File Formats

For internet work there are two types of files you need to be familiar with: JPG and GIF. There are many other file types but the vast majority of all images on the internet are one of these two formats.

Choosing Which Format to Use

Unless you have a very good reason to use a different format, you should always use either JPG or GIF for your internet files. Indeed, many browsers and email programs will only recognise these formats.

JPG: This format is best for images with a large number of colours, such as photographs. JPG (or JPEG) actually stands for Joint Photographic Experts Group, and this format was specifically developed for use with photos.
Most photo-image software applications which come with cameras and scanners tend to use JPG by default.

GIF: Use this format for images with a lower number of colours and with strong, clearly defined lines. Images which contain simple shapes and/or text usually use gif, e.g. logos, buttons, icons, etc. You may also find that small thumbnail-sized photo images can work better as gif.

Rule of Thumb
Photos:  Use JPG	Logos:  Use GIF

If you're not sure which format to use, save your image in two versions - one of each. You can then compare image quality and file size to see which is best.

Viewing Image Properties

Before we go any further, here's a handy trick: You can view the basic properties of most images on the internet by right-clicking the image and selecting "Properties" (or the equivalent option in your browser). This will tell you the file type, file name, file size and pixel dimensions.

Next Step: Optimising an Image