Wednesday, February 12, 2014
Faceted navigation, such as filtering by color or price range, can be helpful for your visitors, but it's often not search-friendly since it creates many combinations of URLs with duplicative content. With duplicative URLs, search engines may not crawl new or updated unique content as quickly, and/or they may not index a page accurately because indexing signals are diluted between the duplicate versions. To reduce these issues and help faceted navigation sites become as search-friendly as possible, we'd like to:
- Provide background and potential issues with faceted navigation
- Highlight worst practices
Share best practices
In an ideal state, unique content—whether an individual product/article or a category of products/articles— would have only one accessible URL. This URL would have a clear click path, or route to the content from within the site, accessible by clicking from the home page or a category page.
Ideal for searchers and Google Search
Clear path that reaches all individual product/article pages
One representative URL for category page
One representative URL for individual product page
Undesirable duplication caused with faceted navigation
Numerous URLs for the same article/product
The same product page for swedish fish can be available on multiple URLs.
Numerous category pages that provide little or no value to searchers and search engines), as demontrated in the following table:
- No added value to Google searchers given users rarely search for "sour gummy candy price five to ten dollars".
- No added value for search engine crawlers that discover same item ("fruit salad") from parent category pages (either "gummy candies" or "sour gummy candies").
- Negative value to site owner who may have indexing signals diluted between numerous versions of the same category.
- Negative value to site owner with respect to serving bandwidth and losing crawler capacity to duplicative content rather than new or updated pages.
- No value for search engines (should have 404 response code).
- Negative value to searchers.
Worst (search un-friendly) practices for faceted navigation
Worst practice #1: Non-standard URL encoding for parameters, like commas or brackets, instead of
- Key-value pairs marked with
- Multiple parameters appended with
[ ]rather than
- Key-value pairs marked with a
- Multiple parameters appended with
While humans may be able to decode odd URL parameters, such as
,,, crawlers have
difficulty interpreting URL parameters when they're implemented in a non-standard fashion.
Software engineer on Google's Crawling Team, Mehmet Aktuna, says "Using non-standard encoding is
just asking for trouble." Instead, connect key-value pairs with an equal sign (
append multiple parameters with an ampersand (
Worst practice #2: Using directories or file paths rather than parameters to list values that don't change page content.
/c123/ is a category,
/s789/ is a
session ID that doesn't
change page content:
/gummy-candy/, changes the page content in a meaningful way:
URL parameters allow more flexibility for search engines to determine how to crawl efficiently.
It's difficult for automated programs, like search engine crawlers, to differentiate useful values
gummy-candy) from the useless ones (for example,
sessionID) when values are placed directly in the path. On the other hand, URL
parameters provide flexibility for search engines to quickly test and determine when a given value
doesn't require the crawler access all variations.
Common values that don't change page content and should be listed as URL parameters include:
- Session IDs
- Tracking IDs
- Referrer IDs
Worst practice #3: Converting user-generated values into (possibly infinite) URL parameters that are crawlable and indexable, but not useful in search results.
For example, user-generated values like longitude/latitude or "days ago" as crawlable and indexable URLs:
Rather than allow user-generated values to create crawlable URLs—which leads to infinite possibilities with very little value to searchers—perhaps publish category pages for the most popular values, then include additional information so the page provides more value than an ordinary search results page. Alternatively, consider placing user-generated values in a separate directory and then robots.txt disallow crawling of that directory.
User-agent: * Disallow: /filtering/
Worst practice #4: Appending URL parameters without logic.
Extraneous URL parameters only increase duplication, causing less efficient crawling and indexing. Therefore, consider stripping unnecessary URL parameters and performing your site's "internal maintenance" before generating the URL. If many parameters are required for the user session, perhaps hide the information in a cookie rather than continually append values like:
Worst practice #5: Offering further refinement (filtering) when there are zero results.
Allowing users to select filters when zero items exist for the refinement.
Only create links/URLs when it's a valid user-selection (items exist). With zero items, grey out filtering options. To further improve usability, consider adding item counts next to each filter.
Prevent useless URLs and minimize the crawl space by only creating URLs when products exist. This
helps users to stay engaged on your site (fewer clicks on the back button when no products exist),
and helps minimize potential URLs known to crawlers. Furthermore, if a page isn't just temporarily
out-of-stock, but is unlikely to ever contain useful content, consider returning a
404 status code.
404 response, you can include a helpful message to users with more
navigation options or a search box to find related products.
Best practices for new faceted navigation implementations or redesigns
New sites that are considering implementing faceted navigation have several options to optimize the "crawl space" (the totality of URLs on your site known to Googlebot) for unique content pages, reduce crawling of duplicative pages, and consolidate indexing signals.
- Determine which URL parameters are required for search engines to crawl every individual content page (for example, determine what parameters are required