In the Classic days, if you wanted to use a window that wasn't frontmost, you could click anywhere on it to bring it to the front. Mac OS X introduced a feature called "click-through" where certain controls, like the "traffic-light" buttons in the window title, would work even for background windows. Applications can also make other controls, or even the entire window, work with click-through. To make things a little confusing, in older versions, click-through was off by default for Carbon apps, but on by default for Cocoa apps.

Some people (including myself) never got used to click-through; if you too wish to have more control over what happens when you click on a background window, Klicko may solve your problem. Klicko also has two other convenient functions: window maximizing and bringing all windows of some application to the front.

Klicko is a System Preferences panel written in Cocoa. It doesn't hack the system, other applications, inject code or do anything magic. See below for details. Version 1.1.1 (Size: 255105 bytes) is for Mac OS X 10.5 (Leopard) and up, for both PowerPC and Intel.

Klicko is freeware. However, if you think it was useful to you, you may contribute with a donation.

Klicko is currently localized into English, Portuguese (Brazilian), German (with the help of M. Uli Kusterer) and French (by Ronald Leroux). Please contact me if you're interesting in doing some other language (Japanese and Spanish would be welcome).

Here's the Klicko preferences tab:

The popup menu in the window title is important. If it's set to "Excluded Applications", all windows belonging to the applications listed in the window won't be affected by Klicko; if it's set to "Included Applications", only those applications will be affected. That is, the popup changes the nature of the application list. Usually, you would set it to "Excluded" and list only the (hopefully few) applications you find incompatible.

You can add any running application by clicking on the "+" button; a pop-up menu will appear. You can also drag applications (running or not) from the Finder into (and out of) the window, of course. If you have several copies of an application installed, putting one of them in will work for all. In the example above, Klicko won't affect any of Safari's windows. Note that if you set the pop-up to "Included Applications", and put no application into the list, Klicko will have no effect at all.

Klicko has three functions which can be individually enabled, as you see in the preferences:

Beyond that, at any time you can direct any click to a window by holding down any modifier key. Some applications don't use standard windows or use them in a way that Klicko can't activate properly; if you find that clicking on a window has no effect at all, hold down a modifier key and try again, or try the exclusion list. Here are some known problem applications (which are added to the exclusion list automatically):

Klicko relies on the Accessibility interface, but you don't have to turn it on the System Preferences. Some applications may not implement Accessibility in a way that Klicko understands, and so one or all of the functions may not work properly for those. Please use the exclusion list in such a case.

Note that there's no way to disable the highlighting of the window "traffic light" buttons, so, to minimize user confusion Klicko always allows click-through on those buttons. Klicko will also always pass through clicks on windows belonging to background or full-screen applications, to dialogs, palettes, and similar interface elements, and to the Finder desktop.

Note that with click-through blocking, if you want to start a drag from a background window (say, a Finder window), you must hold down any modifier key first.

Code Signing: Klicko is codesigned for extra security. Basically, this means that you can verify if the application's executable has been signed by a specific developer, and that you can have some assurance that code or resources have not been tampered with by third parties.
To check that Klicko's signature is intact, open Terminal, paste in the following command, and press the Return key:

(assuming that you installed Klicko for all users; otherwise, type a tilde (~) before the /Library part.) You should see several result lines in the Terminal. Authority=Rainer Brockerhoff should be present, and identify the author. The last line should end with ...root = H"4cbb97c74336f7ee6aa566122a5e7688e1c725dc" and uniquely identify the author's signature. Now run the following command:

If the Klicko bundle is intact, this should display valid on disk; otherwise you'll see code or signature modified. In the latter case, throw it into the Trash.

The Klicko background application is also codesigned. To check it, just substitute its path in the commands above (note the quotes around the path, necessary because it contains a space):

Release Notes: Version 1.1 (181)

Release Notes: Version 1.1 (179)

Release Notes: Version 1.0.1 (123)

Release Notes: Version 1.0.1 (120)

Release Notes: Version 1.0.1 (119)

Release Notes: Version 1.0.1 (113)

Release Notes: Version 1.0.1 (109)

Release Notes: Version 1.0.1 (103)

Release Notes: Version 1.0.1 (97)

Release Notes: Version 1.0 (87)

Release Notes: Version 1.0 (79)

Release Notes: Version 1.0 (73)

Release Notes: Version 1.0 (71)

Release Notes: Version 1.0 (67)