If you are an owner of one web site, a blog or more, you will want to know the uptime of your webhosting–because poor uptimes means users won’t be confident about your product/website. The site constantly accessible to your users is very important.

So, how can we know the status of our sites? In this article, you will find free and useful monitoring tools to help you know when your website or web application becomes unavailable.

Siteuptime.com

SiteUpTime provides 3 plans: Free Plan which monitors one site for you at 30 and 60 minute interval, Premium Plan which is currently$5/month and will monitor 3 sites at 5 or 15 minute intervals, Advanced Plan which is currently $10/month which monitors 6 sites at 5 or 15 minute intervals all of the features of the premium plans plus some really cool stuf.

SiteUpTime notifies you via email or SMS if your site becomes unavailable, they currently have over 70,000 websites monitored. ( Ntt.cc is using SiteUpTime).

Host-Tracker.com

HostTracker is a free web tool for monitoring site availability. You can monitor up to two websites at a time and get free weekly, monthly, quarterly, and yearly reports on your web server’s performance.It is possibility to receive error notifications both to your Email, ICQ, GTalk or cell-phone via SMS;

Site24×7.com

Site24×7 will monitor any website from 15 locations; tracking the end-user experience from six sites in the US, three sites in Europe, and four in Asia, Australia and Africa. They provides REST style Web APIs(SaaS-Based) over HTTP. With this API, users/developers can extend their web applications to pull data from Site24×7.

Mon.itor.us

mon.itor.us is a free site monitoring tool with loads of useful features that will help you maintain a high uptime. They provide a fresh, novel approach to web and systems monitoring.has an intuitive dashboard GUI, the ability to send you downtime alerts via email, text message, and RSS, monitoring from multiple geographical locations, and real-time visitor monitoring.

mon.itor.us is a community based and community driven service with frequent release cycles and participatory features but it is free for users because they are financing the service via online advertisements.

Montastic.com

Montastic is a free, quick, and easy-to-use tool for keeping constant knowledge of your websites’ availability. You will get an email when your site goes down and an email when your site goes back. Support RSS, or their Windows and Mac widget. Max 100 sites can be added per account. HTTP and HTTP Secure connections(https) monitoring are supported.

Are My Sites Up?

I like this creative name “Are My Sites Up” and “When your websites go down, shouldn’t you be the first to know?”,

Are My Sites Up? likes their name, is a straightforward free web tool for being alerted when your websites are down. You can monitor up to five different websites, receive email and text message alerts with it. Their premium plans offer significantly more features: Faster site checks, an iPhone application, RSS feeds, Twitter integration, Keyword search, premium-level support.

ServerMojo.com

ServerMojo is a simple-to-use service for supervising your web server’s uptime. It alerts you via IM, Twitter, and email when your site is unavailable. ServerMojo is not free, you can try it for free but $9.95 is needed for single site. It seems they add something javascript to refresh/reload the homepage when you browse.

InternetSeer.com

InternetSeer provides a free standard service that offers 60-minute intervals for monitoring your site’s uptime and performance, the futures like “Variable Time zone Reporting”, “Custom Reports using Client Name and Logo”, “Customer Report Portal” and “Suspension Scheduler” are support in advanced plan, they also provide Pro and Enterpise plan.

Livewatch.de

Livewatch.de is ultimate solution to monitor your server and website, Livewatch.de allows you to get alerts when your site is unavailable via email, SMS, phone, IM, and even Twitter. But not only by these- they also give you a phonecall too.

Observu.com

Observu allows you to keep track of an unlimited number of sites, all for free. It is very very easy to use because the design is very very simple! Quickly register!When you create an account, you’ll be asked to input your email. This allows the service to contact you in case one of your sites crashes or needs to be updated. The service was created by Moving Labs. These folks have created other great apps. The service thrives on simplicity, so it doesn’t matter if you are running a network of a thousand sites or you want to know how your blog is doing, you’ll be able to figure it out

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FreeSiteStatus.com

FreeSiteStatus.com offers website downtime monitoring and notification alerts for free. Provides email alerts of your site’s downtime, a monitoring interval of 60 minutes, and a distributed monitoring network of 13 global locations.

BasicState.com

Basic State is a free monitoring tool for uptime, server, and network failures of your site. Basic State checks your website at 15-minute intervals. and sends you notifications via email or text message when something goes kaboom.

Server Density

Different with others Server Density is a service for VPS owner, In addition to notifying you when there’s downtime, it can also notify you when too much RAM is being used, or the load is too high, or the swap file is starting to be used.All accounts get access to metrics for load average, memory usage, process count and the process resource breakdown from the server snapshot.

Stopeo.com

With stopeo, You can easily check your server performance and keep an eye for any overloads.

monpage.com

Monpage is a server monitoring service. Monpage monitors the responsiveness of servers and web pages and display the information in easily comprehensible graphic form. They also provide access to the raw data via JSON (Java script object notation) feed.

What tool do you use to for monitoring uptime/availability? If you have a tool not on the list please do share it with us in the comments.