---
title: Third-Party Auth Providers with Free Tiers (December 2025)
type: note
permalink: strategy/third-party-auth-providers-with-free-tiers-december-2025-1
tags:
- '[''authentication'''
- '''auth-providers'''
- '''comparison'''
- '''strategy'''
- '''decision'']'
---

# Third-Party Auth Providers with Free Tiers (December 2025)

## Comparison for Kinemotion (Vercel + Cloud Run)

| Provider | Free Tier | Vercel Integration | Backend Support | Best For |
|----------|-----------|-------------------|----------------|----------|
| **Clerk** | 10,000 MAUs | ⭐ Native | ✅ Excellent | **MVP Speed** |
| **Supabase** | 50,000 MAUs | ✅ Good | ✅ Excellent | **Long-term Cost** |
| **Auth0** | 25,000 MAUs | ✅ Good | ✅ Excellent | Enterprise features |
| **Firebase** | 50,000 MAUs* | ✅ Good | ✅ Good | Google ecosystem |

*Firebase free tier: email/password/social only. Phone auth costs extra.

---

## 1. Clerk (RECOMMENDED FOR MVP)

### Free Tier (December 2025)
- **10,000 MAUs** per month
- All authentication methods
- Pre-built UI components
- Custom domain
- Social logins (unlimited connections)
- Basic organizations (5 free)

### Paid Plans
- **Pro**: $25/month base + $0.02 per MAU over 10K
  - Example: 15,000 MAUs = $25 + (5,000 × $0.02) = $125/month

### Why Choose Clerk for Kinemotion
✅ **Native Vercel integration** (1-click install from marketplace)
✅ **Fastest setup** (5-10 minutes to production)
✅ **Excellent DX** (React hooks, beautiful pre-built UI)
✅ **Perfect for MVP** (10K MAUs covers initial coaches/athletes)
✅ **Backend SDK** (Python/FastAPI support for Cloud Run)

### Setup Complexity
⭐⭐⭐⭐⭐ (5/5) - Easiest

### Documentation
- [Vercel Integration](https://clerk.com/docs/integrations/vercel-marketplace)
- [FastAPI Backend](https://clerk.com/docs/backend-requests/handling/python)

---

## 2. Supabase (RECOMMENDED FOR SCALE)

### Free Tier (December 2025)
- **50,000 MAUs** per month
- 500 MB database storage
- 2 GB bandwidth
- Unlimited API requests
- Email + social auth included
- 2 projects per organization

### Paid Plans
- **Pro**: $25/month base
  - Includes 100,000 MAUs
  - Additional MAUs: $0.00325 per MAU

### Why Choose Supabase for Kinemotion
✅ **Most generous free tier** (50K MAUs)
✅ **Open source** (can self-host if needed)
✅ **Includes database** (Postgres - useful for user data)
✅ **Great for scale** (cheapest per-user cost)
✅ **Backend SDK** (Python client for Cloud Run)

### Setup Complexity
⭐⭐⭐⭐ (4/5) - Very good

### Documentation
- [Vercel Integration](https://supabase.com/docs/guides/getting-started/quickstarts/nextjs)
- [Python Client](https://supabase.com/docs/reference/python/introduction)

---

## 3. Auth0 (NOT RECOMMENDED - Expensive)

### Free Tier (December 2025)
- **25,000 MAUs** per month (expanded from 7,500)
- Basic authentication
- Social logins
- Community support

### Paid Plans
- **Essentials**: $35/month for 500 MAUs, then $0.07 per MAU
  - Example: 10,000 MAUs = $35 + (9,500 × $0.07) = $700/month 😱

### Why NOT Recommended
❌ **Expensive after free tier** ($700/month for 10K users)
❌ **Growth penalty** (costs scale poorly)
❌ **Complex pricing** (add-ons cost $100-200/month)

### When to Use Auth0
- Enterprise customers requiring SAML/OIDC
- Need advanced compliance features
- Already using Okta ecosystem

---

## 4. Firebase Auth

### Free Tier (December 2025)
- **50,000 MAUs** per month (email/password/social only)
- SAML/OIDC: 50 MAUs free
- Phone auth: NOT FREE (costs $0.06 per verification)

### Paid Plans
- Pay-as-you-go (no base fee)
- Phone auth: $0.06 per SMS verification
- Above 50K MAUs: Contact sales

### Why Choose Firebase
✅ **Very generous free tier** (50K MAUs)
✅ **Google infrastructure** (reliable)
✅ **Good Vercel integration**
✅ **Backend SDK** (Python Admin SDK)

### Why NOT Choose Firebase
❌ **Google ecosystem lock-in**
❌ **Phone auth costs extra** (could add up)
❌ **Less modern DX than Clerk**

---

## Decision Matrix for Kinemotion

### Current MVP Requirements
- 100 videos/day estimate
- ~500-1,000 MAUs initially (coaches + athletes)
- Vercel frontend + Cloud Run backend
- Need user ID logging (just implemented!)

### Recommendation by Stage

#### **Phase 1: MVP Launch (0-10K users)**
👉 **Use Clerk**
- Fastest setup (native Vercel integration)
- Beautiful pre-built UI
- Free for first 10K MAUs
- Perfect for MVP validation

**Cost: $0/month**

#### **Phase 2: Growth (10K-50K users)**
👉 **Stay with Clerk** OR **Switch to Supabase**

**Clerk pricing:**
- 20K MAUs = $25 + (10K × $0.02) = $225/month

**Supabase pricing:**
- 20K MAUs = $25/month (includes 100K MAUs!)

**Decision point:** If you hit 15K+ MAUs, Supabase becomes cheaper.

#### **Phase 3: Scale (50K+ users)**
👉 **Supabase** (open-source, better economics)

---

## Implementation Comparison

### Clerk Setup (Fastest)
```bash
# 1. Install from Vercel Marketplace (1-click)
# 2. Install frontend SDK
npm install @clerk/nextjs

# 3. Add backend validation (Cloud Run)
pip install clerk-backend-api
```

**Time to production: ~10 minutes**

### Supabase Setup (Very Fast)
```bash
# 1. Create Supabase project
# 2. Install frontend SDK
npm install @supabase/supabase-js

# 3. Add backend validation (Cloud Run)
pip install supabase
```

**Time to production: ~20 minutes**

---

## Final Recommendation for Kinemotion

### 🏆 **Start with Clerk**

**Why:**
1. Native Vercel integration (fastest path to production)
2. Beautiful pre-built UI (saves development time)
3. Free for first 10K MAUs (covers MVP validation)
4. Excellent documentation and support
5. Easy migration to Supabase later if needed

**Cost projection:**
- Month 1-6 (MVP): $0
- Month 7-12 (growth to 5K users): $0
- Month 13+ (10K-15K users): $25-125/month

### 🥈 **Alternative: Supabase**

**Choose if:**
- Want most generous free tier (50K MAUs)
- Plan to use Postgres database anyway
- Prefer open-source solutions
- Want cheapest long-term costs

---

## Next Steps

Once you choose, I can implement:
1. Frontend authentication (React hooks)
2. Backend token validation (FastAPI middleware)
3. User ID logging (already set up with structlog!)
4. Protected routes and API endpoints

**Which would you like to use: Clerk or Supabase?**
