Railway reverse proxy

Before you start
  • If you use a self-hosted proxy, PostHog can't help troubleshoot. Use our managed reverse proxy if you want support.
  • Use domains matching your PostHog region: us.i.posthog.com for US, eu.i.posthog.com for EU.
  • Don't use obvious path names like /analytics, /tracking, /telemetry, or /posthog. Blockers will catch them. Use something unique to your app instead.

This guide shows you how to deploy a PostHog reverse proxy on Railway.

How it works

Railway provides a one-click deployment template that runs an nginx-based reverse proxy. When deployed, Railway gives you a domain that routes all requests to PostHog's servers.

Here's the request flow:

  1. User triggers an event in your app
  2. Request goes to your Railway domain (e.g., your-project.up.railway.app)
  3. The nginx proxy running on Railway forwards the request to PostHog
  4. PostHog processes the request and returns a response
  5. The proxy returns PostHog's response to the user

This works because ad blockers see requests going to Railway's domain (or your custom domain), not PostHog's.

Prerequisites

This guide requires a Railway account (free tier works).

Setup

  1. Deploy the template

    Click the button below to deploy a pre-configured PostHog reverse proxy on Railway:

    Deploy on Railway

    This template deploys an nginx container configured to proxy requests to PostHog.

  2. Configure your region

    During deployment, Railway prompts you to set the POSTHOG_CLOUD_REGION environment variable:

    • Set to us for US region
    • Set to eu for EU region

    This tells the proxy which PostHog servers to forward requests to. Make sure this matches your PostHog project's region.

  3. Wait for deployment

    Railway automatically builds and deploys your proxy. This usually takes 1-2 minutes.

    Once deployed, Railway provides you with a domain like your-project-name.up.railway.app. You can find this in your project's Settings → Networking section.

  4. Update your PostHog SDK

    In your application code, update your PostHog initialization to use your Railway domain:

    posthog.init('<ph_project_api_key>', {
      api_host: 'https://your-project-name.up.railway.app',
      ui_host: 'https://us.posthog.com'
    })

    Replace your-project-name.up.railway.app with your actual Railway domain.

  5. Add a custom domain

    Optional

    For better blocking resistance, use your own domain instead of Railway's default:

    1. Go to your Railway project's Settings → Networking
    2. Click Add Domain
    3. Follow Railway's custom domains guide to configure DNS

    Then update your SDK to use your custom domain:

    posthog.init('<ph_project_api_key>', {
      api_host: 'https://e.yourdomain.com',
      ui_host: 'https://us.posthog.com'
    })

  6. Verify your setup

    Checkpoint

    Confirm events are flowing through your proxy:

    1. Test the proxy directly:

      Terminal
      curl -I https://your-project-name.up.railway.app/decide?v=3

      You should see a 200 OK response.

    2. Open your browser's developer tools and go to the Network tab

    3. Trigger an event in your app

    4. Look for requests to your Railway domain

    5. Verify the response status is 200 OK

    6. Check the PostHog app to confirm events appear

    If you see errors, check troubleshooting below.

Troubleshooting

Proxy stops working periodically

If your proxy stops responding intermittently:

  1. Check sleep settings: Free tier services may sleep after inactivity. Go to Settings → Service and check if sleep mode is enabled.
  2. Monitor resource usage: Check the Metrics tab for memory or CPU spikes that might cause restarts.
  3. View logs: Look for error messages in the Deployments tab.
  4. Consider upgrading: Paid plans include better uptime guarantees and disable sleep mode.

If issues persist, check Railway's status page.

Deployment failed

If the initial deployment fails:

  1. Check the build logs for error messages
  2. Verify you set the POSTHOG_CLOUD_REGION variable correctly (must be us or eu)
  3. Try redeploying from the Railway dashboard

502 Bad Gateway errors

If the proxy returns 502 errors:

  1. Verify the POSTHOG_CLOUD_REGION variable matches your PostHog project's region
  2. Check that the Railway service is running in the dashboard
  3. View the service logs for connection errors

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