How to install an extension in Apple's Safari 5 browser?

That's a good question! By default, Apple seems to have left the extensions capability turned off, even though it is now added to the latest version of Safari. Worse, as far as I can tell, there's going to only be an Apple vetted official repository of Safari extensions, in a manner quite similar to how the company manages and controls all apps that show up on the iPhone or iPad.

Well, this isn't the place to complain about the politics of the situation, as much as I am a long-time supporter of free and open source software. I expect people will figure things out and we'll have a thriving third-party extension set if Safari 5 proves to garner a substantial percentage of the marketplace.

In the meantime, here's how you proceed...

Launch Safari 5.0, then go to "Preferences..." (or press Cmd-;) and then the "Advanced" tab:

See the checkbox at the bottom? You need to select "Show Develop menu in menu bar". Now along the top you'll see a new menu, Develop:

You guessed it, choose "Enable Extensions". Now when you go back to your "Preferences..." you'll see a new option:

There we go!

Now, the problem is that the Apple Safari 5 extensions library doesn't exist yet. The best resource I've been able to find so far is Safari Extensions Directory by Jonas Wisser.

Go there, poke around, and you'll see that there are some, albeit few, extensions so far.

To demonstrate how to install one, I'll pick Amazon Search Bar. Click on that link (conveniently duplicated here) and you'll see there are two options for getting the extension itself:

I opted for the Mac Package, clicked on it, downloaded, and launched the installer (unlike extension managers like Google Chrome or Firefox, Safari 5 doesn't have a built-in extension installer).

The first thing I get is this error from the installer:

Okay, I quit Safari 5 and re-launch the installer. It installs, and part way along the process, Safari starts up again and says:

I do want to have it installed in Safari so I click on "Install". I love that modern browsers warn you when code is about to be installed, by the way. Far better than the old days when code snippets and spyware would just worm their way into your system unannounced...

The Amazon extension is indeed installed and running, when I look:

Even more interesting, "Preferences..." --> "Extensions" now has content:

Anyway, you're on your own at this point. You can see how to work with Safari 5 extensions, but in terms of what will show up and whether Apple will evolve a more sophisticated and self-contained extension management system remains to be seen.