Quicklook is a great feature of OS X, allowing you to press the spacebar when a file is selected in Finder and quickly look at the contents. If you’re unfamiliar with Quicklook, check out this great introductory article.
As great as this is, there are a few occasions where it would be useful to quicklook a file that is not supported by default. Luckily, Quicklook is extendable with plugins; here are my favorite four.
BetterZip QuickLookGenerator lets you peer at the contents of an archive file (ZIP, TAR, GZip, BZip2, ARJ, LZH, ISO, CHM, CAB, CPIO, RAR, 7-Zip, DEB, RPM, SIT, DiskDoubler, BinHex, and MacBinary) without extracting it first.
Folder will display the contents of a folder. One might ask, why not just use Finder to view the contents of a folder, since that is really its job? I often will navigate to a top directory with Finder, and then bring up QuickLook. I then use the arrow keys to navigate that top directory, with Quicklook still open. This lets me peer at all files, including any subdirectories, without breaking my navigation method.
Suspicious Package lets you peer into the contents of a .pkg file, often used as application installers. This is also useful to browse the package receipts in your machine’s Receipt directory (in /Library/Receipts) which represents all packages previously installed. This is handy if you need to manually clean up packages.
Color Code gives you syntax highlighted source code. This supports a range of source files from the standards like C, Java, Pascal, XML and Plists (which are usually just XML, anyway). This is great for quickly glancing at any source code files you need to.
Other File Formats
To see if a Quicklook plugin exists for a specific file format you use, such as Adobe Illustrator (ai), Flash Video (flv) and more (even Commodore 64 disk images), check out qlplugins.com for an up-to-date list of available plugins.
Quicklook plugins are generally distributed without an installer. To install Quicklook plugins where an installer is not provided, copy the .qlgenerator file to either
/Library/QuickLook/ (to be available for all users) or
/Users/username/Library/QuickLook/ (to be available for just that username).
To uninstall these, simply delete the .qlgenerator file from where you installed it.