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Export to PostHog

PostHog is a product analytics platform that helps you understand user behavior and debug issues. By exporting your Cloudflare Workers application telemetry to PostHog, you can:

• Correlate logs with user sessions, events, and error tracking data
• Query and filter logs by severity, attributes, and custom properties
• Connect application logs to session replays for full debugging context

This guide will walk you through configuring your Cloudflare Worker application to export OpenTelemetry-compliant logs to PostHog.

Before you begin, ensure you have:

• An active PostHog account ↗ (free tier available)
• A deployed Worker that you want to monitor
• Your PostHog project API key

1. Log in to your PostHog account ↗
2. Navigate to the Project settings ↗
3. Find your Project API key in the project details section
4. Copy the API key - this is the same key used for capturing events and exceptions

The API key should look something like: phc_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

PostHog has different endpoints depending on your data region:

You can find your region in your PostHog project settings or by checking the URL when logged into PostHog (either us.posthog.com or eu.posthog.com).

Now you'll create a destination in the Cloudflare dashboard that points to PostHog.

1. Navigate to your Cloudflare account's Workers Observability ↗ section
2. Click Add destination
3. Configure your logs destination:
   • Destination Name: posthog-logs (or any descriptive name)
   • Destination Type: Select Logs
   • OTLP Endpoint: Your PostHog logs endpoint (e.g., https://us.i.posthog.com/i/v1/logs or https://eu.i.posthog.com/i/v1/logs)
   • Custom Headers: Add the authentication header:
     • Header name: Authorization
     • Header value: Bearer <your-project-api-key> (e.g., Bearer phc_xxxxx...)
4. Click Save

With your destination created in the Cloudflare dashboard, update your Worker's configuration to enable logs export.

{
  "observability": {
    "logs": {
      "enabled": true,
      // Must match the destination name in the dashboard
      "destinations": ["posthog-logs"]
    }
  }
}

[observability.logs]
enabled = true
destinations = [ "posthog-logs" ]

After updating your configuration, deploy your Worker for the changes to take effect.

Once your Worker is deployed and receiving traffic:

1. Log in to your PostHog account ↗
2. Navigate to the Logs section in the left sidebar
3. Your Worker logs will appear with severity levels, timestamps, and attributes

You can filter logs by:

• Severity level (trace, debug, info, warn, error, fatal)
• Time range
• Custom attributes added to your log entries
• Keywords in log messages

You can add custom attributes to your logs using standard console methods with structured data:

export default {
  async fetch(request, env) {
    // Basic logging
    console.log("Processing request");

    // Logs with additional context
    console.info("User action", {
      userId: "user_123",
      action: "api_call",
      path: new URL(request.url).pathname
    });

    // Error logging with details
    console.error("Request failed", {
      error: "Connection timeout",
      retryCount: 3
    });

    return new Response("OK");
  }
};

These attributes will be searchable and filterable in the PostHog logs interface.

1. Verify your API key: Ensure you're using your project API key (starts with phc_), not a personal API key
2. Check the endpoint region: Confirm you're using the correct regional endpoint (US or EU) matching your PostHog instance
3. Confirm destination status: In the Cloudflare dashboard, verify your destination shows a recent successful delivery
4. Check sampling rate: If you've configured a sampling rate, not all logs may be sent

If you see authentication errors in your destination status:

• Ensure the Authorization header value includes Bearer prefix followed by your API key
• Verify the API key has not been revoked or regenerated in PostHog
• Alternatively, you can pass the token as a query parameter by using https://us.i.posthog.com/i/v1/logs?token=<your-project-api-key> as your endpoint

• PostHog Logs documentation ↗
• PostHog Getting Started with Logs ↗
• OpenTelemetry Logs specification ↗