Filtering and sorting are essential for helping users find the products they're looking for. How can you make best use of this essential functionality, asks Jonathan Webb.

On both e-commerce and shopping comparison sites, users can find products in two different ways: searching and browsing. Searching obviously means using the site search, whilst browsing involves drilling down through the categories provided by the website.

Regardless of which method is used, users will be presented with a product listing from which to find the product(s) they want. This product listing can contain tens, hundreds or even thousands of products, so finding the right product from this list can be a difficult or even impossible task on any e-commerce site.

Getting sorting and filtering right improves findability and allows users to find the product they want in less time, from this product listing. If users can't find the exact product they require in the minimal time, there's a good chance they'll go to an e-commerce site where they can.

What is sorting and filtering?

Sorting is a method of changing the order of any product listing, where by users can choose which criteria they want the products to be listed by. So, price-conscious web users may choose to list the products in order of price, from cheapest to most expensive.

Filtering is a way of reducing the number of products in a product listing. Users choose which criteria are important to them and view only relevant products. For example, price-conscious users may choose to view only products for under £10 (thereby filtering out all products over £10).

Sort by options

Bringing products with certain criteria to the top of the page can be particularly useful for users who aren't exactly sure what they want. This is especially true if there are a large number of products in the product listing. (Product listings, or a list of products, can be found either by running a search or browsing through the available categories.)

The Waterstones website, for example, provides extensive options to sort its search results. As well as basic sort by options (e.g. 'Alphabetical: A-Z') the site also tailors its sorting to the fact that it's an online e-commerce bookshop. Users may find it helpful to sort by 'Bestselling', 'Publication date' or 'Average customer review'. The latter is an increasingly popular way of choosing products on the web due to its independent nature.

The language of the options is also plain and simple. For example, 'Price: Low to high' is used instead of 'Price ascending', the former being slightly less ambiguous.

Presenting sort by options

Utilising a dropdown menu for sorting uses up minimal screen space and is generally familiar to users of e-commerce sites. It does however 'hide' some of the options as they're not all visible at first glance.

You could instead offer sort by options as radio buttons. The main advantage of using radio buttons is that all sort by options are visible to users at one glance. Also, there should be less need to abbreviate terms as options aren't confined to the width of the dropdown field.

As a rough guide, if you offer users four or more sort by options, use a dropdown box. Three or less sort by options then use radio buttons as the options won't be 'hidden' in a dropdown box. Do be sure to restrict radio buttons to one row for easy scanning.

Filtering within product listings

Due to historically poor search results within websites, users are sometimes wary of site searches and will often browse through e-commerce sites to find a product. (They'll then use the search function only if they can't find what they're looking for). For users that are browsing in order to find a product, filtering within a category is crucial to enhance product findability.

Filters let users reduce the number of items within any product listing, by filtering out products that don't conform to specific criteria. This is often more useful for users who have a certain level of knowledge about the product(s) they require.

Dell offers a number of filtering options for their computers with a wide range of specifications. The product filtering concentrates on the technical specifics and usage but also has the option to 'View all...', thereby catering for all users. Filter options must be specific to each product listing and shouldn't be generically applied across the site.

Using filtering to influence a purchase

Filtering can also be useful when there are many different parameters to a product and can be used as a tool to persuade and influence a purchase. H.Samuel, for example, uses an extensive filtering system for their range of watches. The product listing uses commonly-used filters such as 'Price', which many users will be familiar with. It also uses other, more clever filters, such as 'Occasion: Anniversary, Christmas, Love, Good luck...' and 'Who is it for: For boys, For father, For groom, For bride...'.

These additional filters 'humanise' the online shopping experience matching users' real life expectations and requirements. They essentially create an online 'shop assistant', matching users' needs with specific products.

Speak users' language

Do be sure to employ sorting and filtering across all product listings on any e-commerce or shopping comparison website. The options you provide for both should speak users' language and be specific to the actual product listing (and not generically applied across the site).

Sorting and filtering are essential for helping users to find the products they're looking for. Users' increasing levels of sophistication when shopping online means they're likely to 'flick' between similar sites in a matter of seconds. Providing effective sorting and filtering for product listings can play a major part in helping users find (and ultimately buy) the product(s) they're looking for.

About the author
Jonathan Webb works for Webcredible. His work includes conducting focus groups and intranet usability projects.