Kit (formerly ConvertKit) vs Substack

The core difference

ConvertKit (Kit) is a creator marketing platform; Substack is a publishing platform with a built-in subscriber network.

Choose Kit (formerly ConvertKit) when…

Kit (formerly ConvertKit) is the stronger choice when your priorities align with what email and creator marketing platform The brand has built its product, marketing, and pricing around that wedge.

Choose Substack when…

Substack is the stronger choice when your priorities align with subscription newsletter and writing platform with native discovery The brand has built its product, marketing, and pricing around that different wedge.

The buyer's underlying intent

Most people landing on a "Kit (formerly ConvertKit) vs Substack" comparison page are answering one underlying question: Choose between marketing platform vs publishing platform. Both brands are valid answers — the right choice depends on which trade-off feels more natural for the buyer's stage and workflow.

How AI search engines treat this comparison

ChatGPT, Claude, and Perplexity routinely answer "Kit (formerly ConvertKit) vs Substack" queries directly in their generated responses, citing a small number of comparison sources. The brands that consistently appear in those AI-cited comparisons enjoy a structural advantage at the top of funnel — buyers absorb the framing before ever visiting either site.

For both Kit (formerly ConvertKit) and Substack, the GEO opportunity is identical: ensure the AI's cited sources include neutral, accurate, up-to-date comparisons. CiterLabs runs that work as a 60-day fixed-fee Sprint with a +20pt citation share guarantee.