Reletter
Reletter API

Search Filters

Both the publication search and the issue search endpoints accept an optional filters query parameter, which is a comma-separated list of filters in the form name:operator:value. This page is part of the Reletter API documentation.

Example
GET /api/search/publications/?query=climate&filters=active:is:true,subscribers:gte:5000,languages:any:en
  • The same filters apply to /api/search/publications/ and /api/search/issues/.
  • Filters combine with AND logic.
  • Maximum 20 filters per request.
  • Multi-value filters use a hyphen-separated list, e.g. languages:any:en-es-fr (max 25 values).

Subscribers

Newsletters with at least 5,000 subscribers: subscribers:gte:5000

Newsletters with at most 250,000 subscribers: subscribers:lte:250000

Engagement

Engagement score of at least 75: engagement:gte:75

Engagement score of at most 45: engagement:lte:45

Monthly visits

At least 10,000 estimated monthly site visits: monthlyvisits:gte:10000

At most 1,000,000 estimated monthly site visits: monthlyvisits:lte:1000000

Number of issues

Newsletters that have published at least 100 issues: issues:gte:100

Newsletters that have published at most 10 issues: issues:lte:10

Founded

Founded on or after 2022-01-01 (Unix time in seconds): founded:gte:1640995200

Founded between 2022-01-01 and 2024-01-01: founded:gte:1640995200,founded:lte:1704067200

Active

Newsletters that have published an issue recently: active:is:true

Inactive (dormant) newsletters: active:is:false

Sponsored

Newsletters that accept sponsorships or advertisers: sponsored:is:true

Languages

Refer to /api/misc/languages/ for the full list of supported language codes.

English newsletters: languages:any:en

English, Spanish or French newsletters: languages:any:en-es-fr

Platforms

  • substack
  • linkedin_newsletter
  • ghost
  • beehiiv
  • kit

Substack newsletters only: platforms:any:substack

Substack, Beehiiv or Kit newsletters: platforms:any:substack-beehiiv-kit

Publishing model

  • free — fully free
  • freemium — free with a paid tier
  • paid — paid subscription required

Free or freemium newsletters: pubmodels:any:free-freemium

Frequency

  • daily
  • twiceweekly
  • weekly
  • monthly
  • infrequently

Newsletters that publish daily: frequencies:any:daily

Newsletters that publish daily or weekly: frequencies:any:daily-weekly

Sort

Pass a single sort:eq:<value> filter to control result ordering. Allowed values:

  • subscribers_relevance — default for publication search; balances relevance and subscriber count
  • subscribers — most subscribers first
  • monthly_visits — most estimated monthly visits first
  • engagement — highest engagement first
  • issues — most issues published first
  • newest — newest first (default for issue search with an empty query)
  • oldest — oldest first

Sort by subscribers, descending: sort:eq:subscribers