API Documentation: Domain Availability Checker

# Domain availability API

This API allows you to check the availability of a domain name. The API supports both **GET** and **POST** requests.

> **Note:** The API key shown in this documentation is for testing purposes only. Replace it with the API key found in your profile.

## Base URLs

### GET endpoint

```text
https://v2-api.domainduck.io/api/get/
```

### POST endpoint

```text
https://v2-api.domainduck.io/api/post/
```

---

# Examples

## Check domain availability

Request:

```text
https://v2-api.domainduck.io/api/get/?domain=example.com&apikey=VH2PS6QZ5FYD&use_cache=1
```

## Get WHOIS data as JSON

Request:

```text
https://v2-api.domainduck.io/api/get/?domain=example.com&apikey=VH2PS6QZ5FYD&whois=1
```

## Get raw WHOIS data

Request:

```text
https://v2-api.domainduck.io/api/get/?domain=example.com&apikey=VH2PS6QZ5FYD&whois=1&raw=1
```

---

# Response values

The API returns JSON responses describing domain availability.

## Availability status responses

| Status    | Description                                                                                 |
| --------- | ------------------------------------------------------------------------------------------- |
| `true`    | The domain is available for registration.                                                   |
| `false`   | The domain is already registered and unavailable.                                           |
| `premium` | The domain is available but offered as a premium domain by a registry or marketplace.       |
| `blocked` | The domain has been reserved or blocked by the registry and is not available to the public. |

### Examples

#### Available domain

```json
{
  "domain": "available-domain-123.com",
  "availability": "true"
}
```

#### Registered domain

```json
{
  "domain": "google.com",
  "availability": "false"
}
```

#### Premium domain

```json
{
  "domain": "flights.site",
  "availability": "premium",
  "price": 1625,
  "url": "namecheap.com/domains/registration/results/?domain=flights.site",
  "type": "buy now"
}
```

#### Blocked domain

```json
{
  "domain": "nic.kr",
  "availability": "blocked"
}
```

---

# Error responses

The API may return one of the following errors:

# Errors

| Error | Description | HTTP code |
|---|---|---|
| `rate limit exceeded` | The number of allowed API requests has been exceeded. | 429 |
| `bad tld` | The TLD is invalid or not supported. | 400 |
| `key invalid` | The API key is invalid. | 400 |
| `no permissions` | You are trying to access some functionality that your current plan does not support. | 400 |
| `out of credits` | You've used up all your available API requests. | 400 |
| `unknown error` | Unknown error. | 400 |
| `warning, estimated answer` | We got no answer from the registry or WHOIS server, so you got an estimated answer based on DNS and premium data. | 200 |

**Error example response:**

```json 
{"error":"key invalid"}
```

Http code = 400
---

# Parameters

| Parameter   | Type   | Required | Description                                                                         |
| ----------- | ------ | -------- | ----------------------------------------------------------------------------------- |
| `domain`    | string | Yes      | The domain name to check (e.g. `example.com`).                                      |
| `apikey`    | string | Yes      | Your unique API key.                                                                |
| `whois`     | bool   | No       | Return WHOIS information instead of availability data.                              |
| `raw`       | bool   | No       | Return only raw WHOIS/RDAP data.                                                    |
| `rdap`      | bool   | No       | Return RDAP information.                                                            |
| `use_cache` | bool   | No       | Enable cache mode. Cached requests are faster and cheaper but may be less accurate. |

---

# Usage

## PHP example (GET)

```php
 $domain,
    'apikey' => $apikey,
    'rand' => rand(1000000000, 9999999999),
];

// Init curl
$ch = curl_init();

// Set curl options
curl_setopt_array($ch, [
    CURLOPT_URL => $url,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => http_build_query($data),
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Content-Type: application/x-www-form-urlencoded',
    ],
]);

// Execute and fetch response
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    die('Curl error: ' . curl_error($ch));
}

curl_close($ch);

echo "API Response: " . $response;
```

---

# Notes

* Ensure your API key (`apikey`) is valid and active.
* Random values such as `rand` in the POST example are optional, but can help prevent caching issues.
* If you encounter `rate limit exceeded`, consider reducing your request frequency.
* For further assistance, contact support at `[email protected]`.

---

# Cache mode

Enable cache mode by adding the `use_cache` parameter.

## Benefits

* Faster response times
* Lower API costs
* Ideal for bulk domain availability checks

## Pricing

Cached requests are 10x cheaper than normal requests and consume only 0.1 API requests per lookup.

## Limitations

* Cached results may be up to 3 days old
* Results can occasionally be estimated or outdated
* Cache mode only works for availability checks
* Cache mode does not work with WHOIS lookups

---

# WHOIS data

Add the `whois` parameter to retrieve WHOIS information instead of availability data.

Example:

```php
$url = "https://v2-api.domainduck.io/api/get/?domain=$domain&apikey=$apikey&whois=1";
```

## Example response

```json
{
  "DomainName": "DN.COM",
  "UpdatedDate": "2026-05-06T03:59:50+00:00",
  "CreationDate": "1997-05-30T04:00:00+00:00",
  "ExpiryDate": "2034-05-29T04:00:00+00:00",
  "Registrar": "Alibaba Cloud Computing Ltd. d/b/a HiChina (www.net.cn)",
  "RegistrarAbuseEmail": "[email protected]",
  "RegistrarAbusePhone": "+86.95187",
  "NameServer": [
    "BED.DNSPOD.NET",
    "HAMILTION.DNSPOD.NET"
  ],
  "Contacts": [],
  "RawWhois": "[base64 encoded WHOIS data]",
  "QueryResult": "Record found"
}
```

## QueryResult

The `QueryResult` field indicates whether a WHOIS record was found.

| Value                 | Meaning                                       |
| --------------------- | --------------------------------------------- |
| `Record found`        | A WHOIS record exists for the domain.         |
| `No record (-)`       | No WHOIS record could be found.               |
| `No record (blocked)` | The domain is blocked by the registry.        |
| `No record (premium)` | The domain is classified as a premium domain. |

### RawWhois

The `RawWhois` field contains the original WHOIS response encoded as Base64.

To retrieve the raw WHOIS data without Base64 encoding, add the `raw=1` parameter:

```text
https://v2-api.domainduck.io/api/get/?domain=example.com&apikey=YOUR_API_KEY&whois=1&raw=1
```

---

# RDAP data

Some registries have discontinued WHOIS and migrated to RDAP.

For these TLDs:

* The API automatically returns RDAP data.
* The `RawWhois` key is replaced by `RawRdap`.
* The returned JSON follows the standard RDAP format.

If you always want RDAP data when available, use the `rdap` parameter instead of `whois`.

Example:

```text
https://v2-api.domainduck.io/api/get/?domain=example.com&apikey=YOUR_API_KEY&rdap=1
```

---

# Domain valuation / appraisals (Beta)

The API also supports approximate domain valuations in USD.

## Endpoints

### POST

```text
https://v2-api.domainduck.io/api/appraisal/post/
```

### GET

```text
https://v2-api.domainduck.io/api/appraisal/get/
```

> Returns an estimated market value for a domain name in USD.