---
title: "Check a licence key"
description: "Before adding keys: which of these keys already exist under any of these tags. Answers {duplicates: [key, ...]}; nothing is written."
url: https://docs.filemonk.io/v2/api-reference/licences/check-a-licence-key/
api: "API v2 reference"
method: POST
path: "/licences/check"
---

# Check a licence key

`POST https://app.filemonk.io/api/v2/external/licences/check`

Before adding keys: which of these keys already exist under any of these tags. Answers {duplicates: [key, ...]}; nothing is written.

## Request body

- `keys` (array of strings, required)
- `tags` (array of strings, required)

## Returns

- `duplicates` (array of strings, required)

Rate limit: this call costs 2 points ([rate limits](https://docs.filemonk.io/v2/errors-and-rate-limits/)).

## Example request

```sh
curl -X POST "https://app.filemonk.io/api/v2/external/licences/check" \
  -H "X-Auth-Token: $FILEMONK_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "keys": [
      "ABCD-EFGH-IJKL-0001",
      "ABCD-EFGH-0005"
    ],
    "tags": [
      "ebook-2026"
    ]
  }'
```

## 200

Success: the write completed; the body is the updated resource.

```json
{
  "duplicates": [
    "ABCD-EFGH-0005"
  ]
}
```

## 401

Missing or invalid API key.

```json
{
  "errors": [
    "Invalid API key"
  ]
}
```

## 422

The request failed validation, or sent a key the action does not take (`code: "unknown_parameters"` with `unknown` and `accepted`). Nothing was saved.

```json
{
  "errors": [
    "access.download_limit_count must be an integer of at least 0"
  ],
  "field_errors": {
    "access.download_limit_count": [
      "must be an integer of at least 0"
    ]
  }
}
```

## 429

Rate limited. Cost-weighted per API key, shared with API v1: a read costs 1 point, a write 2, 40 points per fixed 60-second window. Every response carries `X-RateLimit-Limit`, `X-RateLimit-Remaining` and `X-RateLimit-Reset` (Unix time the window ends); a 429 adds `Retry-After` (seconds), `retry_after`, `retryable: true` and a `next_step` in the body. A 429 did nothing: wait `retry_after` seconds, then send the same request again. The budget is per key, so every tool or script using the key shares it; prefer one list call with `per_page` over many single reads.

```json
{
  "errors": [
    "You have exceeded the rate limit of 40 points per 60 seconds. Read requests cost 1 point(s) and write requests cost 2 point(s). Please retry after 12 second(s)."
  ],
  "code": "rate_limited",
  "retry_after": 12,
  "error": "Rate limit exceeded",
  "message": "You have exceeded the rate limit of 40 points per 60 seconds. Read requests cost 1 point(s) and write requests cost 2 point(s). Please retry after 12 second(s)."
}
```