Substack on your landing pages
Substack is a great place to publish and a hard place to run paid acquisition. Your publication page isn't yours to split test, and Substack doesn't offer an API for adding subscribers, so no page builder can push readers into your list behind the scenes. We'd rather say that plainly than sell you a connector that doesn't exist.
What LanderLab does is give you the page Substack doesn't: a signup page or quiz on your own domain, with A/B tests, your pixel firing on the lead, and the UTMs and variant saved with every reader. Readers then move into Substack the two ways Substack supports: Substack's own embed form, placed on the page in a Custom Code element, or an import of the readers from LanderLab's Leads tab as a CSV (export is on Grow and up).
It's for writers and media buyers who want to grow a Substack with Meta, TikTok or native ads and still know their cost per reader by ad set and by page.
Why paid traffic needs a page in front of your Substack
Your Substack page is written for readers who already know you. A cold click from an ad needs something else: a headline that matches the ad, a clear promise, proof, and one obvious action. On LanderLab you build that page on your own domain and test it like any other paid funnel.
You also get measurement built for advertisers. The signup fires your pixel, the variant is recorded, and the click's UTMs are saved with the reader, so the ad platform optimizes for signups and you see which campaigns pay for themselves.
Importing paid readers into Substack
Because Substack has no API for adding subscribers, the reliable bridge is Substack's own import. Readers collect in the page's Leads tab with their answers and campaign, and a CSV export of them, on Grow and up, goes into Substack's import, which skips invalid and duplicate emails and asks you to confirm everyone opted in. So the page should say plainly that the reader is subscribing to your newsletter.
The trade-off is timing: it's a batch, not a live push. Run it on a schedule, daily while a campaign is live, and new readers get your next issue on time.
When to use Substack's embed form instead
Substack gives every publication an embeddable signup form, and it can sit in a Custom Code element on a LanderLab page, inside your own headline and proof. The reader subscribes in Substack's form, live, with nothing to import.
What you give up is attribution. The signup happens inside Substack's frame, so LanderLab doesn't record it as a lead, your UTMs don't reach Substack, and the page can't count the signup as its conversion. It's the right call for a fast angle test, and the import route is the right call for scaling spend.
Know what each Substack reader cost
With the import route, every reader in your export carries the campaign and the A/B variant that produced them. Put spend next to the counts and you have cost per reader by ad set and by page version, the number that decides where the next dollar goes. Tag each import by campaign in Substack and you can find those readers by tag later.
