iMacros vs. Greasemonkey
What is iMacros?
First it is iMacros, the most popular extension for the web browsers includes Mozilla Firefox, Google Chrome and Internet Explorer that adds record and repeat works similar to that found in web testing and form filler software. iMacros was developed by iOpus in February 26, 2013 and is available in 11 international languages for Windows XP and later. In fact, it is a social scripting utility that allows the users to share macros and scripts in a way that is similar to how they share the bookmarks on the many social bookmarking websites. Both, free and proprietary version of iMacros are available.
What is Greasemonkey?
Greasemonkey is also an extension that is available for Mozilla Firefox only. It allows the users to store scripts that make on-the-fly changes to webpage content after or before the page is loaded in the web browser. This utility is useful for customizing page appearance, adding new features to web pages, fixing bugs, collecting data from multiple web pages, and many more. Hundreds of scripts are already available for free and if you are the tinkerer sort, you can also write your own.