Faceted Search: An Overview

Faceted Search: An Overview

What is faceted search?

Facets, also called smart filters, are a type of search filter that are used to help customers narrow down their search results quickly. Unlike static filters that are the same for every search, facets are dynamic — they can change depending on the context of the search query.

For example, an on-site search for “computers” would return very different filtering options than a search for “shoes.” Shoes might contain a gender result set (men’s or women’s) and computers might have a facet for “storage.”

Dynamic filters, or facets, can change depending on the context of the search query.

Facets have the ability to impact your overall site conversion rate and can make a big impression on customer perception and end user experience.

In this article, we’ll walk you through when to use a filter or a facet for site search, the types of facets you can create, how to add facets with Sajari, and some faceted navigation best practices.

When do you use facets, filters, and sorting?

Filters and search facets narrow down to relevant results. Sorting helps visitors reorganize results in ascending or descending order.

An example of static and dynamic filters.

Filters are commonly used to narrow down results based on broadly defined categories. Unlike facets, filters do not change between searches. In clothing stores for example, the main navigation often includes filters for gender or broad categories like "Clothing, Accessories, Shoes". Once selected, these filters can be applied in the background for subsequent searches, ensuring only results for the selected gender are returned.

Sites with more homogenous content can have fewer filters and may not need faceting.


What types of search facets are possible?

You can create a facet from almost any attribute on your site. Some of the more popular facets can include:

  • Category
  • Color
  • Price range
  • Size
  • Rating
  • Age

Let’s look at a few and how they might be formatted.

Category

Categories can be just about anything. Facet values can often be generated using a site’s URL structure. For example, your site may have a URL structure and category hierarchy such as:

  • Index > clothing > dresses
  • Index > clothing > shoes
  • Index > jewelry > necklaces > lockets
  • Index > jewelry > bracelets > charms

Color

Zappos not only allows you to filter by color, but also previews the number of results.

Filtering by color is really useful on retail sites for helping customers narrow results by color-preference. Facets can be created if you store color metadata in your index. If you don’t have the color data readily available, it can be created for you!

We’ve used the Google Vision API to automatically extract color and other metadata from images as they’re being indexed, which can then be used to design search filters and facets. Now, anytime new products are added to the site, the API will automatically extract the color data for use in filters.

Other facet types

Product shape?!? There’s really no limit to the kinds of filters and facets you can add to your site.

Age, rating, size, shape… there’s really no limits to the types of different facets you can add to a site. Keep in mind that facets can also take a lot of forms — as checkboxes, tabs, sliders, tag clouds, and more.

How do you create search facets?

If you have hundreds or thousands of products on your site, creating filters and facets may seem daunting. How can you possibly generate all possible filters for all your categories and products?

For our customers, faceted search can be created automatically. Sajari will infer the filters and facets available for your data — all you have to do is name them, pick a type of facet (list, select, tab, rating, etc.), decide where they should be placed on the results page or search overlay, and select other relevant options for your site search design. You can also manually add a facet by hand-selecting the attributes you want to filter on your site.

You might also use tagging, product descriptions, page titles, or other attributes to generate the additional data that can be used to improve search results and make it easier to generate facets.

Learn more about the Sajari search interface builder to design facets.

What are best practices for faceted search?

Here’s an example of category filters (along the top) and using tags (along the right side) to filter results.

Search facets can greatly improve site usability and customer experience. There are a few design tips worth noting that can improve, or hurt, facet design.

Design for your customers

The best rule of thumb is to always design for your customers. It applies to facets, too. Not just the visuals, but the whole experience.

  • Facet naming: You can create facets to filter by brand, category, gender, etc., but you can name them whatever you want. Is your audience and your brand more edgy or sophisticated? “Brand” could be named “Make” or “Category” could be called “Genre” — it depends on how you want to position it for customers.
  • Number of facets: Too many facets could be overwhelming to buyers; too few might be frustrating. Find the balance that perfectly matches audience needs with your collections.
Despite the trend to put different facets above results, two of the world's largest online marketplaces, Amazon and eBay, have (mostly) kept facets along the left side of the page.
  • Top or side: Putting facets along the left hand side of your search results is standard. Putting them above search results is trendy. It’s up to you, of course, but it is worth spending time looking at the sites you enjoy visiting or shopping on to see what you like or dislike about the experience.
  • Top results: Another thing to keep in mind, too, is that the facets at the top of the list will get the most attention. According to research from the Nielson Norman Group, “As a good rule of thumb, consider placing the most general, high-level filter categories at the top of the list, and the more specific ones towards the bottom.”
  • Measure results: Are your filters and facets being used? Search and conversion metrics, heatmaps, and clickstream data can help you to measure and optimize search facets.

Mobile vs desktop design

Desktop and mobile facet design and behavior should differ. On the desktop, results can instantly refresh as users select different filters. However, the smaller screen size and often lower bandwidth available to mobile users makes instant search impractical, not to mention frustrating.

The appearance and behavior of a website's facets on mobile and desktop should differ. When users choose different filters on the desktop, results may immediately update. Because of the smaller screen size and frequently lower bandwidth, instant search is difficult — not to mention aggravating — on mobile.


For mobile users, it’s a better user experience to allow them to batch up facet selections before submitting and refreshing search results.

Breadcrumbs


After winnowing down results with facets, searchers may want to start over or try different selections. Having some kind of breadcrumb trail and/or reset feature is a smart user interface element to include.

Truncating and searching within facets

Sometimes there are too many filtering options within a facet to display them all. You may need to truncate the list as shown below. Clearly there are more brands to choose from, but they’re hidden until “See More” is clicked.

Note that the subset selections are not in alphabetical order. Moosejaw has ordered brands based on popularity — a smart user-centric and revenue-centric decision.

Another popular way to achieve a similar result is to offer search within a filter or facet. A search box within the facet, as shown in the example below, would be configured to search for brands within the result subset of “running shoes.”

It's a search within a search! Catch.com.au includes a Brand search feature in the filter area to help visitors narrow results.

Additional reading

Facets and filters are one of the most important features of any search platform and can greatly impact your conversion rate. They can make the difference between a good and bad search experience.

Find out just how easy it is to set up faceted search with Sajari. Sign up for a free 14-day trial or schedule a time to speak with one of our search engine experts.

For more reading on facets and filters, check out these links below:


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