diff --git a/src/common.d.ts b/src/common.d.ts
new file mode 100644
index 0000000..eee4e97
--- /dev/null
+++ b/src/common.d.ts
@@ -0,0 +1,7 @@
+// Similar to `global.d.ts` but with import/export
+import { Dispatch, SetStateAction } from 'react'
+
+type ReactIO<T> = {
+  value: T
+  onChange: Dispatch<SetStateAction<T>>
+}
diff --git a/src/components/Gitako.tsx b/src/components/Gitako.tsx
index 8fc22db..a119218 100644
--- a/src/components/Gitako.tsx
+++ b/src/components/Gitako.tsx
@@ -1,6 +1,7 @@
 import { SideBar } from 'components/SideBar'
 import { ConfigsContextWrapper } from 'containers/ConfigsContext'
 import { ReloadContextWrapper } from 'containers/ReloadContext'
+import { InspectorContextWrapper } from 'containers/StateInspector'
 import * as React from 'react'
 import { ErrorBoundary } from '../containers/ErrorBoundary'
 import { StateBarErrorContextWrapper } from '../containers/ErrorContext'
@@ -10,20 +11,22 @@ import { StateBarStateContextWrapper } from '../containers/SideBarState'
 
 export function Gitako() {
   return (
-    <ReloadContextWrapper>
-      <ErrorBoundary>
-        <ConfigsContextWrapper>
-          <StateBarStateContextWrapper>
-            <StateBarErrorContextWrapper>
-              <OAuthWrapper>
-                <RepoContextWrapper>
-                  <SideBar />
-                </RepoContextWrapper>
-              </OAuthWrapper>
-            </StateBarErrorContextWrapper>
-          </StateBarStateContextWrapper>
-        </ConfigsContextWrapper>
-      </ErrorBoundary>
-    </ReloadContextWrapper>
+    <InspectorContextWrapper>
+      <ReloadContextWrapper>
+        <ErrorBoundary>
+          <ConfigsContextWrapper>
+            <StateBarStateContextWrapper>
+              <StateBarErrorContextWrapper>
+                <OAuthWrapper>
+                  <RepoContextWrapper>
+                    <SideBar />
+                  </RepoContextWrapper>
+                </OAuthWrapper>
+              </StateBarErrorContextWrapper>
+            </StateBarStateContextWrapper>
+          </ConfigsContextWrapper>
+        </ErrorBoundary>
+      </ReloadContextWrapper>
+    </InspectorContextWrapper>
   )
 }
diff --git a/src/containers/ErrorContext.tsx b/src/containers/ErrorContext.tsx
index 53d9455..01c3c7a 100644
--- a/src/containers/ErrorContext.tsx
+++ b/src/containers/ErrorContext.tsx
@@ -1,3 +1,4 @@
+import { useInspector } from 'containers/StateInspector'
 import * as React from 'react'
 import { useStateIO } from 'utils/hooks/useStateIO'
 
@@ -7,6 +8,7 @@ export const SideBarErrorContext = React.createContext<SideBarErrorContextShape
 
 export function StateBarErrorContextWrapper({ children }: React.PropsWithChildren<{}>) {
   const $error = useStateIO<string | null>(null)
+  useInspector('SideBarErrorContext', $error.value)
 
   return <SideBarErrorContext.Provider value={$error}>{children}</SideBarErrorContext.Provider>
 }
diff --git a/src/containers/SideBarState.tsx b/src/containers/SideBarState.tsx
index 815a122..8b1ba9d 100644
--- a/src/containers/SideBarState.tsx
+++ b/src/containers/SideBarState.tsx
@@ -1,5 +1,6 @@
 import * as React from 'react'
 import { useStateIO } from 'utils/hooks/useStateIO'
+import { useInspector } from './StateInspector'
 
 export type SideBarState =
   | 'disabled'
@@ -19,6 +20,7 @@ export const SideBarStateContext = React.createContext<SideBarStateContextShape
 
 export function StateBarStateContextWrapper({ children }: React.PropsWithChildren<{}>) {
   const $state = useStateIO<SideBarState>('disabled')
+  useInspector('SideBarStateContext', $state.value)
 
   return (
     <SideBarStateContext.Provider value={$state}>
diff --git a/src/containers/StateInspector.tsx b/src/containers/StateInspector.tsx
new file mode 100644
index 0000000..3591642
--- /dev/null
+++ b/src/containers/StateInspector.tsx
@@ -0,0 +1,58 @@
+import { ReactIO } from 'common'
+import { IN_PRODUCTION_MODE } from 'env'
+import * as React from 'react'
+import { useStateIO } from 'utils/hooks/useStateIO'
+
+export type InspectorContextShape = ReactIO<JSONObject>
+
+export const InspectorContext = React.createContext<InspectorContextShape | null>(null)
+
+export const InspectorContextWrapper = IN_PRODUCTION_MODE
+  ? React.Fragment
+  : function InspectorContextWrapper({ children }: React.PropsWithChildren<{}>) {
+      const $ = useStateIO<JSONObject>({})
+      const [show, setShow] = React.useState(true)
+
+      return (
+        <InspectorContext.Provider value={$}>
+          {show ? (
+            <div
+              style={{
+                position: 'fixed',
+                top: '0',
+                right: '0',
+                height: '100vh',
+                width: '360px',
+                overflow: 'auto',
+                background: 'rgba(255, 255, 255, 0.75)',
+                display: 'flex',
+                flexDirection: 'column',
+              }}
+            >
+              <pre style={{ flex: 1 }}>{JSON.stringify($.value, null, 2)}</pre>
+              <div>
+                <button onClick={() => setShow(false)}>❌</button>
+              </div>
+            </div>
+          ) : (
+            <div
+              style={{
+                position: 'fixed',
+                bottom: '0',
+                right: '0',
+              }}
+            >
+              <button onClick={() => setShow(true)}>🔎</button>
+            </div>
+          )}
+          {children}
+        </InspectorContext.Provider>
+      )
+    }
+
+export function useInspector(key: string, value: JSONValue) {
+  const $ = React.useContext(InspectorContext)
+  React.useEffect(() => {
+    $?.onChange(prev => ({ ...prev, [key]: value }))
+  }, [key, value]) // eslint-disable-line react-hooks/exhaustive-deps
+}