMS & Messaging APIs
Send transactional email, text messages and chat notifications. 10 listed: 3 completely free, 0 usable without an API key.
Twilio
SMS, voice, WhatsApp and verification APIs.
SendGrid
Transactional and marketing email delivery from Twilio.
Resend
Developer-first email API with React Email support.
Postmark
Transactional email focused on fast, reliable inbox delivery.
Mailgun
Email sending, receiving and validation APIs.
Brevo API
Transactional email, SMS and marketing contacts with a generous free plan.
Vonage APIs
SMS, voice, video and verification APIs.
Slack Web API
Post messages, build bots and automate Slack workspaces.
Discord API
Bots, slash commands and webhooks for Discord communities.
Telegram Bot API
HTTP interface for building Telegram bots.
Comparing email, sms & messaging APIs
| API | Auth | Pricing model | Docs |
|---|---|---|---|
| Twilio | API key | Paid | twilio.com |
| SendGrid | API key | Free tier | twilio.com |
| Resend | API key | Free tier | resend.com |
| Postmark | API key | Free tier | postmarkapp.com |
| Mailgun | API key | Free tier | documentation.mailgun.com |
| Brevo API | API key | Free tier | developers.brevo.com |
| Vonage APIs | API key | Paid | developer.vonage.com |
| Slack Web API | OAuth | Free | api.slack.com |
| Discord API | OAuth | Free | discord.com |
| Telegram Bot API | API key | Free | core.telegram.org |
Not sure which to pick? Read our 12-point API checklist and guide to API pricing models.