SvelteKit error tracking installation

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  1. Install PostHog

    Required
    Your goal in this step: Install the PostHog JavaScript web and Node SDKs.

    Install posthog-js using your package manager:

    npm install --save posthog-js

    Then, if you haven't created a root layout already, create a new file called +layout.js in your src/routes folder In this file, check the environment is the browser, and initialize PostHog if so. You can get both your API key and instance address in your project settings.

    routes/+layout.js
    import posthog from 'posthog-js'
    import { browser } from '$app/environment';
    

    export const load = async () => {
      if (browser) {
        posthog.init('<ph_project_api_key>', {
          api_host: 'https://us.i.posthog.com',
          defaults: '2025-05-24',
        })
      }
    

      return
    };

    Install posthog-node using your package manager:

    npm install posthog-node --save

    Then, initialize the PostHog Node client where you'd like to use it on the server side. For example, in a load function:

    routes/+page.server.js
    import { PostHog } from 'posthog-node';
    

    export async function load() {
      const posthog = new PostHog('<ph_project_api_key>', { host: 'https://us.i.posthog.com' });
    

      posthog.capture({
        distinctId: 'distinct_id_of_the_user',
        event: 'event_name',
      })
    

      await posthog.shutdown()
    }

    Note: Make sure to always call posthog.shutdown() after capturing events from the server-side. PostHog queues events into larger batches, and this call forces all batched events to be flushed immediately.

  2. Set up client-side exception capture

    Required

    SvelteKit Hooks can be used to capture exceptions in the client and server-side.

    Capture exceptions in the handleError callback in your client-side hooks file:

    src/hooks.client.js
    import posthog from 'posthog-js';
    import type { HandleClientError } from '@sveltejs/kit';
    

    export const handleError = ({ error, status }: HandleClientError) => {
      // SvelteKit 2.0 offers a reliable way to check for a 404 error:
      if (status !== 404) {
          posthog.captureException(error);
      }
    };

  3. Set up server-side exception capture

    Required

    To capture exceptions on the server-side, you will also need to implement the handleError callback:

    src/hooks.server.ts
    import type { HandleServerError } from '@sveltejs/kit';
    import { PostHog } from 'posthog-node';
    

    const client = new PostHog(
      '<ph_project_api_key>',
      { host: 'https://us.i.posthog.com' }
    )
    

    export const handleError = async ({ error, status }: HandleServerError) => {
      if (status !== 404) {
          client.captureException(error);
          await client.shutdown();
      }
    };

  4. Verify error tracking

    Checkpoint
    Confirm events are being sent to PostHog

    Before proceeding, let's make sure exception events are being captured and sent to PostHog. You should see events appear in the activity feed.


    Activity feed with events
    Check for exceptions in PostHog

  5. Upload source maps

    Required

    Great, you're capturing exceptions! If you serve minified bundles, the next step is to upload source maps to generate accurate stack traces.

    Let's continue to the next section.

    Upload source maps

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Hono error tracking installation

Error tracking enables you to track, investigate, and resolve exceptions your customers face. Start by installing the posthog-node package using your package manager: Hono uses app.onError to handle uncaught exceptions. You can take advantage of this for error tracking. Remember to export your project API key as an environment variable.

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