Klaviyo vs Substack
Klaviyo and Substack are both email marketing software. Klaviyo is a commercial product from Klaviyo. Substack is a commercial product from Substack Inc.
Which to pick
- Pick Klaviyo when
- A Shopify or other online store wants purchase-driven email and SMS marketing.
- Pick Substack when
- A writer wants to start a free or paid newsletter at no upfront cost and benefit from Substack's discovery network.
Side by side
Email and SMS marketing for e-commerce, using store purchase data for segmentation, flows like abandoned cart, and revenue attribution.
Newsletter and blog platform with paid subscriptions, podcasts, video and a reader network and app.
Costs rise steeply with list size because billing counts active profiles.
It takes 10 percent of paid subscription revenue, and branding and design control are limited.
Production-ready (both)
Cloud service and mobile app (both)
Not published (both)
Closed source, sold by Klaviyo
Closed source, sold by Substack Inc.
Closed source: you use it under the maker's terms and cannot change or resell the code. (both)
839 Wikipedia readers a month on phones
25k Wikipedia readers a month on phones
Other comparisons
More email marketing and newsletter software
Both sides were judged on 2026-11-03 from makers' descriptions, Wikipedia, READMEs and GitHub data. License, age and popularity lines are worked out directly.