diff --git a/server/src/api/controllers/authController.js b/server/src/api/controllers/authController.js
index 0c18c81..62802d0 100644
--- a/server/src/api/controllers/authController.js
+++ b/server/src/api/controllers/authController.js
@@ -1,5 +1,10 @@
 import User from '../../models/user.js'
-import { genJWT, hashPassword } from '../../utils/auth.js'
+import {
+  genJWT,
+  hashPassword,
+  isValidEmail,
+  isValidUsername,
+} from '../../utils/auth.js'
 
 export async function issueToken(req, res) {
   const { user } = req
@@ -13,16 +18,37 @@ export async function issueToken(req, res) {
 
 export async function checkUsername(req, res) {
   const { username } = req.query
-  const exists = await User.exists({ username })
-  if (exists) {
-    res.status(409).json({
-      message: `"${username}" already exists`,
-    })
-  } else {
+  if (isValidEmail(username)) {
+    if (await User.exists({ email: username })) {
+      res.status(409).json({
+        type: 'email',
+        message: `"${username}" already exists`,
+      })
+      return
+    }
     res.status(200).json({
+      type: 'email',
       message: `"${username}" is available`,
     })
+    return
   }
+  if (isValidUsername(username)) {
+    if (await User.exists({ username })) {
+      res.status(409).json({
+        type: 'username',
+        message: `"${username}" already exists`,
+      })
+      return
+    }
+    res.status(200).json({
+      type: 'username',
+      message: `"${username}" is available`,
+    })
+    return
+  }
+  res.status(400).json({
+    message: 'invalid username or email',
+  })
 }
 
 export async function register(req, res, next) {
diff --git a/server/src/utils/auth.js b/server/src/utils/auth.js
index 9199286..fde5770 100644
--- a/server/src/utils/auth.js
+++ b/server/src/utils/auth.js
@@ -8,29 +8,17 @@ export function hashPassword(password) {
 }
 
 export async function createTestUser() {
-  let user = await User.findOne({ username: 'testUser' })
+  let user = await User.findOne({ username: 'alex' })
   if (!user) {
     user = new User({
-      username: 'testUser',
-      email: 'test@example.com',
+      username: 'alex',
+      email: 'alex@example.com',
     })
-    user.hashedPassword = await hashPassword('testPassword')
+    user.hashedPassword = await hashPassword('123456')
     await user.save()
   }
 }
 
-export async function defaultUser() {
-  let user = await User.findOne({ username: 'defaultUser' })
-  if (!user) {
-    user = new User({
-      username: 'defaultUser',
-      email: 'jackson@example.com',
-    })
-    await user.save()
-  }
-  return user
-}
-
 export function genJWT(payload) {
   return new Promise((resolve, reject) => {
     jwt.sign(