How to open Visio (and other unusual) file types

By: Mark Ellis

Date: 12 January 2017

There's nothing more frustrating than receiving an email attachment you can't open. You know the information contained within is absolutely vital, but no matter what you try, your computer will only do the digital equivalent of shrugging its shoulders before giving up.

A file type is an attribution applied to a file to make it recognisable to specific applications. It'll be three or four letters in length and appear after the filename; a file called 'offer.docx', for example, will tell the computer to open Microsoft Word.

As the tech industry has grown and multiple platforms have spawned, the number of file types in circulation has increased dramatically. Unfortunately, this often presents small businesses and casual users with something of a problem.

For a computer to use any kind of file, it needs to match the file's type with a compatible application. If it can't find the 

latter, it gives up and asks for user assistance. But what if you don't have the app to hand? It does, after all, seem rather unnecessary to invest in a piece of software that may only be used once.

Take Visio files. Visio is a piece of software written by Microsoft that enables users to draw complex diagrams. It's not a common installation, though, which is why a handy Visio viewer exists. It's free, easy to install and enables anyone to view Visio files without purchasing Visio itself.

That got us thinking - what other unusual file types exist and how do you go about opening them?

1. Installation files: ISO and DMG

If you download an app from a vendor website, there's a chance you'll be left with a file that doesn't appear to do anything. This may because you've downloaded a disk image rather than an installation file.

A disk image is what sits on a DVD or CD in order to initiate a software installation. Nowadays, you're far more likely to forgo tangible media and install directly from your hard drive, which makes the use of such files rather different from times of old.

DMG is a file format used by macOS, and should open easily with a double-click, enabling you to access the contents. As for ISOs, MagicISO or the built-in disk imaging utility on your computer should do the job.

2. Compressed files: ZIP (or 'RAR', '7ZIP', 'TAR' and 'SIT')

There are a huge number of ways to reduce the size of files to enable speedy transportation, but unpacking them at the other end can be a bit of a pain.

The quickest solution is to Google the compressed file type you've received. Tools such as WinZip, StuffIt Expander and WinRAR will do a fine job, but if you're lucky your operating system may do the hard work for you automatically (macOS is particularly adept at this).

3. Image files: PSD

Not everyone thinks to convert image files into common formats before sharing, and if someone has created a new brochure for you in Photoshop only to send you the Photoshop file itself, you'll have trouble accessing it unless you have that particular application installed.

Thankfully, Gimp exists for both Windows and macOS, and will open any Photoshop file that comes your way.

4. Video files: MP4, FLV or MKV

If you've requested video footage only to be disappointed when something drops into your inbox that is completely inaccessible, there are several options.

It's sometimes easier to convert such files by using applications like Handbrake, but another trick is to install Apple's iTunes and see if that will open or convert the file for you.

The universal file viewer

Of course, if all else fails, you could try one of the many universal file viewers on the market. They're not infallible, and will often only display the code contained within (that might be what you need), but are certainly worth a punt if you're stuck.