Substack
Hosted newsletter platform with social network features.
Substack is closed and opinionated: 10% revenue cut, no API, no custom domains for free, but distribution and recommendations are real. Largely outside the developer toolchain conversation.
Judged purely as an API. What the request contract guarantees on retry, how complete the webhook event coverage is, whether suppressions are readable and writable programmatically, and how much the message log retains when something needs debugging in production.
Against high-frequency programmatic sends where a missed delivery is a product failure, Substack covers the suppressions API and batch sending, and does not cover idempotency keys, webhook coverage, event stream, operating track record, and SDK breadth. Whether that gap matters depends on how central those are to the build.
- Idempotency keys: No
- Webhooks: No
- Event stream: No
- Operating since: 2017
- Suppressions API: Yes
- Best published rate per 1,000: Tiers not published in comparable form
- Batch sending: Yes
- SDKs: None
- Deliverability: Reasonable for content-driven newsletters.
Reasonable for content-driven newsletters.
Writers who prioritize distribution over flexibility.
- › Distribution via the Substack network
- › No platform fees beyond revenue cut
- › No API, no automation, no custom domain on free
- › Lock-in to platform
Features at a glance
| API | No |
| SMTP | No |
| SDKs | None |
| Webhooks | No |
| Templates | basic |
| React Email | No |
| Batch send | Yes |
| Scheduled send | Yes |
| Suppressions | Yes |
| Multi-tenant | No |
| Inbound parsing | No |
| Event stream | No |
| Idempotency keys | No |
| Dedicated IP | No |