A bookmarklet is very similar to a browser add-on or extension.
However, it requires no installion, and no restart.
It will not slow down your computer, and it is generally safer to use.
Bookmarklets are tiny programs stored inside bookmarks.
Similar to add-ons and extensions, they add new tools to your web browser.
Bookmarklets are shared on web pages as web links.
To add a bookmarklet to your browser, right click on it's web link and choose the bookmark option.
To use it, simply click on the new bookmark you added.
Pictures of bookmarklets in Internet Explorer and in FireFox
No Installing Necessary
You don't actually "install" a bookmarklet. You simply add it to your bookmarks. It just sits there patiently until you want to use it.
Add a bookmarklet to your links toolbar
for faster access.
When added to your links toolbar, bookmarklets are sometimes called "browser buttons".
Saftey Information about Bookmarklets
Because they can do more than standard web links, some browsers will give a warning when you add a bookmarklet
However, a bookmarklet is usually much safer to install than standard programs.
Some of the largest companies on the internet distribute bookmarklets,
including a bookmarklet from Google
a bookmarklet from Facebook
a bookmarklet from Delicious
which is owned by Yahoo!,
and a bookmarklet from Microsoft Live
Unlike a standard program, a bookmarklet can run only when you click it.
A bookmarklet can not access files on your hard drive.
A bookmarklet can affect only the web site you are viewing at the time you click it.
This is the same type of programming used in almost all of the top websites on the Internet.
All of these statements are generalizations only.
Like all software, you should not use bookmarklets from dangerous sources.
Also, you should never use a bookmarklet when you are visiting a site where security is critical, such as your bank's website.