diff --git a/api/pom.xml b/api/pom.xml
index 40e5d0b..3df2ab1 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -160,6 +160,11 @@
             <artifactId>hoplite-yaml</artifactId>
             <version>${hoplite_version}</version>
         </dependency>
+        <dependency>
+            <groupId>am.ik.yavi</groupId>
+            <artifactId>yavi</artifactId>
+            <version>0.4.0</version>
+        </dependency>
         <dependency>
             <groupId>com.github.javafaker</groupId>
             <artifactId>javafaker</artifactId>
diff --git a/api/src/features/ErrorFeature.kt b/api/src/features/ErrorFeature.kt
index c901e7e..ee59c87 100644
--- a/api/src/features/ErrorFeature.kt
+++ b/api/src/features/ErrorFeature.kt
@@ -1,5 +1,7 @@
 package be.vandewalleh.features
 
+import am.ik.yavi.core.ViolationDetail
+import be.vandewalleh.validation.ValidationException
 import io.ktor.application.*
 import io.ktor.features.*
 import io.ktor.http.*
@@ -11,5 +13,13 @@ fun Application.handleErrors() {
         exception<IOException> {
             call.respond(HttpStatusCode.BadRequest)
         }
+        exception<ValidationException> {
+            val error = ViolationError(it.details[0])
+            call.respond(HttpStatusCode.BadRequest, error)
+        }
     }
-}
\ No newline at end of file
+}
+
+class ViolationError(detail: ViolationDetail) {
+    val msg = detail.defaultMessage
+}
diff --git a/api/src/routing/UserController.kt b/api/src/routing/UserController.kt
index bbdbea9..4205f85 100644
--- a/api/src/routing/UserController.kt
+++ b/api/src/routing/UserController.kt
@@ -4,6 +4,8 @@ import be.vandewalleh.entities.User
 import be.vandewalleh.extensions.respondStatus
 import be.vandewalleh.extensions.userId
 import be.vandewalleh.services.UserService
+import be.vandewalleh.validation.receiveValidated
+import be.vandewalleh.validation.user.registerValidator
 import io.ktor.application.*
 import io.ktor.auth.*
 import io.ktor.http.*
@@ -18,14 +20,9 @@ import java.time.LocalDateTime
 fun Routing.user(kodein: Kodein) {
     val userService by kodein.instance<UserService>()
 
-    post("/user/test") {
-        val user = call.receive<User>()
-        call.respond(user)
-    }
-
     route("/user") {
         post {
-            val user = call.receive<User>()
+            val user = call.receiveValidated(registerValidator)
 
             if (userService.userExists(user.username, user.email))
                 return@post call.respondStatus(HttpStatusCode.Conflict)
@@ -39,7 +36,7 @@ fun Routing.user(kodein: Kodein) {
 
         authenticate {
             put {
-                val user = call.receive<User>()
+                val user = call.receiveValidated(registerValidator)
 
                 if (userService.userExists(user.username, user.email))
                     return@put call.respond(HttpStatusCode.Conflict)
diff --git a/api/src/validation/ValidationExtensions.kt b/api/src/validation/ValidationExtensions.kt
new file mode 100644
index 0000000..1d00401
--- /dev/null
+++ b/api/src/validation/ValidationExtensions.kt
@@ -0,0 +1,14 @@
+package be.vandewalleh.validation
+
+import am.ik.yavi.core.Validator
+import am.ik.yavi.core.ViolationDetail
+import io.ktor.application.*
+import io.ktor.request.*
+
+suspend inline fun <reified T : Any> ApplicationCall.receiveValidated(validator: Validator<T>): T {
+    val value: T = receive()
+    validator.validate(value).throwIfInvalid { ValidationException(it.details()) }
+    return value
+}
+
+data class ValidationException(val details: List<ViolationDetail>) : RuntimeException()
diff --git a/api/src/validation/user/UserValidation.kt b/api/src/validation/user/UserValidation.kt
new file mode 100644
index 0000000..6f2063e
--- /dev/null
+++ b/api/src/validation/user/UserValidation.kt
@@ -0,0 +1,18 @@
+package be.vandewalleh.validation.user
+
+import am.ik.yavi.builder.ValidatorBuilder
+import am.ik.yavi.builder.konstraint
+import am.ik.yavi.core.Validator
+import be.vandewalleh.entities.User
+
+val registerValidator: Validator<User> = ValidatorBuilder.of<User>()
+    .konstraint(User::username) {
+        notNull().lessThanOrEqual(50).greaterThanOrEqual(3)
+    }
+    .konstraint(User::email) {
+        notNull().notEmpty().lessThanOrEqual(255).email()
+    }
+    .konstraint(User::password) {
+        notNull().greaterThanOrEqual(6)
+    }
+    .build()
diff --git a/api/test/routing/UserControllerKtTest.kt b/api/test/integration/routing/UserControllerKtTest.kt
similarity index 95%
rename from api/test/routing/UserControllerKtTest.kt
rename to api/test/integration/routing/UserControllerKtTest.kt
index 8e521fc..04fe9d1 100644
--- a/api/test/routing/UserControllerKtTest.kt
+++ b/api/test/integration/routing/UserControllerKtTest.kt
@@ -1,4 +1,4 @@
-package routing
+package integration.routing
 
 import be.vandewalleh.auth.SimpleJWT
 import be.vandewalleh.entities.User
@@ -70,7 +70,7 @@ class UserControllerKtTest {
             val res = testEngine.post("/user") {
                 json {
                     it["username"] = "new"
-                    it["password"] = "test"
+                    it["password"] = "test123abc"
                     it["email"] = "new@test.com"
                 }
             }
@@ -84,7 +84,7 @@ class UserControllerKtTest {
                 json {
                     it["username"] = "existing"
                     it["email"] = "existing@test.com"
-                    it["password"] = "test"
+                    it["password"] = "test123abc"
                 }
             }
             res.status() `should be equal to` HttpStatusCode.Conflict
@@ -129,6 +129,7 @@ class UserControllerKtTest {
                 json {
                     it["username"] = "ThisIsMyNewName"
                     it["email"] = "ThisIsMyNewName@mail.com"
+                    it["password"] = "ThisIsMyCurrentPassword"
                 }
             }
 
diff --git a/api/test/services/UserServiceTest.kt b/api/test/integration/services/UserServiceTest.kt
similarity index 98%
rename from api/test/services/UserServiceTest.kt
rename to api/test/integration/services/UserServiceTest.kt
index d9a6c57..4cb9b4c 100644
--- a/api/test/services/UserServiceTest.kt
+++ b/api/test/integration/services/UserServiceTest.kt
@@ -1,4 +1,4 @@
-package services
+package integration.services
 
 import be.vandewalleh.mainModule
 import be.vandewalleh.migrations.Migration
diff --git a/api/test/unit/validation/RegisterValidationTest.kt b/api/test/unit/validation/RegisterValidationTest.kt
new file mode 100644
index 0000000..b2ea374
--- /dev/null
+++ b/api/test/unit/validation/RegisterValidationTest.kt
@@ -0,0 +1,57 @@
+package unit.validation
+
+import be.vandewalleh.entities.User
+import be.vandewalleh.validation.user.registerValidator
+import org.amshove.kluent.*
+import org.junit.jupiter.api.*
+import utils.firstInvalid
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class RegisterValidationTest {
+
+    @Test
+    fun `valid register test`() {
+        val violations = registerValidator.validate(User {
+            username = "hubert"
+            password = "definitelyNotMyPassword"
+            email = "test@mail.com"
+        })
+
+        violations.isValid `should be equal to` true
+    }
+
+    @Test
+    fun `invalid email test`() {
+        val violations = registerValidator.validate(User {
+            username = "hubert"
+            password = "definitelyNotMyPassword"
+            email = "teom"
+        })
+
+        violations.isValid `should be equal to` false
+        violations.firstInvalid `should be equal to` "email"
+    }
+
+    @Test
+    fun `missing email test`() {
+        val violations = registerValidator.validate(User {
+            username = "hubert"
+            password = "definitelyNotMyPassword"
+        })
+
+        violations.isValid `should be equal to` false
+        violations.firstInvalid `should be equal to` "email"
+    }
+
+    @Test
+    fun `username too long test`() {
+        val violations = registerValidator.validate(User {
+            username = "6X9iboWmEOWjVjkO328ReTJ1gGPTTmB/ZGgBLhB6EzAJoWkJht8"
+            password = "definitelyNotMyPassword"
+            email = "test@mail.com"
+        })
+
+        violations.isValid `should be equal to` false
+        violations.firstInvalid `should be equal to` "username"
+    }
+}
diff --git a/api/test/utils/ValidationExtensions.kt b/api/test/utils/ValidationExtensions.kt
new file mode 100644
index 0000000..91e461a
--- /dev/null
+++ b/api/test/utils/ValidationExtensions.kt
@@ -0,0 +1,6 @@
+package utils
+
+import am.ik.yavi.core.ConstraintViolations
+
+val ConstraintViolations.firstInvalid: Any?
+    get() = this.violations().firstOrNull()?.name()