On March 17th, 2017 the official documentation of the API has been removed. On May 20th the documentation has moved to http://site.nicovideo.jp/search-api-docs/search.html

On the 29th of May, the services game and license_search were added

On the 3rd of August, the service mylist_video was added and a description of jsonFilter was added

On the 4th of October, the service book was removed.

API Documentation

URL Parameter

The generic endpoint of the API is http://api.search.nicovideo.jp/api/v2/:service/contents/search. The API can be called to retrieve information from the following services:

Replace :service with the name of a service.

Query Arguments

The options of the search request are encoded using query arguments through the GET method.

Mandatory Arguments

• q : Search Keywords
• targets : Search Objects (Separated by a comma, one or many of the following: title, tags, description and tagsExact)
• fields : Content Fields of the hits returned (Separated by a comma, one or many of the following: contentId, title, description, tags, categoryTags, viewCounter, mylistCounter, commentCounter, startTime, communityIcon, liveStatus)
• _sort : Sort Method (' ' or '-' for the order, one of the following : viewCounter, mylistCounter, commentCounter, startTime, thumbnailUrl, scoreTimeshiftReserved)

Optionial Arguments

• filters : Search Filters (The following fields can be used to filter: contentId, tags, categoryTags, viewCounter, mylistCounter, commentCounter, startTime, liveStatus)
• _limit : Number of hits returned (10 by default, 100 maximum)
• _offset : Number of hits skipped (0 by default, 1600 maximum)
• _context : Service/Application Name (Maximum length of 40 characters)

Response

The API will return the following JSONs.

On success

On failure

Example Application

We are going to write a simple application to retrive the most recent pictures of Miku Hatsune and generate a small gallery.

First, we gather the url and the options.

$basic_url = "http://api.search.nicovideo.jp/api/v2/:service/contents/search";
$options = [
    "q" => "初音ミク",                  // Search Keyword
    "targets" => "title,tags",         // Search Object
    "fields" => "contentId,title,tags",// Fields of the hits returned
    "_sort" => "-startTime",           // Sort Method
    "_limit" => 12,                    // Number of hits returned
    "_offset" => 0,                    // Number of hits skipped
    "_context" => "apiguide"           // Service/Application Name
];

Then replace :service with the name of the desired service.

$url = str_replace(":service", "illust", "http://api.search.nicovideo.jp/api/v2/:service/contents/search");

Assemble the query parameters from the array and execute the query.

$parameters = "?";
$ctr = 1;
$length = count($options);
foreach ($options as $name => $value) {
    $parameters .= $name . "=" . urlencode($value);

    if ($ctr < $length) {
        $parameters .= &#39;&&#39;;
    }
    $ctr  ;
}

$request = $url . $parameters;
$response = file_get_contents($request);
$json_response = json_decode($response);

if (json_last_error() !== JSON_ERROR_NONE) {
    die(json_last_error_msg());
} else {
    if (isset($json_response->meta)) {
        if ($json_response->meta->status == 200) {
            // Success
        } else {
            // Failure
        }
    } else {
        // Failure
    }
}

The query string produced will be similar to this :

http://api.search.nicovideo.jp/api/v2/illust/contents/search?q=初音ミク&targets=title,tags&fields=contentId,title,tags&_sort=-startTime&_limit=12&_offset=0&_context=apiguide

The response must be a JSON object otherwise the query has failed. If the status is 200 the query is successful and therefore you can parse the results.

$data = array();

foreach ($json_response->data as $item) {
    $data[] = (object) (array) $item;
}

$total = $json_response->meta->totalCount;

Now you can invoke a view to display the results. Here's an example view for this example. It will print the thumbnail of the illustration with a link to visit the page on niconico Seiga.

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Nicovideo Contents Search API Example</title>
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet" />
</head>
<body>
<div class="container">
    <div class="row">
        <?php foreach ($data as $item) : ?>
            <div class="col-xs-6 col-sm-3 col-md-2">
                <a class="thumbnail" href="<?= "http://seiga.nicovideo.jp/image/source/" . preg_replace("/[^0-9]/", "", $item->contentId) ?>" target="_blank">
                    <img title="<?= $item->title ?>" src="<?= str_replace(":img_num_id", preg_replace("/[^0-9]/", "", $item->contentId), ""http://lohas.nicoseiga.jp/thumb/:img_num_idcz") ?>" style="width:100%">
                </a>
            </div>
        <?php endforeach; ?>
    </div>
</div>
<script src="https://code.jquery.com/jquery-1.12.2.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
</body>
</html>

See A More Complete Example

For more documentation on the API and more advanced features like filters, view the official documentation in Japanese of the API here : http://search.nicovideo.jp/docs/api/search.html