diff --git a/src/Filter/FilterInterface.php b/src/Filter/FilterInterface.php
new file mode 100644
index 000000000..87cd60cf9
--- /dev/null
+++ b/src/Filter/FilterInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Filter;
+
+interface FilterInterface
+{
+    /**
+     * This filter will only be run when a query contains a filter param with this key.
+     */
+    public function getKey(): string;
+
+    /**
+     * Filters a query.
+     *
+     * @param WrappedFilter $filter
+     * @param string $value The value of the requested filter
+     */
+    public function apply(WrappedFilter $wrappedFilter, $filterValue);
+}