The problem with the web is there's just so much of it; an endless tide of funny videos, pop quizzes, and social alerts ready to distract you from other, more urgent tasks at hand. We wouldn't say there's anything inherently wrong with killing time online, but if you really need to buckle down on an important job then these tools should help.
KeepMeOut works in any browser, creating customized bookmarks that you use in place of standard links. For example: instead of opening Facebook as you normally would, follow the KeepMeOut bookmark for Facebook. You can set limits on how often you can visit each website in a certain amount of time, and configure KeepMeOut to only operate during specific periods of the day.
StayFocusd is a free Chrome extension that lets you specify which websites you can visit and which are off limits. If you need access to the IMDB for your article on 1990s movie stars but want to block Facebook and Twitter, for example, then StayFocusd is ideal. It's incredibly customizable: you can set limits based on total time, specific times of day or specific days (such as Monday to Friday).
LeechBlock is perfect for Firefox users who want to take control over the sites and apps they're visiting online. In a couple of clicks you can block the site that you're currently visiting, or you can delve further into the options to organize sites into groups—in each case the software lets you specify certain times when the websites are out of bounds. There's also a full lockdown mode for emergency distraction-free working and a statistics page where you can see just how focused (or otherwise) you've been.
Cold Turkey (Windows only) does exactly what its name suggests, blocking apps and websites on a schedule set by you in advance. If you know you'll start scrolling through Tumblr near the end of the working day, use Cold Turkey to make sure that doesn't happen. It's clever too: you can't stop it through the task manager or by changing the system time, forcing you to get back to work if you start to waver. You can choose to donate for Cold Turkey, but it's optional.
SelfControl (Mac only) is a free application that can work in tandem with your own willpower to temporarily block access to websites and mail servers. Specify the sites you want to be kept away from, set the timer slider as necessary, and click Start; that's all there is to it. Even if you remove the app or restart your computer, the block will remain in place until the set amount of time has elapsed.
TomatoTimer is a Web-based app that uses the Pomodoro technique to help you get things done. If you're new to the Pomodoro idea, it involves working in short bursts that are broken up with regular breaks. TomatoTimer won't block any distractions for you, but it does help you keep on top of the timings very easily from any browser. Treat yourself to a five-minute burst of Angry Birds for every 25 minutes of work, or whatever combination suits you.
Freedom (for Windows, Mac and Android) will cost you $10, but there's a 60-day money-back guarantee, and it has some high-profile fans (including authors Naomi Klein and Seth Rodin). It simply cuts off your Internet connection for a specified length of time: if you want to go completely cold turkey, and you don't need the Web for your work, then this is the one to go for. Think of it as the nuclear option. If you break and can't take it any more, you'll need to reboot your computer or device to get back online.