diff --git a/README.md b/README.md
index f8dd1d2..adea017 100644
--- a/README.md
+++ b/README.md
@@ -110,6 +110,29 @@ idGenerator: (request) => {
 }
 ```
 
+##### idStore
+A session id store. Used to store and retrieve session ids.
+* get(request, key): string | undefined
+* set(reply, key, value, cookieOptions)
+* clear(reply, key, cookieOptions)
+
+Defaults to a cookie store.
+  
+Custom implementation example:
+```js
+idStore: {
+    get: (request, key) => request.headers[key.toLowerCase()],
+    set: (reply, key, value) => {
+      reply.header(key, value);
+    },
+    clear: (reply, key) => {
+      reply.removeHeader(key);
+    },
+  },
+}
+```
+
+
 #### request.session
 
 Allows to access or modify the session data.
diff --git a/lib/fastifySession.js b/lib/fastifySession.js
index 56aa6f4..f288aab 100644
--- a/lib/fastifySession.js
+++ b/lib/fastifySession.js
@@ -4,6 +4,7 @@ const fp = require('fastify-plugin')
 const idGenerator = require('./idGenerator')()
 const Store = require('./store')
 const Session = require('./session')
+const idStore = require('./idStore')
 
 function fastifySession (fastify, options, next) {
   const error = checkOptions(options)
@@ -14,6 +15,7 @@ function fastifySession (fastify, options, next) {
   options = ensureDefaults(options)
 
   const sessionStore = options.store
+  const sessionIdStore = options.idStore
   const cookieSigner = options.signer
   const cookieName = options.cookieName
   const cookiePrefix = options.cookiePrefix
@@ -113,14 +115,14 @@ function fastifySession (fastify, options, next) {
 
   const getCookieSessionId = hasCookiePrefix
     ? function getCookieSessionId (request) {
-      const cookieValue = request.cookies[cookieName]
+      const cookieValue = sessionIdStore.get(request, cookieName)
       return (
         cookieValue?.startsWith(cookiePrefix) &&
         cookieValue.slice(cookiePrefixLength)
       )
     }
     : function getCookieSessionId (request) {
-      return request.cookies[cookieName]
+      return sessionIdStore.get(request, cookieName)
     }
 
   function onRequest (options) {
@@ -171,11 +173,12 @@ function fastifySession (fastify, options, next) {
       if (!saveSession || isInsecureConnection) {
         // if a session cookie is set, but has a different ID, clear it
         if (cookieSessionId && cookieSessionId !== session.encryptedSessionId) {
-          reply.clearCookie(cookieName, { domain: cookieOpts.domain })
+          sessionIdStore.clear?.(reply, cookieName, { domain: cookieOpts.domain })
         }
 
         if (session.isSaved()) {
-          reply.setCookie(
+          sessionIdStore.set?.(
+            reply,
             cookieName,
             sessionIdWithPrefix,
             // we need to remove extra properties to align the same with `express-session`
@@ -192,7 +195,8 @@ function fastifySession (fastify, options, next) {
           done(err)
           return
         }
-        reply.setCookie(
+        sessionIdStore.set?.(
+          reply,
           cookieName,
           sessionIdWithPrefix,
           // we need to remove extra properties to align the same with `express-session`
@@ -220,6 +224,7 @@ function fastifySession (fastify, options, next) {
   function ensureDefaults (options) {
     const opts = {}
     opts.store = options.store || new Store()
+    opts.idStore = options.idStore || idStore
     opts.idGenerator = options.idGenerator || idGenerator
     opts.cookieName = options.cookieName || 'sessionId'
     opts.cookie = options.cookie || {}
diff --git a/lib/idStore.js b/lib/idStore.js
new file mode 100644
index 0000000..f975bcf
--- /dev/null
+++ b/lib/idStore.js
@@ -0,0 +1,5 @@
+module.exports = {
+  get: (request, key) => request.cookies[key],
+  set: (reply, key, value, opts) => reply.setCookie(key, value, opts),
+  clear: (reply, key, opts) => reply.clearCookie(key, opts)
+}
diff --git a/test/customIdStore.test.js b/test/customIdStore.test.js
new file mode 100644
index 0000000..87f43aa
--- /dev/null
+++ b/test/customIdStore.test.js
@@ -0,0 +1,73 @@
+'use strict'
+
+const test = require('node:test')
+const Fastify = require('fastify')
+const fastifyCookie = require('@fastify/cookie')
+const fastifySession = require('../lib/fastifySession')
+const { DEFAULT_OPTIONS, DEFAULT_SESSION_ID, DEFAULT_ENCRYPTED_SESSION_ID } = require('./util')
+
+const idStore = {
+  get: (request, key) => request.headers[key.toLowerCase()],
+  set: (reply, key, value) => reply.header(key, value),
+  clear: (reply, key) => reply.removeHeader(key)
+}
+
+test('should set sessionid header with custom id store', async (t) => {
+  t.plan(3)
+  const fastify = Fastify()
+  let sessionId = null
+
+  fastify.addHook('onRequest', async (request) => {
+    request.raw.socket.encrypted = true
+  })
+  fastify.register(fastifyCookie)
+  fastify.register(fastifySession, {
+    ...DEFAULT_OPTIONS,
+    idStore
+  })
+  fastify.get('/', (request, reply) => {
+    request.session.test = {}
+    sessionId = request.session.sessionId
+    reply.send(200)
+  })
+  await fastify.listen({ port: 0 })
+  t.after(() => { fastify.close() })
+
+  const response = await fastify.inject({
+    url: '/'
+  })
+
+  t.assert.strictEqual(response.statusCode, 200)
+  t.assert.ok(sessionId)
+  const pattern = `${sessionId}\\..{43,57}`
+  t.assert.strictEqual(new RegExp(pattern).test(response.headers['sessionid']), true)
+})
+
+test('should retrieve sessionid header with custom id store', async (t) => {
+  t.plan(2)
+  const fastify = Fastify()
+
+  fastify.register(fastifyCookie)
+  fastify.register(fastifySession, {
+    ...DEFAULT_OPTIONS,
+    idStore,
+    store: {
+      get (id, cb) { cb(null, { id }) },
+    }
+  })
+  fastify.get('/', (request, reply) => {
+    t.assert.strictEqual(request.session.sessionId, DEFAULT_SESSION_ID)
+    reply.send(200)
+  })
+  await fastify.listen({ port: 0 })
+  t.after(() => { fastify.close() })
+
+  const response = await fastify.inject({
+    url: '/',
+    headers: {
+      sessionid: DEFAULT_ENCRYPTED_SESSION_ID
+    }
+  })
+
+  t.assert.strictEqual(response.statusCode, 200)
+})
diff --git a/types/types.d.ts b/types/types.d.ts
index e0dcd0d..caecc8c 100644
--- a/types/types.d.ts
+++ b/types/types.d.ts
@@ -155,6 +155,12 @@ declare namespace fastifySession {
      */
     store?: fastifySession.SessionStore;
 
+    /**
+     * A session ID store.
+     * Defaults to a cookie based store.
+     */
+    idStore?: SessionIdStore;
+
     /**
      * Save sessions to the store, even when they are new and not modified.
      * Defaults to true. Setting this to false can be useful to save storage space and to comply with the EU cookie law.
@@ -182,6 +188,12 @@ declare namespace fastifySession {
     maxAge?: number;
   }
 
+  export interface SessionIdStore {
+    get: (request: Fastify.FastifyRequest, key: string) => string | undefined;
+    set?: (reply: Fastify.FastifyReply, key: string, value: string, cookieOptions: CookieOptions) => void;
+    clear?: (reply: Fastify.FastifyReply, key: string, cookieOptions: CookieOptions) => void;
+  }
+
   export class MemoryStore implements fastifySession.SessionStore {
     constructor (map?: Map<string, Fastify.Session>)
     set (