diff --git a/autoload.php b/autoload.php
new file mode 100644
index 0000000..ecee5f0
--- /dev/null
+++ b/autoload.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Autoloader for WordPress.
+ */
+
+namespace StringLocator;
+
+use function spl_autoload_register;
+
+spl_autoload_register(
+	/**
+	 * Closure for the autoloader.
+	 *
+	 * @param class-string $class_name The fully-qualified class name.
+	 * @return void
+	 */
+	static function ( $class_name ) {
+		/**
+		 * __NAMESPACE__ could be an empty string.
+		 *
+		 * @phpstan-ignore-next-line
+		 */
+		$project_namespace = '' === __NAMESPACE__ ? '' : __NAMESPACE__ . '\\';
+		$length            = strlen( $project_namespace );
+
+		// Class is not in our namespace.
+		if ( 0 !== strncmp( $project_namespace, $class_name, $length ) ) {
+			return;
+		}
+
+		// E.g. Model\Item.
+		$relative_class_name = substr( $class_name, $length );
+		// Class file names should be based on the class name with "class-" prepended
+		// and the underscores in the class name replaced with hyphens.
+		// E.g. model/class-item.php.
+		$name_parts = explode( '\\', strtolower( str_replace( '_', '-', $relative_class_name ) ) );
+		$last_part  = array_pop( $name_parts );
+
+		$file = sprintf(
+			'%1$s/includes%2$s/class-%3$s.php',
+			__DIR__,
+			array() === $name_parts ? '' : '/' . implode( '/', $name_parts ),
+			$last_part
+		);
+
+		if ( ! is_file( $file ) ) {
+			return;
+		}
+
+		require $file;
+	}
+);
diff --git a/includes/Extension/SQL/sql.php b/includes/Extension/SQL/sql.php
deleted file mode 100644
index 40939ce..0000000
--- a/includes/Extension/SQL/sql.php
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-/**
- * Plugin Name: String Locator: SQL search module
- */
-
-namespace StringLocator\Extension\SQL;
-
-function validate_sql_fields( $field ) {
-	return preg_match( '/^[0-9a-zA-Z_]+$/s', $field );
-}
-
-require_once __DIR__ . '/class-search.php';
-require_once __DIR__ . '/class-edit.php';
-require_once __DIR__ . '/class-save.php';
-
-require_once __DIR__ . '/Tests/class-serialized-data.php';
diff --git a/includes/Extension/SearchReplace/search-replace.php b/includes/Extension/SearchReplace/search-replace.php
deleted file mode 100644
index 3835fa3..0000000
--- a/includes/Extension/SearchReplace/search-replace.php
+++ /dev/null
@@ -1,16 +0,0 @@
-<?php
-/**
- * Plugin Name: String Locator: Replacement module
- */
-
-namespace StringLocator\Extension\SearchReplace;
-
-// Primary extension class.
-require_once __DIR__ . '/class-replace.php';
-
-// Replacement handlers.
-require_once __DIR__ . '/Replace/class-file.php';
-require_once __DIR__ . '/Replace/class-sql.php';
-
-// REST Endpoints.
-require_once __DIR__ . '/REST/class-replace.php';
diff --git a/includes/Base/class-rest.php b/includes/base/class-rest.php
similarity index 100%
rename from includes/Base/class-rest.php
rename to includes/base/class-rest.php
diff --git a/includes/Base/class-search.php b/includes/base/class-search.php
similarity index 100%
rename from includes/Base/class-search.php
rename to includes/base/class-search.php
diff --git a/includes/Extension/SearchReplace/class-replace.php b/includes/extension/searchreplace/class-replace.php
similarity index 100%
rename from includes/Extension/SearchReplace/class-replace.php
rename to includes/extension/searchreplace/class-replace.php
diff --git a/includes/Extension/SearchReplace/Replace/class-file.php b/includes/extension/searchreplace/replace/class-file.php
similarity index 100%
rename from includes/Extension/SearchReplace/Replace/class-file.php
rename to includes/extension/searchreplace/replace/class-file.php
diff --git a/includes/Extension/SearchReplace/Replace/class-sql.php b/includes/extension/searchreplace/replace/class-sql.php
similarity index 97%
rename from includes/Extension/SearchReplace/Replace/class-sql.php
rename to includes/extension/searchreplace/replace/class-sql.php
index 085496a..94178b1 100644
--- a/includes/Extension/SearchReplace/Replace/class-sql.php
+++ b/includes/extension/searchreplace/replace/class-sql.php
@@ -8,9 +8,9 @@
 
 namespace StringLocator\Extension\SearchReplace\Replace;
 
+use StringLocator\Extension\SQL\Helpers;
 use StringLocator\Extension\SQL\Search;
 use StringLocator\String_Locator;
-use function StringLocator\Extension\SQL\validate_sql_fields;
 
 /**
  * SQL class.
@@ -60,13 +60,13 @@ public function __construct( $primary_column, $primary_key, $primary_type, $tabl
 	 * @return bool
 	 */
 	public function validate() {
-		if ( ! validate_sql_fields( $this->primary_column ) ) {
+		if ( ! Helpers::validate_sql_fields( $this->primary_column ) ) {
 			return false;
 		}
-		if ( ! validate_sql_fields( $this->table_name ) ) {
+		if ( ! Helpers::validate_sql_fields( $this->table_name ) ) {
 			return false;
 		}
-		if ( ! validate_sql_fields( $this->column_name ) ) {
+		if ( ! Helpers::validate_sql_fields( $this->column_name ) ) {
 			return false;
 		}
 
diff --git a/includes/Extension/SearchReplace/REST/class-replace.php b/includes/extension/searchreplace/rest/class-replace.php
similarity index 100%
rename from includes/Extension/SearchReplace/REST/class-replace.php
rename to includes/extension/searchreplace/rest/class-replace.php
diff --git a/includes/Extension/SearchReplace/template/error-notice.php b/includes/extension/searchreplace/template/error-notice.php
similarity index 100%
rename from includes/Extension/SearchReplace/template/error-notice.php
rename to includes/extension/searchreplace/template/error-notice.php
diff --git a/includes/Extension/SearchReplace/views/replace-form.php b/includes/extension/searchreplace/views/replace-form.php
similarity index 100%
rename from includes/Extension/SearchReplace/views/replace-form.php
rename to includes/extension/searchreplace/views/replace-form.php
diff --git a/includes/Extension/SQL/class-edit.php b/includes/extension/sql/class-edit.php
similarity index 90%
rename from includes/Extension/SQL/class-edit.php
rename to includes/extension/sql/class-edit.php
index 88e7cd9..4d650d3 100644
--- a/includes/Extension/SQL/class-edit.php
+++ b/includes/extension/sql/class-edit.php
@@ -5,6 +5,7 @@
 
 namespace StringLocator\Extension\SQL;
 
+use StringLocator\Extension\SQL\Helpers;
 use StringLocator\String_Locator;
 
 /**
@@ -74,12 +75,12 @@ public function sql_edit_page( $include_path ) {
 		}
 
 		// Validate the table name.
-		if ( ! isset( $_GET['sql-table'] ) || ! validate_sql_fields( $_GET['sql-table'] ) ) {
+		if ( ! isset( $_GET['sql-table'] ) || ! Helpers::validate_sql_fields( $_GET['sql-table'] ) ) {
 			return $include_path;
 		}
 
 		// Validate the primary column
-		if ( ! isset( $_GET['sql-primary-column'] ) || ! validate_sql_fields( $_GET['sql-primary-column'] ) ) {
+		if ( ! isset( $_GET['sql-primary-column'] ) || ! Helpers::validate_sql_fields( $_GET['sql-primary-column'] ) ) {
 			return $include_path;
 		}
 
diff --git a/includes/extension/sql/class-helpers.php b/includes/extension/sql/class-helpers.php
new file mode 100644
index 0000000..6b1f7d0
--- /dev/null
+++ b/includes/extension/sql/class-helpers.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace StringLocator\Extension\SQL;
+
+/**
+ * Helpers class.
+ */
+class Helpers {
+
+	public static function validate_sql_fields( $field ) {
+		return preg_match( '/^[0-9a-zA-Z_]+$/s', $field );
+	}
+
+}
+
diff --git a/includes/Extension/SQL/class-save.php b/includes/extension/sql/class-save.php
similarity index 100%
rename from includes/Extension/SQL/class-save.php
rename to includes/extension/sql/class-save.php
diff --git a/includes/Extension/SQL/class-search.php b/includes/extension/sql/class-search.php
similarity index 99%
rename from includes/Extension/SQL/class-search.php
rename to includes/extension/sql/class-search.php
index f7fd580..fe85f80 100644
--- a/includes/Extension/SQL/class-search.php
+++ b/includes/extension/sql/class-search.php
@@ -3,6 +3,7 @@
 namespace StringLocator\Extension\SQL;
 
 use StringLocator\Base\Search as SearchBase;
+use StringLocator\Extension\SQL\Helpers;
 use StringLocator\String_Locator;
 
 /**
@@ -214,7 +215,7 @@ public function run( $filenum ) {
 
 		$identifier_name = 'Tables_in_' . DB_NAME;
 
-		if ( ! validate_sql_fields( $identifier_name ) ) {
+		if ( ! Helpers::validate_sql_fields( $identifier_name ) ) {
 			wp_send_json_error(
 				array(
 					'continue' => false,
diff --git a/includes/Extension/SQL/Tests/class-serialized-data.php b/includes/extension/sql/tests/class-serialized-data.php
similarity index 99%
rename from includes/Extension/SQL/Tests/class-serialized-data.php
rename to includes/extension/sql/tests/class-serialized-data.php
index 4b2c5b5..b359d9f 100644
--- a/includes/Extension/SQL/Tests/class-serialized-data.php
+++ b/includes/extension/sql/tests/class-serialized-data.php
@@ -135,5 +135,3 @@ public function run( $content ) {
 		return true;
 	}
 }
-
-new Serialized_Data();
diff --git a/includes/Extension/SQL/views/editor/sql.php b/includes/extension/sql/views/editor/sql.php
similarity index 100%
rename from includes/Extension/SQL/views/editor/sql.php
rename to includes/extension/sql/views/editor/sql.php
diff --git a/includes/Extension/SQL/views/template/search.php b/includes/extension/sql/views/template/search.php
similarity index 100%
rename from includes/Extension/SQL/views/template/search.php
rename to includes/extension/sql/views/template/search.php
diff --git a/includes/REST/class-clean.php b/includes/rest/class-clean.php
similarity index 100%
rename from includes/REST/class-clean.php
rename to includes/rest/class-clean.php
diff --git a/includes/REST/class-directory-structure.php b/includes/rest/class-directory-structure.php
similarity index 100%
rename from includes/REST/class-directory-structure.php
rename to includes/rest/class-directory-structure.php
diff --git a/includes/REST/class-save.php b/includes/rest/class-save.php
similarity index 100%
rename from includes/REST/class-save.php
rename to includes/rest/class-save.php
diff --git a/includes/REST/class-search.php b/includes/rest/class-search.php
similarity index 100%
rename from includes/REST/class-search.php
rename to includes/rest/class-search.php
diff --git a/includes/Tests/class-loopback.php b/includes/tests/class-loopback.php
similarity index 100%
rename from includes/Tests/class-loopback.php
rename to includes/tests/class-loopback.php
diff --git a/includes/Tests/class-smart-scan.php b/includes/tests/class-smart-scan.php
similarity index 100%
rename from includes/Tests/class-smart-scan.php
rename to includes/tests/class-smart-scan.php
diff --git a/string-locator.php b/string-locator.php
index 236216e..a6e499c 100644
--- a/string-locator.php
+++ b/string-locator.php
@@ -28,6 +28,8 @@
 
 namespace StringLocator;
 
+use StringLocator\Extensions\SQL\Tests\Serialized_Data;
+
 if ( ! defined( 'ABSPATH' ) ) {
 	die();
 }
@@ -36,41 +38,11 @@
 define( 'STRING_LOCATOR_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
 define( 'STRING_LOCATOR_PLUGIN_FILE', __FILE__ );
 
-/**
- * Base classes that other classes may extend.
- */
-require_once __DIR__ . '/includes/Base/class-search.php';
-require_once __DIR__ . '/includes/Base/class-rest.php';
-
-/**
- * Search handlers
- */
-require_once __DIR__ . '/includes/Extension/SQL/sql.php';
-require_once __DIR__ . '/includes/Extension/SearchReplace/search-replace.php';
-
-/**
- * Plugin test runners
- */
-require_once __DIR__ . '/includes/Tests/class-loopback.php';
-require_once __DIR__ . '/includes/Tests/class-smart-scan.php';
+require __DIR__ . '/autoload.php';
 
-/**
- * Plugin action classes.
- */
-require_once __DIR__ . '/includes/class-save.php';
-require_once __DIR__ . '/includes/class-search.php';
-require_once __DIR__ . '/includes/class-directory-iterator.php';
-
-/**
- * Prepare REST endpoints.
- */
-require_once __DIR__ . '/includes/REST/class-save.php';
-require_once __DIR__ . '/includes/REST/class-clean.php';
-require_once __DIR__ . '/includes/REST/class-search.php';
-require_once __DIR__ . '/includes/REST/class-directory-structure.php';
+new Serialized_Data();
 
 /**
  * Instantiate the plugin
  */
-require_once __DIR__ . '/includes/class-string-locator.php';
 new String_Locator();