PostHog Proxy

A lightweight reverse proxy for routing PostHog analytics through your own domain. This helps bypass ad blockers and increases event capture rates.

Why Use a Proxy?

Ad blockers often block requests to posthog.com. By proxying through your own domain, analytics requests appear as first-party traffic and are less likely to be blocked.

How It Works

The proxy routes requests to PostHog's infrastructure:

• /static/* → {region}-assets.i.posthog.com (JS SDK files)
• /* → {region}.i.posthog.com (events, feature flags, etc.)

Deployment

This is configured for Fly.io:

fly launch --no-deploy
fly deploy

The app will auto-stop when idle and auto-start on incoming requests to minimize costs.

CI/CD

Pushes to main automatically run tests and deploy to Fly.io via GitHub Actions.

To enable automatic deploys, add FLY_API_TOKEN to your repository secrets:

1. Generate a token: fly tokens create deploy -x 999999h
2. Add it to GitHub: Settings → Secrets and variables → Actions → New repository secret

Configuration

Environment Variables

Variable	Default	Description
POSTHOG_REGION	us	PostHog region: us or eu

Set the region in fly.toml or via fly secrets set POSTHOG_REGION=eu.

Client Setup

Configure the PostHog SDK to use your proxy:

posthog.init("YOUR_PROJECT_KEY", {
  api_host: "https://your-app-name.fly.dev",
  ui_host: "https://us.posthog.com", // or eu.posthog.com
});

Local Development

Requires Go 1.22. Use mise to install:

mise install

Make Targets

Command	Description
make build	Compile the binary
make test	Run tests
make run	Run the proxy locally
make clean	Remove the built binary

Verification

1. Check the health endpoint: curl https://your-app-name.fly.dev/health
2. Configure your app's PostHog SDK with the proxy URL
3. Verify events appear in your PostHog dashboard