Retrieve newsletter audience overlap data via API
Edit in CMSOverview
Section titled “Overview”The Letterhead API provides endpoints to analyze how much your newsletters’ audiences overlap. This helps you understand subscriber relationships across your publications and measure your combined reach. This data is available over the API only.
What you can retrieve
Section titled “What you can retrieve”The API provides two types of overlap data:
Pairwise overlap for all newsletters — see Get audience overlap across all newsletters:
- How many active subscribers each pair of newsletters shares
- Each newsletter’s own active-subscriber total
- Complete view across your entire portfolio
Detailed breakdown for newsletters you choose — see Compare audience overlap for selected newsletters:
- Combined unique reach across the whole selection
- Each newsletter’s own total, and how many subscribers are exclusive to it
- The shared count for every overlapping group within your selection — each pair, each trio, and so on, not just the people on all of them
Pick between two and five newsletters, each one distinct. Counts are active subscribers only, and people are counted once even if they’re on several of your newsletters.
Use cases
Section titled “Use cases”This data helps you:
- Identify which newsletters share the most subscribers
- Calculate your true unique reach across multiple publications
- Make informed decisions about cross-promotion opportunities
- Understand audience segmentation across your portfolio
Next steps
Section titled “Next steps”- API reference — full paths, parameters, and response formats
- Generate & manage API keys
- Using the Letterhead API
Still can’t find what you need? Contact support.