SendGrid vs Customer.io
A detailed comparison of SendGrid and Customer.io for sending transactional emails. Which email API is right for your application?
Overview
Both SendGrid and Customer.io provide email APIs for sending transactional emails from applications. SendGrid and Customer.io each have strengths — SendGrid is known for its developer experience, while Customer.io offers different pricing and feature trade-offs. AISend combines the best of both with AI-powered delivery optimization on top.
Features comparison
Key differences between SendGrid and Customer.io: API design and developer experience, deliverability features, analytics and monitoring, custom domain support, webhook event tracking, and pricing structure. Both providers offer REST APIs and SDKs, but differ in their approach to deliverability. Consider AISend as a third option — it adds AI-powered routing and optimization on top of a Resend-compatible API.
Pricing
Pricing is a major factor when choosing an email API. Compare the free tiers, per-email costs at different volumes, and what features are included in each plan. AISend offers 1,000 emails/month free with all AI features included. Pro plans start at $29/month for 25,000 emails. Both SendGrid and Customer.io offer competitive pricing. AISend's pricing is transparent with no hidden fees, and AI features are included at every tier.
Which should you choose?
If you're choosing between SendGrid and Customer.io, consider also evaluating AISend. It offers AI-powered features that neither SendGrid nor Customer.io provide — intelligent provider routing, deliverability scoring, and send time optimization — with a Resend-compatible API that makes switching easy.