> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ledgersyncappv2.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Authentication

> Bearer keys, sandbox vs live, and how to keep them safe.

Every request carries your secret key as a Bearer token:

```bash theme={null}
curl https://api-sandbox.ledgersyncappv2.com/v3/clients \
  -H "Authorization: Bearer sk_test_..."
```

## Two environments, two key prefixes

<CardGroup cols={2}>
  <Card title="Sandbox" icon="flask">
    Keys start with **`sk_test_`**. Free, safe to experiment, routes to
    aggregator test banks. Base URL `https://api-sandbox.ledgersyncappv2.com/v3`.
  </Card>

  <Card title="Live" icon="rocket">
    Keys start with **`sk_live_`**. Real banks, real data. Base URL
    `https://api.ledgersyncappv2.com/v3`.
  </Card>
</CardGroup>

<Warning>
  Treat secret keys like passwords. Never embed them in mobile apps, browsers,
  or anything client-side, they belong on your server only. If a key leaks,
  roll it in the developer portal.
</Warning>

## End-user tokens

A few flows act on behalf of one specific end-user (for example, submitting an
MFA answer mid-connection). Those use a separate, short-lived token you mint
with your API key and hand to client-side code, never your `sk_` key itself.

## Getting a trace id

Every response includes an `X-LS-Trace-Id` header. Paste it into any support
request and we can jump straight to your exact call.