REST API
A newsletter data API for your own stack
Search newsletters, articles and entities, read publication profiles and their sponsor history, and page through results with stable ids. Authenticate with an API key; every paid plan includes API access.
7 days of Pro, no credit card required
What it does
Search and profiles
Newsletters, articles and entities by query; full publication profiles by id or slug.
Entities as first-class records
Companies, products, people, guests, technologies, topics, brands and sponsors.
Documented and typed
OpenAPI 3.1, a Markdown reference and curl examples for every endpoint.
Clear limits
Monthly API quotas per plan and a per-minute rate limit per key.
Example
Example request
Abridged. The reference lists every endpoint and field.
curl "https://newsletterfit.com/api/v1/search?q=ai%20agents" \
-H "Authorization: Bearer nf_live_YOUR_KEY"{
"success": true,
"data": {
"query": "ai agents",
"newsletters": [
{
"id": 42,
"self": "/api/v1/publications/42",
"name": "The Ops Ledger",
"audience": { "value": 64000, "label": "64K", "basis": "substack" }
}
]
},
"meta": { "page": 1, "limit": 20, "total": 3 }
}FAQ
Do I need a separate plan for the API?
No. Pro, Intelligence and Enterprise all include API and MCP access, with quotas that grow by plan.
Is full article text included?
No. The API returns metadata, summaries, entities and links, not full article text or raw files.