diff --git a/backend/src/auth/auth.service.spec.ts b/backend/src/auth/auth.service.spec.ts
index 6564cb8..4a18178 100644
--- a/backend/src/auth/auth.service.spec.ts
+++ b/backend/src/auth/auth.service.spec.ts
@@ -148,7 +148,7 @@ describe("AuthService", () => {
 			const dto = {
 				username: "test",
 				email: "test@example.com",
-				password: "password",
+				password: "Password1!",
 			};
 			mockHashingService.hashPassword.mockResolvedValue("hashed-password");
 			mockHashingService.hashEmail.mockResolvedValue("hashed-email");
@@ -165,7 +165,7 @@ describe("AuthService", () => {
 
 	describe("login", () => {
 		it("should login a user", async () => {
-			const dto = { email: "test@example.com", password: "password" };
+			const dto = { email: "test@example.com", password: "Password1!" };
 			const user = {
 				uuid: "user-id",
 				username: "test",
diff --git a/backend/src/auth/dto/register.dto.ts b/backend/src/auth/dto/register.dto.ts
index 2dbc5ec..435435c 100644
--- a/backend/src/auth/dto/register.dto.ts
+++ b/backend/src/auth/dto/register.dto.ts
@@ -2,6 +2,7 @@ import {
 	IsEmail,
 	IsNotEmpty,
 	IsString,
+	Matches,
 	MaxLength,
 	MinLength,
 } from "class-validator";
@@ -10,6 +11,9 @@ export class RegisterDto {
 	@IsString()
 	@IsNotEmpty()
 	@MaxLength(32)
+	@Matches(/^[a-z0-9_]+$/, {
+		message: "username must contain only lowercase letters, numbers, and underscores",
+	})
 	username!: string;
 
 	@IsString()
@@ -21,5 +25,15 @@ export class RegisterDto {
 
 	@IsString()
 	@MinLength(8)
+	@Matches(/[A-Z]/, {
+		message: "password must contain at least one uppercase letter",
+	})
+	@Matches(/[a-z]/, {
+		message: "password must contain at least one lowercase letter",
+	})
+	@Matches(/[0-9]/, { message: "password must contain at least one number" })
+	@Matches(/[^A-Za-z0-9]/, {
+		message: "password must contain at least one special character",
+	})
 	password!: string;
 }
diff --git a/frontend/src/app/(auth)/login/page.tsx b/frontend/src/app/(auth)/login/page.tsx
index 42d5ca0..6316d94 100644
--- a/frontend/src/app/(auth)/login/page.tsx
+++ b/frontend/src/app/(auth)/login/page.tsx
@@ -30,7 +30,7 @@ const loginSchema = z.object({
 	email: z.string().email({ message: "Email invalide" }),
 	password: z
 		.string()
-		.min(6, { message: "Le mot de passe doit faire au moins 6 caractères" }),
+		.min(8, { message: "Le mot de passe doit faire au moins 8 caractères" }),
 });
 
 type LoginFormValues = z.infer<typeof loginSchema>;
diff --git a/frontend/src/app/(auth)/register/page.tsx b/frontend/src/app/(auth)/register/page.tsx
index 1a52bb1..a2756bf 100644
--- a/frontend/src/app/(auth)/register/page.tsx
+++ b/frontend/src/app/(auth)/register/page.tsx
@@ -29,11 +29,24 @@ import { useAuth } from "@/providers/auth-provider";
 const registerSchema = z.object({
 	username: z
 		.string()
-		.min(3, { message: "Le pseudo doit faire au moins 3 caractères" }),
+		.min(3, { message: "Le pseudo doit faire au moins 3 caractères" })
+		.regex(/^[a-z0-9_]+$/, {
+			message: "Le pseudo ne doit contenir que des minuscules, chiffres et underscores",
+		}),
 	email: z.string().email({ message: "Email invalide" }),
 	password: z
 		.string()
-		.min(6, { message: "Le mot de passe doit faire au moins 6 caractères" }),
+		.min(8, { message: "Le mot de passe doit faire au moins 8 caractères" })
+		.regex(/[A-Z]/, {
+			message: "Le mot de passe doit contenir au moins une majuscule",
+		})
+		.regex(/[a-z]/, {
+			message: "Le mot de passe doit contenir au moins une minuscule",
+		})
+		.regex(/[0-9]/, { message: "Le mot de passe doit contenir au moins un chiffre" })
+		.regex(/[^A-Za-z0-9]/, {
+			message: "Le mot de passe doit contenir au moins un caractère spécial",
+		}),
 	displayName: z.string().optional(),
 });
 
@@ -84,12 +97,25 @@ export default function RegisterPage() {
 					<CardContent>
 						<Form {...form}>
 							<form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
+								<FormField
+									control={form.control}
+									name="displayName"
+									render={({ field }) => (
+										<FormItem>
+											<FormLabel>Nom d'affichage (Optionnel)</FormLabel>
+											<FormControl>
+												<Input placeholder="Le Roi des Chèvres" {...field} />
+											</FormControl>
+											<FormMessage />
+										</FormItem>
+									)}
+								/>
 								<FormField
 									control={form.control}
 									name="username"
 									render={({ field }) => (
 										<FormItem>
-											<FormLabel>Pseudo</FormLabel>
+											<FormLabel>Pseudo (minuscule)</FormLabel>
 											<FormControl>
 												<Input placeholder="supergoat" {...field} />
 											</FormControl>
@@ -110,19 +136,6 @@ export default function RegisterPage() {
 										</FormItem>
 									)}
 								/>
-								<FormField
-									control={form.control}
-									name="displayName"
-									render={({ field }) => (
-										<FormItem>
-											<FormLabel>Nom d'affichage (Optionnel)</FormLabel>
-											<FormControl>
-												<Input placeholder="Le Roi des Chèvres" {...field} />
-											</FormControl>
-											<FormMessage />
-										</FormItem>
-									)}
-								/>
 								<FormField
 									control={form.control}
 									name="password"