diff --git a/src/app.d.ts b/src/app.d.ts
index da08e6d..78c38dc 100644
--- a/src/app.d.ts
+++ b/src/app.d.ts
@@ -2,7 +2,10 @@
 // for information about these interfaces
 declare global {
 	namespace App {
-		// interface Error {}
+		interface Error {
+			message: string
+			cause?: number,
+		}
 		// interface Locals {}
 		// interface PageData {}
 		// interface PageState {}
diff --git a/src/lib/errors.ts b/src/lib/errors.ts
index 7a31215..a80b6e2 100644
--- a/src/lib/errors.ts
+++ b/src/lib/errors.ts
@@ -4,3 +4,22 @@ export class ArgumentError extends Error {
 		super(message)
 	}
 }
+
+export class DuplicateError extends Error {
+	fields: Array<string>
+
+	constructor(fields: Array<string>, message: string) {
+		super(message)
+		this.fields = fields
+	}
+}
+
+export const enum RegisterResponseCause {
+	Server = 1,
+	MalformedRequest,
+	EmailLength,
+	EmailFormat,
+	EmailDuplicate,
+	PasswordLength,
+	DisplayNameLength
+}
diff --git a/src/lib/server/log.ts b/src/lib/server/log.ts
index d116111..3eb90ce 100644
--- a/src/lib/server/log.ts
+++ b/src/lib/server/log.ts
@@ -10,7 +10,8 @@ export enum LogSeverity {
 
 export enum LogModule {
 	PROCESS,
-	USER
+	USER,
+	DATABASE
 }
 
 abstract class Logger {
diff --git a/src/lib/server/usermgmt.ts b/src/lib/server/usermgmt.ts
index 7299801..b885797 100644
--- a/src/lib/server/usermgmt.ts
+++ b/src/lib/server/usermgmt.ts
@@ -1,9 +1,10 @@
 import Bun from "bun"
 
-import { ArgumentError } from "$lib/errors"
+import { ArgumentError, DuplicateError } from "$lib/errors"
 
 import Log from "$lib/server/log"
 import db from "$lib/server/database"
+import { Prisma } from "@prisma/client"
 
 class UserMgmt {
 
@@ -11,19 +12,29 @@ class UserMgmt {
 		if (email.length == 0 || password.length == 0 || display_name.length == 0) {
 			throw new ArgumentError("No field may be empty")
 		}
+		
+		try {
+			const user = await db.user.create({
+				data: {
+					email: email,
+					password_hash: await Bun.password.hash(password, "argon2id"),
+					display_name: display_name
+				}
+			})
 
-		const user = await db.user.create({
-			data: {
-				email: email,
-				password_hash: await Bun.password.hash(password, "argon2id"),
-				display_name: display_name
+			Log.info(Log.module.USER, `Created user with id ${user.id}`)
+			console.log(user)
+
+			return user;
+		} catch (e) {
+			if (e instanceof Prisma.PrismaClientKnownRequestError && e.code == "P2002") {
+				const duplicates = Array.isArray(e.meta?.target) ? e.meta.target as Array<string> : ["unknown"]
+				throw new DuplicateError(duplicates, "Already exists")
 			}
-		})
 
-		Log.info(Log.module.USER, `Created user with id ${user.id}`)
-		console.log(user)
-
-		return user;
+			Log.error(Log.module.DATABASE, `Failed to create User in database! Error: ${JSON.stringify(e)}`)
+			return null
+		}
 	}
 
 	async login(email: string, password: string) {
diff --git a/src/routes/api/register/+server.ts b/src/routes/api/register/+server.ts
index b1949e1..9380627 100644
--- a/src/routes/api/register/+server.ts
+++ b/src/routes/api/register/+server.ts
@@ -5,6 +5,7 @@ import { json, error } from "@sveltejs/kit"
 import UserMgmt from "$lib/server/usermgmt"
 
 import Util from "$lib/util"
+import { DuplicateError, RegisterResponseCause } from "$lib/errors"
 
 export const POST: RequestHandler = async ({ request }) => {
 	
@@ -15,26 +16,32 @@ export const POST: RequestHandler = async ({ request }) => {
 	const display_name = data.get("display_name")
 
 	if (data.keys.length > 3 || !(typeof email === "string" && typeof password === "string" && typeof display_name === "string")) {
-		return error(400, { message: "Invalid field arguments" })
+		return error(400, { cause: RegisterResponseCause.MalformedRequest, message: "Invalid field arguments" })
 	}
 	if (email.length == 0) {
-		return error(400, { message: "email must not be empty" })
+		return error(400, { cause: RegisterResponseCause.EmailLength, message: "email must not be empty" })
 	}
 	if (password.length == 0) {
-		return error(400, { message: "password must not be empty" })
+		return error(400, { cause: RegisterResponseCause.PasswordLength, message: "password must not be empty" })
 	}
 	if (display_name.length == 0) {
-		return error(400, { message: "Display name must not be empty" })
+		return error(400, { cause: RegisterResponseCause.DisplayNameLength, message: "Display name must not be empty" })
 	}
 
 	if (!Util.check_email_format(email)) {
-		return error(400, { message: "invalid email format" })
+		return error(400, { cause: RegisterResponseCause.EmailFormat, message: "invalid email format" })
 	}
 	
 	try {
-		const user = UserMgmt.register(email, password, display_name)
+		const user = await UserMgmt.register(email, password, display_name)
 	} catch (e) {
-		return error(500)
+		if (e instanceof DuplicateError) {
+			if (e.fields.includes("email")) {
+				return error(409, { cause: RegisterResponseCause.EmailDuplicate, message: "email already in use" })
+			}
+		}
+
+		return error(500, { cause: RegisterResponseCause.Server, message: "Server failed to create user"})
 	}
 	
 	return json({})