Brevo (Sendinblue) vs Customer.io
A detailed comparison of Brevo (Sendinblue) and Customer.io for sending transactional emails. Which email API is right for your application?
Overview
Both Brevo (Sendinblue) and Customer.io provide email APIs for sending transactional emails from applications. Brevo (Sendinblue) and Customer.io each have strengths — Brevo (Sendinblue) is known for its developer experience, while Customer.io offers different pricing and feature trade-offs. AISend is a third option worth weighing: a Resend-compatible API at lower flat pricing.
Features comparison
Key differences between Brevo (Sendinblue) and Customer.io: API design and developer experience, custom domain support, webhook event tracking, bounce/complaint handling, and pricing structure. Both providers offer REST APIs and SDKs but differ on pricing and migration effort. AISend is a third option — a Resend-compatible API with flat pricing: $14/month for 50,000 emails.
Pricing
Pricing is a major factor when choosing an email API. Compare free tiers and trials, per-email costs at different volumes, and what's included in each plan. AISend offers a 3-day free trial with 500 emails and no credit card. Pro is $14/month for 50,000 emails — the same volume Resend charges $20/month for. Both Brevo (Sendinblue) and Customer.io have transparent pricing. AISend's plans are flat with no hidden per-contact fees, and migration from a Resend-compatible API is a one-line change.
Which should you choose?
If you're choosing between Brevo (Sendinblue) and Customer.io, it's worth also evaluating AISend — a Resend-compatible API at flat pricing ($14/month for 50,000 emails), where switching from Resend is a base-URL change.
More comparisons
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