Email APIs · side by side
Customer.io vs Klaviyo
Compare Customer.io, Klaviyo by sending volume, delivery webhooks, inbound email, domain limits and retention.
Email APIs pricing calculator
25K
Customer.io
Custom / not listed
Custom / unlisted usage pricing · 25K profiles
Klaviyo
Custom / not listed
Custom / unlisted usage pricing · 25K profiles
Listed USD plan fees and tracked usage only. Unlisted compute, transfer, extras, taxes and contract terms are excluded. Custom or unsupported plan usage is not estimated.
Email APIs overview & pricing
| Email APIs | Customer.io | Klaviyo |
|---|---|---|
| Provider | Customer.io | Klaviyo |
| Billing unit | profiles | profiles |
| Plan at selected usage | Custom / unlisted usage pricing | Custom / unlisted usage pricing |
| Monthly estimate | Custom / not listed | Custom / not listed |
| Workload | 25K profiles | 25K profiles |
| Free access | Trial | Limited free plan |
| Published plans | Essentials, Premium, Enterprise | Free |
| Prices checked | 2026-10-08 | 2026-10-08 |
Provider
- Customer.io
- Customer.io
- Klaviyo
- Klaviyo
Billing unit
- Customer.io
- profiles
- Klaviyo
- profiles
Plan at selected usage
- Customer.io
- Custom / unlisted usage pricing
- Klaviyo
- Custom / unlisted usage pricing
Monthly estimate
- Customer.io
- Custom / not listed
- Klaviyo
- Custom / not listed
Workload
- Customer.io
- 25K profiles
- Klaviyo
- 25K profiles
Free access
- Customer.io
- Trial
- Klaviyo
- Limited free plan
Published plans
- Customer.io
- Essentials, Premium, Enterprise
- Klaviyo
- Free
Prices checked
- Customer.io
- 2026-10-08
- Klaviyo
- 2026-10-08
Email APIs monthly cost
Customer.io: Not pricedKlaviyo: Not priced
Cost by profiles
Cost curve data
| profiles | Customer.io | Klaviyo |
|---|---|---|
| 0 | $100 | $0 |
| 6,250 | Not priced | Not priced |
| 12.5K | Not priced | Not priced |
| 25K | Not priced | Not priced |
| 50K | Not priced | Not priced |
| 125K | Not priced | Not priced |
| 250K | Not priced | Not priced |
0
- Customer.io
- $100
- Klaviyo
- $0
6,250
- Customer.io
- Not priced
- Klaviyo
- Not priced
12.5K
- Customer.io
- Not priced
- Klaviyo
- Not priced
25K
- Customer.io
- Not priced
- Klaviyo
- Not priced
50K
- Customer.io
- Not priced
- Klaviyo
- Not priced
125K
- Customer.io
- Not priced
- Klaviyo
- Not priced
250K
- Customer.io
- Not priced
- Klaviyo
- Not priced
Which email providers fit your needs?
Customer.io features & plan notes
- Behavioral messaging
- Lifecycle workflows
- Event triggers
Klaviyo features & plan notes
- E-commerce data
- Omnichannel
- Shopify ecosystem
How to compare email providers
Separate transactional delivery from campaigns, outreach and agent inboxes. Compare monthly sends and daily caps; contacts, seats and inboxes are not sending allowances. Budget separately for dedicated IPs, validation and attachments.
Browse Email APIs pricing