Characters is described as 'makes it easy for writers, designers and developers to access special characters. They are easily found and copied to your clipboard, either as the character itself or the html code' and is an app in the Development category. There are more than 10 alternatives to Characters for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Android. The best alternative is BabelMap, which is free. Other great apps like Characters are Character Map (Free), WinCompose (Free, Open Source), Rocket (Freemium) and SymbSearch (Free, Open Source).
BabelMap is a free character map application for Windows that allows you to browse through the entire Unicode character repertoire of over 107,000 characters, or search for a particular character by name or by code point.
The character map that works! PopChar is an application that lets you insert special characters, umlauts and foreign letters into any document. With this character map, there is no need to search for or remember complex keystrokes.