EasyCron - Get frustrated with Cron on your server? Hosting limits your Cron use?
Cronitor - Monitor cron jobs, micro-services, daemons and almost anything else, no setup required. Easier cron troubleshooting and no more silent failures.
Cronly - Keep track of your cron jobs and SSL certificates. Don't let them fail unnoticed.
crontab guru - The quick and simple editor for cron schedule expressions by Cronitor
WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Crontab Generator - Crontab Generator is one of the advanced cron generating tools that are used by top-class professionals from all over the world, making them easily describe and generate complex cron expressions in no time.