Holdkey

Holdkey is a tiny and very practical application that lets you seamlessly insert special characters based on the Latin alphabet (like é à ø ü € ß ñ ï ç ö ę ğ) when you're typing a text document, regardless of the application you're working in.

Runs in the systray

After a fast setup operation that shouldn't give you any trouble, Holdkey starts running in the systray silently without interrupting your regular PC activities. It can be suspended and re-enabled by opening its right-click menu.

Easily insert special characters

Left-clicking the tray icon brings up to the screen the app's configuration panel, where you can find out how to insert special characters. All you have to do is hold down any alphabetical characters until an arrow sign appears, then release the key.
This triggers Holdkey to show a small horizontal frame right above the cursor, which includes 10 predefined special characters that you can add to your text document, provided that it supports UTF encoding. You can either click on a symbol using the mouse, or press its corresponding numerical key.

Find more characters at the developer's website

An extended list with all characters and symbols that you can use can be explored at the developer's website. In this list you can click on a character to automatically copy it to the Clipboard, and then paste it in the desired location.
Global keyboard shortcuts are available for opening the Holdkey interface, enabling and disabling it, as well as exiting it. As far as configuration settings are concerned, you can increase or decrease the speed from holding down a key to displaying the arrow sign, the repeat delay, and the delay for the arrow sign's display time.
Furthermore, you can change the bar color and size of the Holdkey info bar or hide it, use Caps Lock as the Shift key, enable multiple monitor support, and disable keyboard shortcuts.

Evaluation and conclusion

The program worked smoothly in our tests, without triggering the OS to hang, crash or prompt error messages. It had minimal impact on computer performance.
On the other hand, it doesn't let you modify the symbols displayed in the info bar for quick insertions, which means that you have to visit the developer's webpage, browse for the character, click it, and then paste it into your document. All these steps take a lot from Holdkey's ease of access. Moreover, this requires an active Internet connection. Nevertheless, you can test the app for yourself.