diff --git a/Makefile b/Makefile
index 0d0b06c..b622464 100644
--- a/Makefile
+++ b/Makefile
@@ -18,6 +18,8 @@ COMPLEX_DIR = radix
 
 FLAGS_DIR = flags
 
+CHECKER_DIR = checker
+
 INCLUDES = headers
 
 #============================
@@ -33,6 +35,8 @@ FLAGS_FILES = algorithms_sort.c flag.c bench.c
 PARSING = ft_atoi.c parsing.c ft_strncmp.c ft_split.c ft_strlen.c ft_substr.c checker.c ft_itoa.c ft_isdigit.c \
 			ft_strjoin.c ft_strlcat.c ft_strlcpy.c parsing_2.c
 
+CHECKER_FILES = check_error.c verif_flag.c verif_is_digit.c verif_overflow.c verif_double.c
+
 STACK_UTILS = push.c rev_rotate.c rotate.c stack_add.c stack_remove.c stacks_len.c swap.c print_stacks.c
 
 MEDIUM_ALGO = utils_medium.c utils_struct_tab.c utils_medium_two.c sort_utils.c sort_utils_two.c medium_algo.c
@@ -48,7 +52,7 @@ ALGO_UTILS = check_order.c compare.c iterate.c pre_sort.c
 ALL_FILES = $(SRC) $(STACK_UTILS_DIR)/$(STACK_UTILS)  $(PARS_DIR)/$(PARSING) \
 			$(ALGO_DIR)/$(MEDIUM_DIR)/$(MEDIUM_ALGO) $(ALGO_UTILS_DIR)/$(ALGO_UTILS) \
 			$(INSERT_DIR)/$(INSERTION) $(ALGO_DIR)/$(COMPLEX_DIR)/$(COMPLEX_ALGO) \
-			$(FLAGS_DIR)/$(FLAGS_FILES)
+			$(FLAGS_DIR)/$(FLAGS_FILES) $(CHECKER_DIR)/$(CHECKER_FILES)
 
 OBJ_DIR = obj
 
@@ -95,6 +99,9 @@ $(OBJ_DIR)/%.o: $(ALGO_UTILS_DIR)/%.c | $(OBJ_DIR)
 $(OBJ_DIR)/%.o: $(FLAGS_DIR)/%.c | $(OBJ_DIR)
 	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
 
+$(OBJ_DIR)/%.o: $(CHECKER_DIR)/%.c | $(OBJ_DIR)
+	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
+
 $(OBJ_DIR)/%.o: %.c | $(OBJ_DIR)
 	$(CC) $(CFLAGS) -MMD -MP -c $< -o $@
 
diff --git a/checker/check_error.c b/checker/check_error.c
new file mode 100644
index 0000000..b549333
--- /dev/null
+++ b/checker/check_error.c
@@ -0,0 +1,28 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   check_error.c                                      :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 09:31:50 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 09:31:51 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "check_error.h"
+
+int	check_error(char **tab, int mod)
+{
+	if (!verif_flag(tab, mod))
+		return (0);
+	if (!verif_is_digit(tab, mod))
+		return (0);
+	if (!verif_overflow(tab, mod))
+		return (0);
+	if (!verif_double(tab, mod))
+		return (0);
+	return (1);
+}
+
+
diff --git a/checker/verif_double.c b/checker/verif_double.c
new file mode 100644
index 0000000..bdc7ccc
--- /dev/null
+++ b/checker/verif_double.c
@@ -0,0 +1,47 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   verif_double.c                                     :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 10:41:42 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 10:41:43 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "parsing.h"
+#include "check_error.h"
+
+static int	is_double_in_tab(char **tab, int nb, int pos)
+{
+	int	i;
+
+	i = pos;
+	while (tab[i])
+	{
+		if (nb == ft_atoi(tab[i]))
+			return (0);
+		i++;
+	}
+	return (1);
+}
+
+int	verif_double(char **tab, int mod)
+{
+	int	i;
+	int	tmp;
+
+	i = wich_mod(mod);
+	while (tab[i])
+	{
+		if (tab[i + 1])
+		{
+			tmp = ft_atoi(tab[i]);
+			if (!is_double_in_tab(tab, tmp, i + 1))
+				return (0);
+		}
+		i++;
+	}
+	return (1);
+}
diff --git a/checker/verif_flag.c b/checker/verif_flag.c
new file mode 100644
index 0000000..8ad3d76
--- /dev/null
+++ b/checker/verif_flag.c
@@ -0,0 +1,60 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   verif_flag.c                                       :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 09:51:11 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 09:51:12 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "parsing.h"
+
+static int	is_exist_flag(char **tab, int pos)
+{
+	int	verif;
+
+	verif = 0;
+	if (ft_strncmp(tab[pos], "--bench", 7)
+		|| ft_strncmp(tab[pos], "--simple", 8)
+		|| ft_strncmp(tab[pos], "--medium", 8)
+		|| ft_strncmp(tab[pos], "--complex", 9))
+		verif = 1;
+	return (verif);
+}
+
+static int	verif_exist_flag(char **tab, int mod)
+{
+	int	verif;
+
+	verif = 0;
+	if (mod == 1)
+		verif = (is_exist_flag(tab, 1));
+	else if (mod == 2)
+	{
+		if (is_exist_flag(tab, 1) && is_exist_flag(tab, 2))
+			verif = 1;
+	}
+	return (verif);
+}
+
+static int verif_double_flag(char **tab, int mod)
+{
+	int	verif;
+
+	verif = 1;
+	if (mod == 2 && ft_strncmp(tab[1], tab[2], 9))
+		verif = 0;
+	return (verif);
+}
+
+int	verif_flag(char **tab, int mod)
+{
+	if (mod == 0)
+		return (1);
+	if (verif_double_flag(tab, mod) && verif_exist_flag(tab, mod))
+		return (1);
+	return (0);
+}
\ No newline at end of file
diff --git a/checker/verif_is_digit.c b/checker/verif_is_digit.c
new file mode 100644
index 0000000..65b4e0a
--- /dev/null
+++ b/checker/verif_is_digit.c
@@ -0,0 +1,41 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   verif_is_digit.c                                   :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 10:25:23 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 10:25:24 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "parsing.h"
+
+static int	scan_str_is_digit(char *tab)
+{
+	int	i;
+
+	i = 0;
+	while (tab[i])
+	{
+		if (!ft_isdigit(tab[i]) && (tab[i] == '-' && !ft_isdigit(tab[i + 1])))
+			return (0);
+		i++;
+	}
+	return (1);
+}
+
+int	verif_is_digit(char **tab, int mod)
+{
+	int	i;
+
+	i = wich_mod(mod);
+	while (tab[i])
+	{
+		if (!scan_str_is_digit(tab[i]))
+			return (0);
+		i++;
+	}
+	return (1);
+}
diff --git a/checker/verif_overflow.c b/checker/verif_overflow.c
new file mode 100644
index 0000000..d9aa159
--- /dev/null
+++ b/checker/verif_overflow.c
@@ -0,0 +1,51 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   verif_overflow.c                                   :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 10:30:39 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 10:30:40 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#include "parsing.h"
+
+static int	verif_atoi(const char *nptr)
+{
+	size_t	i;
+	int		tmp;
+	int		before;
+
+	i = 0;
+	tmp = 0;
+	before = 0;
+	while ((nptr[i] >= 9 && nptr[i] <= 13) || nptr[i] == ' ')
+		i++;
+	if (nptr[i] == '-' || nptr[i] == '+')
+		i++;
+	while (nptr[i] >= '0' && nptr[i] <= '9')
+	{
+		before = tmp;
+		tmp = tmp * 10 + nptr[i] - '0';
+		if (before > tmp)
+			return (0);
+		i++;
+	}
+	return (1);
+}
+
+int	verif_overflow(char **tab, int mod)
+{
+	int	i;
+
+	i = wich_mod(mod);
+	while (tab[i])
+	{
+		if (!verif_atoi(tab[i]))
+			return (0);
+		i++;
+	}
+	return (1);
+}
diff --git a/headers/check_error.h b/headers/check_error.h
new file mode 100644
index 0000000..a9a506a
--- /dev/null
+++ b/headers/check_error.h
@@ -0,0 +1,22 @@
+/* ************************************************************************** */
+/*                                                                            */
+/*                                                        :::      ::::::::   */
+/*   check_error.h                                      :+:      :+:    :+:   */
+/*                                                    +:+ +:+         +:+     */
+/*   By: mteriier <mteriier@student.42lyon.fr>      +#+  +:+       +#+        */
+/*                                                +#+#+#+#+#+   +#+           */
+/*   Created: 2026/01/09 10:16:35 by mteriier          #+#    #+#             */
+/*   Updated: 2026/01/09 10:16:37 by mteriier         ###   ########lyon.fr   */
+/*                                                                            */
+/* ************************************************************************** */
+
+#ifndef CHECK_ERROR_H
+# define CHECK_ERROR_H
+
+int	verif_flag(char **tab, int mod);
+int	check_error(char **tab, int mod);
+int	verif_is_digit(char **tab, int mod);
+int	verif_overflow(char **tab, int mod);
+int	verif_double(char **tab, int mod);
+
+#endif
diff --git a/headers/parsing.h b/headers/parsing.h
index 72b0410..8925ce6 100644
--- a/headers/parsing.h
+++ b/headers/parsing.h
@@ -17,6 +17,7 @@
 # include "push_swap.h"
 
 int			ft_atoi(const char *nptr);
+int			wich_mod(int mod);
 t_stacks	*init_stacks(int argc, char **argv, int mod);
 int			ft_strncmp(const char *s1, const char *s2, int n);
 size_t		ft_strlen(const char *s);
diff --git a/headers/push_swap.h b/headers/push_swap.h
index 495fef0..c039fe4 100644
--- a/headers/push_swap.h
+++ b/headers/push_swap.h
@@ -79,7 +79,7 @@ int		check_order(t_stack *stack);
 void	insertion(t_stacks *stacks, int len);
 int		test2(char **argv);
 /* TEST FILE */
-int		test1(int argc, char **argv);
+int		test1(char **tab, int len, int mod);
 
 /* RADIX */
 void	radix(t_stacks *stacks);
diff --git a/main.c b/main.c
index 13a55be..4c8434e 100644
--- a/main.c
+++ b/main.c
@@ -12,16 +12,25 @@
 
 #include "push_swap.h"
 #include "parsing.h"
+#include "check_error.h"
+#include "flags.h"
 #include <unistd.h>
 
 int	main(int argc, char **argv)
 {
-	// if (!checker(argc, argv))
-	// {
-	// 	write(2, "Error !\n", 8);
-	// 	return (1);
-	// }
-	if (argc > 1)
-		test1(argc, argv);
+	char	**tab;
+	int		mod;
+	int		len;
+
+	tab = split_all(join_all(argc, argv));
+	if (!tab)
+		return (0);
+	len = len_split(tab);
+	mod = calcul_mod(len, tab);
+	if (check_error(tab, mod))
+		test1(tab, len, mod);
+	else
+		write(2, "Error\n", 7);
+	free_tab(tab);
 	return (0);
 }
diff --git a/parsing/parsing.c b/parsing/parsing.c
index 787aa3b..3a80a9c 100644
--- a/parsing/parsing.c
+++ b/parsing/parsing.c
@@ -14,7 +14,7 @@
 #include "parsing.h"
 #include <stdlib.h>
 
-static int	wich_mod(int mod)
+int	wich_mod(int mod)
 {
 	if (mod == 0)
 		return (1);
diff --git a/test_one.c b/test_one.c
index 8faa47a..88a33bb 100644
--- a/test_one.c
+++ b/test_one.c
@@ -16,19 +16,11 @@
 #include "medium_headers.h"
 #include <stdlib.h>
 
-int	test1(int argc, char **argv)
+int	test1(char **tab, int len, int mod)
 {
 	t_stacks	*stacks;
-	int			mod;
-	char		**tab;
-	int			len;
 
 	stacks = NULL;
-	tab = split_all(join_all(argc, argv));
-	if (!tab)
-		return (0);
-	len = len_split(tab);
-	mod = calcul_mod(len, tab);
 	if (mod == -1)
 		return (0);
 	stacks = init_stacks(len, tab, mod);