diff --git a/README.md b/README.md
index 6db8b92..70345d2 100644
--- a/README.md
+++ b/README.md
@@ -92,6 +92,7 @@ Same for IPv6 prefixes like _2001:db8:a0b:12f0::/64_.
 
 ### 1.6.0 / unreleased ###
 * Minor accessibility fixes on settings page
+* Introduced new user agent filter (#20)
 
 ### 1.5.2 / 03.09.2020 ###
 * Minor translation updates
diff --git a/inc/class-statifyblacklist.php b/inc/class-statifyblacklist.php
index 97b9c89..9b01bb7 100644
--- a/inc/class-statifyblacklist.php
+++ b/inc/class-statifyblacklist.php
@@ -91,7 +91,10 @@ class StatifyBlacklist {
 		self::update_options();
 
 		// Add Filter to statify hook if enabled.
-		if ( 0 !== self::$options['referer']['active'] || 0 !== self::$options['target']['active'] || 0 !== self::$options['ip']['active'] ) {
+		if ( 0 !== self::$options['referer']['active'] ||
+			0 !== self::$options['target']['active'] ||
+			0 !== self::$options['ip']['active'] ||
+			0 !== self::$options['ua']['active'] ) {
 			add_filter( 'statify__skip_tracking', array( 'StatifyBlacklist', 'apply_blacklist_filter' ) );
 		}
 
@@ -156,6 +159,11 @@ class StatifyBlacklist {
 				'active'    => 0,
 				'blacklist' => array(),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => 0,
+				'blacklist' => array(),
+			),
 			'version' => self::VERSION_MAIN,
 		);
 	}
@@ -264,6 +272,59 @@ class StatifyBlacklist {
 			}
 		}
 
+		// User agent filter (since 1.6).
+		if ( isset( self::$options['ua']['active'] ) && 0 !== self::$options['ua']['active'] ) {
+			// Determine filter mode.
+			$mode = isset( self::$options['ua']['regexp'] ) ? intval( self::$options['ua']['regexp'] ) : 0;
+
+			// Get full user agent string.
+			if ( ! empty( $_SERVER['HTTP_USER_AGENT'] ) ) {
+				$user_agent = filter_var( wp_unslash( $_SERVER['HTTP_USER_AGENT'] ), FILTER_SANITIZE_STRING );
+
+				if ( $user_agent ) {
+					switch ( $mode ) {
+
+						// Regular Expression filtering since 1.3.0.
+						case self::MODE_REGEX:
+						case self::MODE_REGEX_CI:
+							// Merge given regular expressions into one.
+							$regexp = self::regex(
+								array_keys( self::$options['ua']['blacklist'] ),
+								self::MODE_REGEX_CI === self::$options['ua']['regexp']
+							);
+
+							// Check filter (no return to continue filtering #12).
+							if ( 1 === preg_match( $regexp, $user_agent ) ) {
+								return true;
+							}
+							break;
+
+						// Keyword filter since 1.5.0 (#15).
+						case self::MODE_KEYWORD:
+							// Get filter.
+							$blacklist = self::$options['ua']['blacklist'];
+
+							foreach ( array_keys( $blacklist ) as $keyword ) {
+								if ( false !== strpos( strtolower( $user_agent ), strtolower( $keyword ) ) ) {
+									return true;
+								}
+							}
+							break;
+
+						// Standard exact filter.
+						default:
+							// Get filter.
+							$blacklist = self::$options['ua']['blacklist'];
+
+							// Check filter.
+							if ( isset( $blacklist[ $user_agent ] ) ) {
+								return true;
+							}
+					}
+				}
+			}
+		}
+
 		// Skip and continue (return NULL), if all filters are inactive.
 		return null;
 	}
diff --git a/test/StatifyBlacklist_Test.php b/test/StatifyBlacklist_Test.php
index e896199..2742c4e 100644
--- a/test/StatifyBlacklist_Test.php
+++ b/test/StatifyBlacklist_Test.php
@@ -68,6 +68,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 				'active'    => 0,
 				'blacklist' => array(),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
@@ -130,6 +135,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 				'active'    => 0,
 				'blacklist' => array(),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
@@ -187,6 +197,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 				'active'    => 0,
 				'blacklist' => array(),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
@@ -426,6 +441,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 					'2001:db8:a0b:12f0::1',
 				),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
@@ -498,6 +518,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 				'active'    => 0,
 				'blacklist' => array(),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
@@ -544,6 +569,69 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 	// TODO: Test target regex filter.
 
 
+	/**
+	 * Test user agent filter (#20).
+	 *
+	 * @return void
+	 */
+	public function test_ua_filter() {
+		// Prepare Options: 2 filtered IPs, disabled.
+		StatifyBlacklist::$options = array(
+			'referer' => array(
+				'active'    => 0,
+				'cron'      => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
+			'target'  => array(
+				'active'    => 0,
+				'cron'      => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
+			'ip'      => array(
+				'active'    => 0,
+				'blacklist' => array(),
+			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(
+					'TestBot/1.23' => 0,
+				),
+			),
+			'version' => StatifyBlacklist::VERSION_MAIN,
+		);
+
+		// No multisite.
+		StatifyBlacklist::$multisite = false;
+
+		// Set matching user agent.
+		$_SERVER['HTTP_USER_AGENT'] = 'TestBot/1.23';
+		$this->assertNull( StatifyBlacklist::apply_blacklist_filter() );
+		// Activate filter.
+		StatifyBlacklist::$options['ua']['active'] = 1;
+		$this->assertTrue( StatifyBlacklist::apply_blacklist_filter() );
+		// Non-matching addresses.
+		$_SERVER['HTTP_USER_AGENT'] = 'Another Browser 4.5.6 (Linux)';
+		$this->assertNull( StatifyBlacklist::apply_blacklist_filter() );
+		$_SERVER['HTTP_USER_AGENT'] = 'TestBot/2.34';
+		$this->assertNull( StatifyBlacklist::apply_blacklist_filter() );
+		// Keyword matching.
+		StatifyBlacklist::$options['ua']['blacklist'] = array( 'TestBot' => 0 );
+		StatifyBlacklist::$options['ua']['regexp'] = StatifyBlacklist::MODE_KEYWORD;
+		$this->assertTrue( StatifyBlacklist::apply_blacklist_filter() );
+		// RegEx.
+		StatifyBlacklist::$options['ua']['blacklist'] = array( 'T[a-z]+B[a-z]+' => 0 );
+		StatifyBlacklist::$options['ua']['regexp'] = StatifyBlacklist::MODE_REGEX;
+		$this->assertTrue( StatifyBlacklist::apply_blacklist_filter() );
+		StatifyBlacklist::$options['ua']['blacklist'] = array( 't[a-z]+' => 0 );
+		$this->assertNull( StatifyBlacklist::apply_blacklist_filter() );
+		StatifyBlacklist::$options['ua']['regexp'] = StatifyBlacklist::MODE_REGEX_CI;
+		$this->assertTrue( StatifyBlacklist::apply_blacklist_filter() );
+	}
+
+
 	/**
 	 * Test combined filters.
 	 *
@@ -576,6 +664,11 @@ class StatifyBlacklist_Test extends PHPUnit\Framework\TestCase {
 					'192.0.2.123',
 				),
 			),
+			'ua'      => array(
+				'active'    => 0,
+				'regexp'    => StatifyBlacklist::MODE_NORMAL,
+				'blacklist' => array(),
+			),
 			'version' => StatifyBlacklist::VERSION_MAIN,
 		);
 
diff --git a/views/settings-page.php b/views/settings-page.php
index 5a61c82..b7debe2 100755
--- a/views/settings-page.php
+++ b/views/settings-page.php
@@ -88,6 +88,26 @@ if ( ! empty( $_POST['statifyblacklist'] ) ) {
 			);
 		}
 
+		// TODO: Extract user agent array.
+		if ( isset( $_POST['statifyblacklist']['ua']['blacklist'] ) ) {
+			$ua_string = sanitize_textarea_field( wp_unslash( $_POST['statifyblacklist']['ua']['blacklist'] ) );
+		}
+		if ( empty( trim( $ua_string ) ) ) {
+			$ua = array();
+		} else {
+			$ua = array_filter(
+				array_map(
+					function ( $a ) {
+						return trim( $a );
+					},
+					explode( "\r\n", str_replace( '\\\\', '\\', $ua_string ) )
+				),
+				function ( $a ) {
+					return ! empty( $a );
+				}
+			);
+		}
+
 		// Update options (data will be sanitized).
 		$statifyblacklist_update_result = StatifyBlacklist_Admin::update_options(
 			array(
@@ -114,6 +134,13 @@ if ( ! empty( $_POST['statifyblacklist'] ) ) {
 						? (int) $_POST['statifyblacklist']['ip']['active'] : 0,
 					'blacklist' => $ip,
 				),
+				'ua'      => array(
+					'active'    => isset( $_POST['statifyblacklist']['ua']['active'] )
+						? (int) $_POST['statifyblacklist']['ua']['active'] : 0,
+					'regexp'    => isset( $_POST['statifyblacklist']['ua']['regexp'] )
+						? (int) $_POST['statifyblacklist']['ua']['regexp'] : 0,
+					'blacklist' => $ua,
+				),
 				'version' => StatifyBlacklist::VERSION_MAIN,
 			)
 		);
@@ -374,6 +401,77 @@ if ( ! empty( $_POST['statifyblacklist'] ) ) {
 			</tbody>
 		</table>
 
+		<h2><?php esc_html_e( 'User agent filter', 'statify-blacklist' ); ?></h2>
+
+		<table class="form-table">
+			<tbody>
+			<tr>
+				<th scope="row">
+					<label for="statify-blacklist_active_ua">
+						<?php esc_html_e( 'Activate live filter', 'statify-blacklist' ); ?>
+					</label>
+				</th>
+				<td>
+					<input type="checkbox" name="statifyblacklist[ua][active]" id="statify-blacklist_active_ua"
+						   value="1" <?php checked( StatifyBlacklist::$options['ua']['active'], 1 ); ?>>
+					<p class="description">
+						<?php esc_html_e( 'Filter at time of tracking, before anything is stored', 'statify-blacklist' ); ?>
+						<br>
+						<?php esc_html_e( 'Cron execution is not possible for user agent filter, because the user agent is stored.', 'statify-blacklist' ); ?>
+					</p>
+				</td>
+			</tr>
+			<tr>
+				<th scope="row">
+					<label for="statify-blacklist_ua_regexp"><?php esc_html_e( 'Matching method', 'statify-blacklist' ); ?></label>
+				</th>
+				<td>
+					<select name="statifyblacklist[ua][regexp]" id="statify-blacklist_ua_regexp">
+						<option value="<?php print esc_attr( StatifyBlacklist::MODE_NORMAL ); ?>" <?php selected( StatifyBlacklist::$options['ua']['regexp'], StatifyBlacklist::MODE_NORMAL ); ?>>
+							<?php esc_html_e( 'Exact', 'statify-blacklist' ); ?>
+						</option>
+						<option value="<?php print esc_attr( StatifyBlacklist::MODE_KEYWORD ); ?>" <?php selected( StatifyBlacklist::$options['ua']['regexp'], StatifyBlacklist::MODE_KEYWORD ); ?>>
+							<?php esc_html_e( 'Keyword', 'statify-blacklist' ); ?>
+						</option>
+						<option value="<?php print esc_attr( StatifyBlacklist::MODE_REGEX ); ?>" <?php selected( StatifyBlacklist::$options['ua']['regexp'], StatifyBlacklist::MODE_REGEX ); ?>>
+							<?php esc_html_e( 'RegEx case-sensitive', 'statify-blacklist' ); ?>
+						</option>
+						<option value="<?php print esc_attr( StatifyBlacklist::MODE_REGEX_CI ); ?>" <?php selected( StatifyBlacklist::$options['ua']['regexp'], StatifyBlacklist::MODE_REGEX_CI ); ?>>
+							<?php esc_html_e( 'RegEx case-insensitive', 'statify-blacklist' ); ?>
+						</option>
+					</select>
+
+					<p class="description">
+						<?php esc_html_e( 'Exact', 'statify-blacklist' ); ?> - <?php esc_html_e( 'Match only given user agents', 'statify-blacklist' ); ?>
+						<br>
+						<?php esc_html_e( 'Keyword', 'statify-blacklist' ); ?> - <?php esc_html_e( 'Match every referer that contains one of the keywords', 'statify-blacklist' ); ?>
+						<br>
+						<?php esc_html_e( 'RegEx', 'statify-blacklist' ); ?> - <?php esc_html_e( 'Match user agent by regular expression', 'statify-blacklist' ); ?>
+					</p>
+				</td>
+			</tr>
+			<tr>
+				<th scope="row">
+					<label for="statify-blacklist_ua"><?php esc_html_e( 'User agent filter', 'statify-blacklist' ); ?></label>:
+				</th>
+				<td>
+					<textarea cols="40" rows="5" name="statifyblacklist[ua][blacklist]" id="statify-blacklist_ua"><?php
+					if ( empty( $statifyblacklist_update_result['ua'] ) ) {
+						print esc_html( implode( "\r\n", StatifyBlacklist::$options['ua']['blacklist'] ) );
+					} else {
+						print esc_html( implode( "\r\n", $statifyblacklist_update_result['ua']['sanitized'] ) );
+					}
+					?></textarea>
+
+					<p class="description">
+						<?php esc_html_e( 'Add one user agent string per line, e.g.', 'statify-blacklist' ); ?>
+						MyBot/1.23
+					</p>
+				</td>
+			</tr>
+			</tbody>
+		</table>
+
 		<p class="submit">
 			<input class="button-primary" type="submit" name="submit" value="<?php esc_html_e( 'Save Changes', 'statify-blacklist' ); ?>">
 			<hr>