diff --git a/src/lib/clientTools.js b/src/lib/clientTools.js
index 9dae7f3..345feac 100644
--- a/src/lib/clientTools.js
+++ b/src/lib/clientTools.js
@@ -149,7 +149,121 @@ function IsValidNameServer(nameServer) {
 const IsValidURL = function (url) {
 	return /^(http|https):\/\/[^ "]+$/.test(url);
 };
+function ValidateCronExpression(cronExp) {
+	// Check if expression is provided and is a string
+	if (!cronExp || typeof cronExp !== "string") {
+		return { isValid: false, message: "Cron expression must be a non-empty string" };
+	}
 
+	// Split the expression into its components
+	const fields = cronExp.trim().split(/\s+/);
+
+	// Standard cron should have 5 or 6 fields
+	// minute hour day-of-month month day-of-week [year]
+	if (fields.length < 5 || fields.length > 6) {
+		return {
+			isValid: false,
+			message: "Cron expression must have 5 or 6 fields"
+		};
+	}
+
+	// Define field constraints
+	const fieldConstraints = [
+		{ name: "minute", min: 0, max: 59 },
+		{ name: "hour", min: 0, max: 23 },
+		{ name: "day", min: 1, max: 31 },
+		{ name: "month", min: 1, max: 12 },
+		{ name: "weekday", min: 0, max: 6 },
+		{ name: "year", min: 1970, max: 2099 } // Optional field
+	];
+
+	// Valid characters in cron expressions
+	const validChars = /^[\d/*,\-]+$/;
+
+	// Validate each field
+	for (let i = 0; i < fields.length; i++) {
+		const field = fields[i];
+		const constraint = fieldConstraints[i];
+
+		// Check for valid characters
+		if (!validChars.test(field)) {
+			return {
+				isValid: false,
+				message: `Invalid characters in ${constraint.name} field`
+			};
+		}
+
+		// Handle special characters
+		if (field === "*") {
+			continue; // Asterisk is valid for all fields
+		}
+
+		// Handle lists (comma-separated values)
+		if (field.includes(",")) {
+			const values = field.split(",");
+			for (const value of values) {
+				if (!isValidRange(value, constraint.min, constraint.max)) {
+					return {
+						isValid: false,
+						message: `Invalid value in ${constraint.name} field: ${value}`
+					};
+				}
+			}
+			continue;
+		}
+
+		// Handle ranges (with hyphens)
+		if (field.includes("-")) {
+			const [start, end] = field.split("-").map(Number);
+			if (
+				start == null ||
+				end == null ||
+				start < constraint.min ||
+				end > constraint.max ||
+				start > end
+			) {
+				return {
+					isValid: false,
+					message: `Invalid range in ${constraint.name} field: ${field}`
+				};
+			}
+			continue;
+		}
+
+		// Handle steps (with forward slash)
+		if (field.includes("/")) {
+			const [range, step] = field.split("/");
+			if (range !== "*" && !isValidRange(range, constraint.min, constraint.max)) {
+				return {
+					isValid: false,
+					message: `Invalid range in ${constraint.name} field: ${range}`
+				};
+			}
+			if (!isValidRange(step, 1, constraint.max)) {
+				return {
+					isValid: false,
+					message: `Invalid step value in ${constraint.name} field: ${step}`
+				};
+			}
+			continue;
+		}
+
+		// Handle plain numbers
+		if (!isValidRange(field, constraint.min, constraint.max)) {
+			return {
+				isValid: false,
+				message: `Invalid value in ${constraint.name} field: ${field}`
+			};
+		}
+	}
+
+	return { isValid: true, message: "Valid cron expression" };
+}
+
+function isValidRange(value, min, max) {
+	const num = Number(value);
+	return !isNaN(num) && num >= min && num <= max;
+}
 export {
 	siteDataExtractFromDb,
 	storeSiteData,
@@ -157,5 +271,6 @@ export {
 	ValidateIpAddress,
 	IsValidHost,
 	IsValidNameServer,
-	IsValidURL
+	IsValidURL,
+	ValidateCronExpression
 };
diff --git a/src/lib/components/manage/monitorSheet.svelte b/src/lib/components/manage/monitorSheet.svelte
index d9786df..76c725b 100644
--- a/src/lib/components/manage/monitorSheet.svelte
+++ b/src/lib/components/manage/monitorSheet.svelte
@@ -11,6 +11,7 @@
 	import {
 		allRecordTypes,
 		ValidateIpAddress,
+		ValidateCronExpression,
 		IsValidHost,
 		IsValidNameServer
 	} from "$lib/clientTools.js";
@@ -130,13 +131,11 @@
 
 		//validating cron
 		const cron = newMonitor.cron;
-		const cronRegex =
-			/^((\*|([0-5]?\d)(-[0-5]?\d)?(\/[1-9]\d*)?|([0-5]?\d(,[0-5]?\d)*))\s+){4}(\*|([0-7](,[0-7])*|([0-7]-[0-7])))$/;
-		if (!cronRegex.test(cron)) {
-			invalidFormMessage = "Invalid Cron";
+		let cronValidation = ValidateCronExpression(cron);
+		if (cronValidation.isValid === false) {
+			invalidFormMessage = "Cron invalid: " + cronValidation.message;
 			return;
 		}
-
 		//if monitor type is API
 		if (newMonitor.monitor_type === "API") {
 			//validating url