Using Vercel rewrites as a reverse proxy

Note: If you are using the EU cloud then use eu instead of us in all domains (e.g. us.i.posthog.com -> eu.i.posthog.com)

Vercel supports rewrites which we can use as a reverse proxy. Create a vercel.json file and add a rewrites object from the /ingest route.

{
  "rewrites": [
    {
      "source": "/ingest/static/:path*",
      "destination": "https://us-assets.i.posthog.com/static/:path*"
    },
    {
      "source": "/ingest/:path*",
      "destination": "https://us.i.posthog.com/:path*"
    }
  ]
}

Some frameworks, like SvelteKit and Astro, require a hungrier regex pattern like:

{
  "rewrites": [
    {
      "source": "/ingest/static/:path(.*)",
      "destination": "https://us-assets.i.posthog.com/static/:path*"
    },
    {
      "source": "/ingest/:path(.*)",
      "destination": "https://us.i.posthog.com/:path*"
    }
  ]
}

Note: Some frameworks, like T3 app, don't support Vercel rewrites well. If neither of these options work, we recommend trying another proxy method.

Once done, set the /ingest route of your domain as the API host in your PostHog initialization like this:

posthog.init('<ph_project_api_key>',
  {
    api_host: 'https://www.your-domain.com/ingest',
    ui_host: 'https://app.posthog.com' // or 'https://eu.posthog.com' if your PostHog is hosted in Europe
  }
)

Once updated, deploy your changes on Vercel and check that PostHog requests are going to https://www.your-domain.com/ingest by checking the network tab on your domain.

Setup video