diff --git a/project.clj b/project.clj
index 6c4926db..f843d35e 100644
--- a/project.clj
+++ b/project.clj
@@ -26,6 +26,9 @@
                                   [metosin/spec-tools "0.3.3"]
                                   [org.clojure/spec.alpha "0.1.123"]
 
+                                  [expound "0.2.1"]
+                                  [orchestra "2017.08.13"]
+
                                   [criterium "0.4.4"]
                                   [org.clojure/test.check "0.9.0"]
                                   [org.clojure/tools.namespace "0.2.11"]
diff --git a/src/reitit/core.cljc b/src/reitit/core.cljc
index ae1282fb..bd1aa9da 100644
--- a/src/reitit/core.cljc
+++ b/src/reitit/core.cljc
@@ -30,7 +30,7 @@
   (expand [_ _]))
 
 (defn walk [data {:keys [path meta routes expand]
-                  :or {path "", meta [], routes [], expand expand}
+                  :or {meta [], routes [], expand expand}
                   :as opts}]
   (letfn
     [(walk-many [p m r]
@@ -100,6 +100,9 @@
   (match-by-path [this path])
   (match-by-name [this name] [this name params]))
 
+(defn router? [x]
+  (satisfies? Router x))
+
 (defrecord Match [template meta result params path])
 (defrecord PartialMatch [template meta result params required])
 
@@ -242,7 +245,7 @@
 
   | key          | description |
   | -------------|-------------|
-  | `:path`      | Base-path for routes (default `\"\"`)
+  | `:path`      | Base-path for routes
   | `:routes`    | Initial resolved routes (default `[]`)
   | `:meta`      | Initial route meta (default `{}`)
   | `:expand`    | Function of `arg opts => meta` to expand route arg to route meta-data (default `reitit.core/expand`)
diff --git a/src/reitit/spec.cljc b/src/reitit/spec.cljc
new file mode 100644
index 00000000..8953f3f7
--- /dev/null
+++ b/src/reitit/spec.cljc
@@ -0,0 +1,63 @@
+(ns reitit.spec
+  (:require [clojure.spec.alpha :as s]
+            [clojure.spec.gen.alpha :as gen]
+            [clojure.string :as str]
+            [reitit.core :as reitit]))
+
+;;
+;; routes
+;;
+
+(s/def ::path (s/with-gen (s/and string? #(str/starts-with? % "/"))
+                          #(gen/fmap (fn [s] (str "/" s)) (s/gen string?))))
+
+(s/def ::arg (s/and any? (complement vector?)))
+(s/def ::meta (s/map-of keyword? any?))
+(s/def ::result any?)
+
+(s/def ::raw-route
+  (s/cat :path ::path
+         :arg (s/? ::arg)
+         :childs (s/* (s/and ::raw-route))))
+
+(s/def ::raw-routes
+  (s/or :route ::raw-route
+        :routes (s/coll-of ::raw-route :into [])))
+
+(s/def ::route
+  (s/cat :path ::path
+         :meta ::meta))
+
+(s/def ::routes
+  (s/or :route ::route
+        :routes (s/coll-of ::route :into [])))
+
+;;
+;; router
+;;
+
+(s/def ::router reitit/router?)
+(s/def :reitit.router/path ::path)
+(s/def :reitit.router/routes ::routes)
+(s/def :reitit.router/meta ::meta)
+(s/def :reitit.router/expand fn?)
+(s/def :reitit.router/coerce fn?)
+(s/def :reitit.router/compile fn?)
+(s/def :reitit.router/conflicts fn?)
+(s/def :reitit.router/router fn?)
+
+(s/def ::opts
+  (s/nilable
+    (s/keys :opt-un [:reitit.router/path
+                     :reitit.router/routes
+                     :reitit.router/meta
+                     :reitit.router/expand
+                     :reitit.router/coerce
+                     :reitit.router/compile
+                     :reitit.router/conflicts
+                     :reitit.router/router])))
+
+(s/fdef reitit/router
+        :args (s/or :1arity (s/cat :data (s/spec ::raw-routes))
+                    :2arity (s/cat :data (s/spec ::raw-routes), :opts ::opts))
+        :ret ::router)
diff --git a/test/cljc/reitit/spec_test.cljc b/test/cljc/reitit/spec_test.cljc
new file mode 100644
index 00000000..cb3f18a6
--- /dev/null
+++ b/test/cljc/reitit/spec_test.cljc
@@ -0,0 +1,74 @@
+(ns reitit.spec-test
+  (:require [clojure.test :refer [deftest testing is are]]
+            [clojure.spec.test.alpha :as stest]
+            [clojure.spec.alpha :as s]
+            [reitit.core :as reitit]
+            [reitit.spec :as spec])
+  #?(:clj
+     (:import (clojure.lang ExceptionInfo))))
+
+(stest/instrument `reitit/router)
+
+(deftest router-spec-test
+
+  (testing "router"
+
+    (testing "route-data"
+      (are [data]
+        (is (= true (reitit/router? (reitit/router data))))
+
+        ["/api" {}]
+
+        [["/api" {}]]
+
+        ["/api"
+         ["/ipa" ::ipa]
+         ["/tea"
+          ["/room"]]])
+
+      (testing "with invalid routes"
+        (are [data]
+          (is (thrown-with-msg?
+                ExceptionInfo
+                #"Call to #'reitit.core/router did not conform to spec"
+                (reitit/router
+                  data)))
+
+          ;; missing slash
+          ["invalid" {}]
+
+          ;; path
+          [:invalid {}]
+
+          ;; vector meta
+          ["/api" []
+           ["/ipa"]])))
+
+    (testing "options"
+
+      (are [opts]
+        (is (= true (reitit/router? (reitit/router ["/api"] opts))))
+
+        {:path "/"}
+        {:meta {}}
+        {:expand (fn [_ _] {})}
+        {:coerce (fn [route _] route)}
+        {:compile (fn [_ _])}
+        {:conflicts (fn [_])}
+        {:router reitit/linear-router})
+
+      (are [opts]
+        (is (thrown-with-msg?
+              ExceptionInfo
+              #"Call to #'reitit.core/router did not conform to spec"
+              (reitit/router
+                ["/api"] opts)))
+
+        {:path ""}
+        {:path nil}
+        {:meta nil}
+        {:expand nil}
+        {:coerce nil}
+        {:compile nil}
+        {:conflicts nil}
+        {:router nil}))))