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

# GET /api/aliases/check

> Checks whether a handle alias is available before claiming it during HyperAuth registration, returning availability and the canonical alias hash.

Checks whether a handle alias is available for registration. Queries the global `SESSION_DB` D1 database directly.

## Query parameters

| Parameter | Type     | Required | Description                                |
| --------- | -------- | -------- | ------------------------------------------ |
| `alias`   | `string` | Yes      | Handle to check (lowercased before lookup) |

## Response — available

```json theme={null}
{ "available": true }
```

## Response — taken

```json theme={null}
{ "available": false, "did": "did:new:0x..." }
```

## Errors

| Code  | `error`                            | Condition        |
| ----- | ---------------------------------- | ---------------- |
| `400` | `"Missing query parameter: alias"` | Parameter absent |