diff --git a/api/package.json b/api/package.json
index c49bf3b99ff..d275586105f 100644
--- a/api/package.json
+++ b/api/package.json
@@ -5,8 +5,8 @@
   },
   "dependencies": {
     "@fastify/cookie": "^8.3.0",
-    "@fastify/middie": "8.3",
     "@fastify/csrf-protection": "6.3.0",
+    "@fastify/middie": "8.3",
     "@fastify/session": "^10.1.1",
     "@fastify/swagger": "^8.3.1",
     "@fastify/swagger-ui": "^1.5.0",
@@ -17,7 +17,8 @@
     "fastify": "4.17.0",
     "fastify-auth0-verify": "^1.0.0",
     "fastify-plugin": "^4.3.0",
-    "nodemon": "2.0.22"
+    "nodemon": "2.0.22",
+    "query-string": "^7.1.3"
   },
   "description": "The freeCodeCamp.org open-source codebase and curriculum",
   "devDependencies": {
diff --git a/api/src/plugins/redirect-with-message.test.ts b/api/src/plugins/redirect-with-message.test.ts
new file mode 100644
index 00000000000..5a9e52f54b7
--- /dev/null
+++ b/api/src/plugins/redirect-with-message.test.ts
@@ -0,0 +1,101 @@
+import Fastify, { FastifyInstance } from 'fastify';
+import qs from 'query-string';
+
+import redirectWithMessage from './redirect-with-message';
+
+async function setupServer() {
+  const fastify = Fastify();
+  await fastify.register(redirectWithMessage);
+  return fastify;
+}
+
+const isString = (value: unknown): value is string => {
+  return typeof value === 'string';
+};
+
+describe('redirectWithMessage plugin', () => {
+  it('should decorate reply object with redirectWithMessage method', async () => {
+    expect.assertions(3);
+
+    const fastify = await setupServer();
+
+    fastify.get('/', (_req, reply) => {
+      expect(reply).toHaveProperty('redirectWithMessage');
+      expect(reply.redirectWithMessage).toBeInstanceOf(Function);
+      return { foo: 'bar' };
+    });
+
+    const res = await fastify.inject({
+      method: 'GET',
+      url: '/'
+    });
+
+    expect(res.statusCode).toEqual(200);
+  });
+
+  describe('redirectWithMessage method', () => {
+    let fastify: FastifyInstance;
+    beforeEach(async () => {
+      fastify = await setupServer();
+    });
+
+    it('should redirect to the first argument', async () => {
+      fastify.get('/', (_req, reply) => {
+        return reply.redirectWithMessage('/target', {
+          type: 'info',
+          content: 'foo'
+        });
+      });
+      const res = await fastify.inject({
+        method: 'GET',
+        url: '/'
+      });
+
+      expect(res.headers.location).toMatch(/^\/target/);
+      expect(res.statusCode).toEqual(302);
+    });
+
+    it('should convert the second argument into a query string', async () => {
+      fastify.get('/', (_req, reply) => {
+        return reply.redirectWithMessage('/target', {
+          type: 'info',
+          content: 'foo'
+        });
+      });
+      const res = await fastify.inject({
+        method: 'GET',
+        url: '/'
+      });
+
+      expect(res.headers.location).toMatch(/^\/target\?messages=info/);
+    });
+
+    it('should encode the message twice when creating the query string', async () => {
+      const expectedMessage = { danger: ['foo bar'] };
+
+      fastify.get('/', (_req, reply) => {
+        return reply.redirectWithMessage('/target', {
+          type: 'danger',
+          content: 'foo bar'
+        });
+      });
+
+      const res = await fastify.inject({
+        method: 'GET',
+        url: '/'
+      });
+      if (!isString(res.headers.location))
+        throw new Error('Location is not a string');
+      const { search } = new URL(res.headers.location, 'http://localhost');
+
+      // The query string itself is encoded:
+      const { messages } = qs.parse(search, { arrayFormat: 'index' });
+      if (!isString(messages)) throw new Error('Messages is not a string');
+
+      // As is the message embedded in it:
+      expect(qs.parse(messages, { arrayFormat: 'index' })).toEqual(
+        expectedMessage
+      );
+    });
+  });
+});
diff --git a/api/src/plugins/redirect-with-message.ts b/api/src/plugins/redirect-with-message.ts
new file mode 100644
index 00000000000..3fc0ca21242
--- /dev/null
+++ b/api/src/plugins/redirect-with-message.ts
@@ -0,0 +1,54 @@
+import { FastifyPluginCallback, type FastifyReply } from 'fastify';
+import fp from 'fastify-plugin';
+// TODO: (POST MVP)use node's querystring and just JSON stringify the message.
+// No need for query-string on either side.
+
+import qs from 'query-string';
+
+declare module 'fastify' {
+  interface FastifyReply {
+    redirectWithMessage: typeof redirectWithMessage;
+  }
+}
+
+type Message = {
+  type: 'info' | 'danger' | 'success' | 'errors';
+  content: string;
+};
+
+type MessageQuery = {
+  info?: string[];
+  danger?: string[];
+  success?: string[];
+  errors?: string[];
+};
+
+// The client expects a message like { info: ['foo'] }, { danger: ['bar'] } etc.
+const prepareMessage = (message: Message): MessageQuery => ({
+  [message.type]: [message.content]
+});
+
+function redirectWithMessage(
+  this: FastifyReply,
+  url: string,
+  message: Message
+) {
+  return this.redirect(
+    `${url}?${qs.stringify(
+      {
+        messages: qs.stringify(prepareMessage(message), {
+          arrayFormat: 'index'
+        })
+      },
+      { arrayFormat: 'index' }
+    )}`
+  );
+}
+
+const plugin: FastifyPluginCallback = (fastify, _options, done) => {
+  fastify.decorateReply('redirectWithMessage', redirectWithMessage);
+
+  done();
+};
+
+export default fp(plugin);
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index e1fb5ff4d43..52f1c1f1a1b 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -213,6 +213,9 @@ importers:
       nodemon:
         specifier: 2.0.22
         version: 2.0.22
+      query-string:
+        specifier: ^7.1.3
+        version: 7.1.3
     devDependencies:
       '@fastify/type-provider-typebox':
         specifier: 3.2.0