SvelteKit error tracking installation

Install the package

Required

Install the PostHog JavaScript library using your package manager:

npm install posthog-js
yarn add posthog-js
pnpm add posthog-js

Initialize PostHog

Required

If you haven't created a root layout already, create a new file called +layout.js in your src/routes folder. Check the environment is the browser, and initialize PostHog if so:

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

export const load = async () => {
  if (browser) {
    posthog.init(
      '<ph_project_api_key>',
      {
        api_host: 'https://us.i.posthog.com',
        defaults: '2026-01-30'
      }
    )
  }

  return
};

SvelteKit layout

Learn more about SvelteKit layouts in the official documentation.

Server-side setup

Optional

Install posthog-node using your package manager:

npm install posthog-node --save
yarn add posthog-node
pnpm add posthog-node
bun add posthog-node

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.

Send events

Click around and view a couple pages to generate some events. PostHog automatically captures pageviews, clicks, and other interactions for you.

If you'd like, you can also manually capture custom events:

JavaScript
posthog.capture('my_custom_event', { property: 'value' })

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);
  }
};

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();
  }
};

Verify error tracking
Recommended
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.
Check for exceptions in PostHog
7
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

SvelteKit error tracking installation

Install the package

Initialize PostHog

Server-side setup

Send events

Set up client-side exception capture

Set up server-side exception capture

Verify error tracking

Upload source maps

Community questions

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