Filtering search results

Tagged as: , , , , , , ,
 

The Design Need:

Users want to find an item in a large amount of content. Users often do not know exactly what their choice of items will be at the end of a search, e.g. if you are looking for a small, cheap camera, the choice will often depend on the offerings on the website.

Best Practice Examples:

Amazon uses a drill-down strategy to filter to the search resultsDynamic filters on www.kayak.com

Best Practice Solution:

The combination of free text search and filtering helps users to structure queries. Semi-structured queries provide access to structured and unstructured content. General guidance

  • Test, test and test again. Only by testing your result pages thoroughly with as much content as possible will you be able to match the result pages with the mental model(s) of your potential users.
  • Get to know the search terms entered by your users. Study the terms used by visitors to your site when they search your content.
  • Define search tasks based on user scenarios and personas derived from user analysis. These search tasks help to understand how users will search your site.
  • Each item should provide the user with the right “information scent”. Provide the right clues so that users can decide whether or not items will be what they are looking for.
  • Users are not looking for a showcase of what the site has to offer. When users perform a search they expect to get closer to the item they are looking for.
  • The goal is to show the most relevant results first. The most relevant result might differ for each user and situation. Offering sorting options helps to cater for these differences.

Some do’s and don’ts and things to keep in mind to help you design usable filtering for search results:

  • Choose where you place the filters in your layout in relation to the search results:
    • Left: the filters may not be recognized by less experienced users; the search results are placed in the centre of the page.
    • Top: all users easily notice the filters; the search results are pushed further down the page.
    • Bottom: the filters are easily overlooked and the user may only find them after scanning the first results page; the results are placed in the centre of the page.
  • Choose a suitable way to organize the filters, using one of three strategies:
    • Static order: best with a limited amount of filters that will always be visible to your users. A static order helps the user to build a mental model of the site.
    • Dynamically rank the order: best for large amounts of filters and if filters do not apply to all items in the content, e.g. megapixels apply for cameras but not for vacuum cleaners. Take care to choose the right filters for each situation.
    • Organize filters in groups: good for large amounts of filters that do not take up too much screen estate. Only possible if filters can be organized into groups.
  • Do not offer to many filters.
  • Don’t let users type ranges: they tend to over-constrain their queries. Provide good, suitable, predefined ranges; these will often differ according to the content/product types.
  • Choose the correct filter strategy:
    • Single filter, “drill down” strategy (links): good if you want the user to go down in a hierarchical structure.
    • Multiple filter, “parallel selection” strategy (check boxes): if an item can be selected based on multiple attributes.

      • In some cases these can be mixed, but you should be careful to use the right affordance for each type: check boxes indicate multiple select options.

  • Provide an “undo function” let users deselect filters or move back up in the hierarchy.
  • Do not let filters disappear during a search. You can collapse filters or show the selected filter values in a different way. Removing filters confuses the user and makes them loose overview.
  • Display only filter values that will deliver results.
  • Make sure that filter values cover all available content, e.g. a transparent candle holder will not show up when the colour filter is used if “transparent” is not a colour attribute.

Sorting
Sorting can help to put the most relevant information at the top of the search results. Sorting options will help your users if possible, particularly since sorting options will never deliver “no results”. Some dos and don’ts on using sorting:

    • Combining sorting and filtering can help users to find their way in content.
    • Do not hide your sorting options. If you offer sorting options, let users know that they have additional options available to obtain an overview of search results.
    • Providing search, sort and filter options in a phrase helps the user understand how it works: ‘Search: “Search term” in “Category” and sort by: “Sort option”’.
    • If the difference between sorting and filtering is not clear to the user it is best to combine them in one list and state clearly which options the user has without trying to explain the technical difference, e.g. a list with options such as “recently used” (a sorting option) and “bookmarked” (a filter option).

      When to use:

      When users have to make a selection from a large amount of content, when they are searching for a specific item in a large amount of content.

      You can only offer filter and or sorting options if the content that is being searched can be filtered or sorted according to specific attributes.

      More info elsewhere:

      • Categorized as Best Practices