AudienceFlow - Content Retention Analytics for Creators (Substack, Ghost, YouTube)

Track how many of your newsletter/video subscribers drop off each day after each piece of content. Predict which content format keeps audience longest and which loses them fastest.

𝕏 Post Reddit HN

Difficulty

intermediate

What is it?

Creators know their subscriber count but not *why* people leave. A newsletter creator sends 2 articles per week but doesn't know if issue #42 (political take) lost 500 subscribers in 48 hours or if it was something else. YouTube creators see subscriber count fluctuate but have no early warning system for content drift. AudienceFlow connects to Substack, Ghost, YouTube, or Patreon via API, ingests subscriber/viewer data daily, and shows retention curves: 'After this article, audience dropped 3% in 24h, recovered to flat in 7 days.' It detects patterns: 'Videos about X format lose subscribers fastest. Articles about Y retain best.' Creators use this to adjust content strategy before large audience erosion happens. This solves a real problem: analytics are reactive (you see the damage after 2 weeks). AudienceFlow is predictive (you see the signal within 24-48h). Why 100% buildable right now: Substack API, YouTube Analytics API, and Ghost API all exist and are accessible. Daily data collection and simple retention math (curve fitting) are straightforward. Supabase + Next.js handles dashboards. No custom ML—just percentile aggregation.

Why now?

Creator economy is booming—Substack passed 1 million writers in late 2025. YouTube Shorts growth means more channels hitting 10k threshold. Creators are asking 'how do I keep my audience?' on Twitter/X daily.

▸Daily subscriber/viewer ingestion from Substack/YouTube/Ghost/Patreon APIs (Implementation: scheduled job pulling data each day, store deltas in Postgres)
▸Retention curve visualization per content piece (Implementation: Recharts, compute % retained at 1d, 7d, 30d post-publish)
▸Content format performance comparison (Implementation: tag content by format, aggregate retention by tag, show bar chart)
▸Churn prediction alerts (Implementation: if daily churn exceeds threshold, send Slack notification within 24h)

Target Audience

Newsletter creators (Substack, Ghost) and YouTubers with 10k+ subscribers. ~50,000 active Substack creators, ~30,000 YouTube channels hitting 10k subs monthly.

Example Use Case

Jamie runs a Substack with 25k subscribers. She writes 2 newsletters per week but doesn't know which topics keep people subscribed. She uses AudienceFlow: sees that articles about 'AI tools' lose 2% subscribers in 48h, but articles about 'remote work trends' retain 99.5% through week 1. She adjusts her content mix, increases retention by 8%, and grows to 35k subscribers in 3 months. She upgrades to Premium for YouTube and Patreon integration.

User Stories

▸As a Substack creator with 20k subscribers, I want to see how many people unsubscribe within 48 hours of each article, so that I can avoid topics that cause churn.
▸As a YouTuber, I want early warning if a video format is losing subscribers faster than normal, so that I can adjust before major audience loss.
▸As a creator, I want to compare retention across different content formats (e.g., 'personal essay' vs 'tool review'), so that I can focus on what keeps my audience engaged.

Acceptance Criteria

Substack sync: done when daily subscriber data syncs and is accurate within 100 subscribers. Retention curve: done when retention % at 1d, 7d, 30d match manual calculation. Churn alert: done when alert fires within 1 hour of churn exceeding threshold. Dashboard: done when charts render in under 2s with month of data.

Is it worth building?

$9/month × 150 creators = $1,350 MRR at month 2. $39/month × 120 creators = $4,680 MRR at month 4.

Unit Economics

CAC: $4 (organic ProductHunt + Twitter). LTV: $108 (12 months at $9/month). Payback: 3 months. Gross margin: 85% (minimal API costs).

Business Model

SaaS subscription by creator tier (subscribers).

Monetization Path

Free tier: basic retention curves, 30-day history. Pro: $9/month, retention predictions, content format analysis, Slack alerts. Premium: $39/month, multi-platform (YouTube + Substack), cohort analysis, content recommendation API.

Revenue Timeline

First dollar: week 2 (via ProductHunt early access). $1k MRR: month 3. $5k MRR: month 6. $10k MRR: month 10.

Estimated Monthly Cost

YouTube API: free. Substack data: free (no official API cost). Ghost API: free. Stripe fees: $10 at $1.3k MRR. Vercel: $20. Supabase: $25. Total: ~$55/month at launch.

Profit Potential

Full-time viable at $3k–$12k MRR.

Scalability

High — can expand to TikTok, Discord, Twitter/X communities, support advisor recommendations, sponsor matching based on audience retention patterns.

Success Metrics

Week 2: 80 beta signups. Week 3: 25 free-to-paid conversions. Month 2: 50 paying creators. 70% of paid users view dashboard weekly.

Launch & Validation Plan

Survey 40 active Substack and YouTube creators on Twitter/X and creator Discord communities. Build landing page with retention curve examples. Recruit 5 creators for beta (offer free Pro for 3 months). Validate that 75% of creators can connect Substack and see accurate retention data within 24h.

Customer Acquisition Strategy

First customer: DM 20 mid-tier creators on Twitter/X offering free 3-month trial in exchange for feedback. Then: ProductHunt, creator-focused subreddits (r/Substack, r/YouTubers), Substack newsletter directories, Twitter thread with retention curve examples, indie hacker communities.

What's the competition?

Competition Level

Low

What's the roadmap?

Feature Roadmap

V1 (launch): Substack/YouTube data sync, retention curves, format comparison. V2 (month 2): churn predictions, Slack alerts, multi-platform dashboards. V3 (month 4): content recommendation engine, sponsor matching, cohort analysis by subscriber source.

Milestone Plan

Phase 1 (Week 1-2): Substack OAuth + daily sync + retention curve calculation. Done when test creator sees accurate retention data. Phase 2 (Week 3-4): dashboard UI + YouTube integration + Stripe checkout. Done when 5 creators can pay and see multi-platform dashboard. Phase 3 (Month 2): format analysis + churn alerts + Slack integration. Done when creator receives churn alert within 1 hour of event.

How do you build it?

Tech Stack

Next.js, YouTube Analytics API, Substack API, Ghost API, Supabase, Stripe — build with Cursor for API sync jobs, Lovable for dashboard, v0 for retention curve charts.

Time to Ship

3 weeks

Required Skills

YouTube Analytics API, Substack API parsing, SQL time-series queries, Stripe billing.

Resources

YouTube Analytics API docs, Substack API (reverse-engineered), Ghost API docs, Stripe docs.

MVP Scope

Landing page (Lovable), Substack OAuth + data sync (Cursor), YouTube OAuth + data sync (Cursor), retention curve dashboard (v0 + Recharts), Stripe checkout. Core files: /pages/api/auth/substack.ts, /pages/api/sync/substack.ts, /pages/dashboard.tsx, /components/RetentionCurve.tsx.

Core User Journey

Sign up -> connect Substack -> wait 24h for first data sync -> see retention curve for latest article -> identify low-retention content type -> upgrade to Pro.

Architecture Pattern

User OAuth -> Substack/YouTube API daily job -> store subscriber deltas in Postgres -> calculate retention curves -> Supabase real-time emits updates -> dashboard polls for new data -> display retention chart.

Data Model

Creator has many Pieces (articles/videos). Piece has many DailyMetrics. DailyMetric includes subscriber_count, churn_count, retention_percent. Creator has one ContentStrategy (tags for format analysis).

Integration Points

Substack API for subscriber data, YouTube Analytics API for watch time and subscribers, Ghost API for email metrics, Stripe for subscription, Slack for churn alerts, Resend for email reports.

V1 Scope Boundaries

V1 excludes: TikTok/Discord/Twitter integration, AI content recommendations, cohort analysis, white-label, API access for third-party apps.

Success Definition

A creator connects Substack, reviews retention curves for past 4 weeks, identifies one content format that loses subscribers, and adjusts strategy based on data.

Challenges

API access varies—Substack is unofficial API (terms risk), YouTube requires revenue-eligible channels, Ghost is self-hosted variant. Different platforms report differently (Substack subscribers vs YouTube views vs Watch Time). Retention curves need 30+ days of data to become reliable.

Avoid These Pitfalls

Do not assume linear retention (retention curves are exponential—need log scale chart). Do not compare retention across platforms (YouTube watch time != Substack opens). Do not alert on single day of churn (noise is high, need 3-day moving average).

Security Requirements

Auth: OAuth tokens (Substack, YouTube) stored encrypted. RLS on all creator data tables. Rate limiting: 30 req/min per creator. No PII stored (aggregate counts only). GDPR: data deletion endpoint, consent for analytics.

Infrastructure Plan

Hosting: Vercel (Next.js). Database: Supabase Postgres. Scheduled jobs: Vercel Cron or external job runner (e.g., EasyCron). CI/CD: GitHub Actions. Monitoring: Sentry for errors, custom dashboard for sync failures.

Performance Targets

Expected load: 100 DAU at launch. Daily sync: under 30 seconds for 100 pieces. Dashboard load: under 2s. Real-time retention updates: within 5 minutes of data ingestion.

Go-Live Checklist

☐Substack API: tested with 5 test accounts, OAuth flow verified
☐YouTube API: confirmed revenue-eligible access, quota limits documented
☐Retention math: validated against manual calculations
☐Stripe: full payment flow tested
☐Error handling: Sentry live
☐Monitoring: sync job failure alerts
☐Domain: AudienceFlow.com with SSL
☐Privacy: GDPR policy, aggregate-data-only commitment
☐Terms: published
☐Beta: 5 creators signed off
☐Rollback: manual data export
☐Launch: ProductHunt post with 'hidden churn' angle, Twitter thread with real creator retention curves.

How to build it, step by step

1. Create Next.js app. 2. Set up Supabase with tables: creators, pieces, daily_metrics. 3. Build Substack OAuth at /pages/api/auth/substack.ts. 4. Build YouTube OAuth at /pages/api/auth/youtube.ts. 5. Create scheduled sync job /pages/api/sync/substack.ts using node-cron. 6. Build retention curve calculation in /lib/retentionMath.ts. 7. Create dashboard at /pages/dashboard.tsx with Recharts. 8. Add Stripe checkout at /pages/api/stripe/checkout.ts. 9. Test: connect Substack, wait 24h, verify retention curves appear. 10. Deploy to Vercel.

Generated

March 23, 2026

Model

claude-haiku-4-5-20251001

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