diff --git a/src/lib/__tests__/stateCookie.test.ts b/src/lib/__tests__/stateCookie.test.ts
new file mode 100644
index 0000000..1104ebb
--- /dev/null
+++ b/src/lib/__tests__/stateCookie.test.ts
@@ -0,0 +1,36 @@
+import { describe, test, expect } from "vitest"
+import { getStateCookie, setStateCookie } from "../stateCookie"
+
+describe("setStateCookie", () => {
+  test("throws errors on empty string", () => {
+    expect(() => setStateCookie(""))
+      .toThrow("state value is required")
+  })
+  test("sets cookie with prefix app.txs", () => {
+    const state = setStateCookie("code_verifier_secret")
+    expect(document.cookie)
+      .toMatch(`app.txs.${state}=code_verifier_secret`)
+  })
+  test("sets cookie with latest value", () => {
+    const state = setStateCookie("code_verifier_secret")
+    expect(document.cookie)
+      .toMatch(`app.txs.${state}=code_verifier_secret`)
+  })
+  test("returns state", () => {
+    const state = setStateCookie("code_verifier_secret")
+    expect(state).toMatch(/[\w-]+/)
+  })
+})
+
+describe("getStateCookie", () => {
+  test("gets cookie", () => {
+    const state = crypto.randomUUID()
+    const random = Math.random().toString(36).substring(7)
+    document.cookie = `app.txs.${state}=${random}`
+    expect(getStateCookie(state)).toBe(random)
+  })
+
+  test("gets none", () => {
+    expect(getStateCookie('nothere')).toBeUndefined()
+  })
+})
diff --git a/src/lib/stateCookie.ts b/src/lib/stateCookie.ts
new file mode 100644
index 0000000..846db16
--- /dev/null
+++ b/src/lib/stateCookie.ts
@@ -0,0 +1,15 @@
+
+import { saveCookie, getCookie } from './cookie'
+
+export const setStateCookie = (value: string) => {
+  if (!value) throw new Error('state value is required')
+
+  const state = crypto.randomUUID()
+  saveCookie(`app.txs.${state}`, value, 30)
+
+  return state
+}
+
+export const getStateCookie = (state: string) => {
+  return getCookie(`app.txs.${state}`)
+}