Newsletter Sponsor Finder — Substack newsletters that take sponsors

Looking for newsletters to advertise in? Give this Actor a topic ("fintech", "AI", "marketing") or a Substack category, and it returns newsletters in that niche that actually run sponsors — with audience size, posting cadence, engagement and the brands that already sponsored them.

It reads each newsletter's recent posts and detects sponsor blocks ("Brought to you by…", "Sponsored by…", "Today's sponsor…"), so you only get newsletters with proven sponsorship activity.

Who it's for

• Brands & growth teams — build a media list of newsletters your audience reads, prioritized by size and sponsorship history.
• Agencies & media buyers — see which newsletters competitors sponsor and how often.
• Newsletter writers — find brands that sponsor newsletters like yours: warm leads for your own sponsorship sales.

Example

keywords: ["AI"], categories: ["Technology"], 15 newsletters (September 2026):

Newsletter	Subscribers	Sponsored posts	Recent sponsors
The Pragmatic Engineer	1,100,000	3 of 10	turbopuffer, Antithesis, Linear, WorkOS
Product Growth	241,000	5 of 10	Arize, Bolt, Product Faculty
Latent.Space	202,000	1 of 10	Supabase
Engineering Leadership	197,000	5 of 10	Unblocked, Hygraph, DX
Last Week in AI	184,000	5 of 10	ODSC, Langfuse
Ben's Bites	171,000	1 of 10	Google Cloud
Elena's Growth Scoop	99,000	4 of 10	Firecrawl, Chargebee, Optimizely, Amplitude

The run took about 2 minutes and scanned 116 newsletters to find 15 with sponsors.

Input

{
  "keywords": ["fintech", "payments"],
  "categories": ["Finance"],
  "maxNewsletters": 30,
  "onlyWithSponsors": true,
  "minSubscribers": 1000,
  "postsPerNewsletter": 10,
  "language": "en"
}

• keywords search Substack for newsletters writing about each topic.
• categories browse Substack's own categories (Technology, Business, Finance, Crypto, Health & Wellness…), most popular first.
• onlyWithSponsors (default on) returns only newsletters with at least one sponsored post among those scanned. Turn it off to get every newsletter in the niche with its stats.

Output

One row per newsletter:

{
  "name": "Elena's Growth Scoop",
  "url": "https://www.elenaverna.com",
  "author": "Elena Verna",
  "authorProfileUrl": "https://substack.com/@plgrowth",
  "subscribers": 99000,
  "subscribersLabel": "Tens of thousands of subscribers",
  "paidSubscriptions": true,
  "postsScanned": 10,
  "sponsoredPosts": 4,
  "sponsoredShare": 0.4,
  "sponsors": [
    {
      "name": "Firecrawl",
      "domain": "firecrawl.dev",
      "posts": 2
    },
    {
      "name": "Chargebee",
      "domain": "chargebee.com",
      "posts": 1
    }
  ],
  "lastSponsoredPostDate": "2026-09-24T17:58:00.785Z",
  "postsPerMonth": 2.4,
  "avgReactions": 354,
  "avgComments": 29
}

The SUMMARY record adds a sponsor leaderboard: every brand found, ranked by how many newsletters in your niche it sponsors. It's a quick map of who buys newsletter ads in that market.

Pricing

$0.02 per newsletter returned. Newsletters scanned but filtered out (no sponsors, too small) are not charged. Set a maximum cost per run and the Actor stops before exceeding it.

Good to know

• Coverage: Substack newsletters only, including those on custom domains. Newsletters on beehiiv, Ghost or ConvertKit aren't included.
• Detection: sponsor blocks with a link are detected reliably. Sponsors mentioned only in plain text can be missed, and occasionally a cross-promotion with another newsletter is counted as a sponsor.
• Niche size: in smaller niches only a fraction of newsletters run sponsors, so the Actor may return fewer than maxNewsletters after scanning up to 10× that many.
• Subscriber counts are the public figures Substack shows; some newsletters hide theirs.
• No contact emails are returned. Use the newsletter URL or the author's Substack profile to reach out.

Need post-level data for specific newsletters instead? See Substack Scraper & Newsletter Sponsor Finder.