Related Content

Hugo uses a set of factors to identify a page’s related content based on Front Matter parameters. This can be tuned to the desired set of indices and parameters or left to Hugo’s default Related Content configuration.

List Related Content  

To list up to 5 related pages (which share the same date or keyword parameters) is as simple as including something similar to this partial in your single page template:

{{ $related := .Site.RegularPages.Related . | first 5 }}
{{ with $related }}
<h3>See Also</h3>
<ul>
	{{ range . }}
	<li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
	{{ end }}
</ul>
{{ end }}

Methods  

Here is the list of “Related” methods available on a page collection such .RegularPages.

.Related PAGE  

Returns a collection of pages related the given one.

{{ $related := .Site.RegularPages.Related . }}

.RelatedIndices PAGE INDICE1 [INDICE2 …]  

Returns a collection of pages related to a given one restricted to a list of indices.

{{ $related := .Site.RegularPages.RelatedIndices . "tags" "date" }}

.RelatedTo KEYVALS [KEYVALS2 …]  

Returns a collection of pages related together by a set of indices and their match.

In order to build those set and pass them as argument, one must use the keyVals function where the first argument would be the indice and the consecutive ones its potential matches.

{{ $related := .Site.RegularPages.RelatedTo ( keyVals "tags" "hugo" "rocks")  ( keyVals "date" .Date ) }}

Configure Related Content  

Hugo provides a sensible default configuration of Related Content, but you can fine-tune this in your configuration, on the global or language level if needed.

Default configuration  

Without any related configuration set on the project, Hugo’s Related Content methods will use the following.

related:
  includeNewer: false
  indices:
  - name: keywords
    weight: 100
  - name: date
    weight: 10
  threshold: 80
  toLower: false

[related]
  includeNewer = false
  threshold = 80
  toLower = false
[[related.indices]]
  name = 'keywords'
  weight = 100
[[related.indices]]
  name = 'date'
  weight = 10

{
   "related": {
      "includeNewer": false,
      "indices": [
         {
            "name": "keywords",
            "weight": 100
         },
         {
            "name": "date",
            "weight": 10
         }
      ],
      "threshold": 80,
      "toLower": false
   }
}

Note that if you have configured tags as a taxonomy, tags will also be added to the default configuration abve with the weight of 80.

Custom configuration should be set using the same syntax.

Top Level Config Options  

threshold

A value between 0-100. Lower value will give more, but maybe not so relevant, matches.

includeNewer

Set to true to include pages newer than the current page in the related content listing. This will mean that the output for older posts may change as new related content gets added.

toLower

Set to true to lower case keywords in both the indexes and the queries. This may give more accurate results at a slight performance penalty. Note that this can also be set per index.

Config Options per Index  

name

The index name. This value maps directly to a page param. Hugo supports string values (author in the example) and lists (tags, keywords etc.) and time and date objects.

weight

An integer weight that indicates how important this parameter is relative to the other parameters. It can be 0, which has the effect of turning this index off, or even negative. Test with different values to see what fits your content best.

pattern

This is currently only relevant for dates. When listing related content, we may want to list content that is also close in time. Setting “2006” (default value for date indexes) as the pattern for a date index will add weight to pages published in the same year. For busier blogs, “200601” (year and month) may be a better default.

toLower

See above.

Performance Considerations  

Fast is Hugo’s middle name and we would not have released this feature had it not been blistering fast.

This feature has been in the back log and requested by many for a long time. The development got this recent kick start from this Twitter thread:

Holy smokes! Build time dropped to 1.2 seconds!

— Scott S. Lowe (@scott_lowe) August 18, 2017

Scott S. Lowe removed the “Related Content” section built using the intersect template function on tags, and the build time dropped from 30 seconds to less than 2 seconds on his 1700 content page sized blog.

He should now be able to add an improved version of that “Related Content” section without giving up the fast live-reloads. But it’s worth noting that:

• If you don’t use any of the Related methods, you will not use the Relate Content feature, and performance will be the same as before.
• Calling .RegularPages.Related etc. will create one inverted index, also sometimes named posting list, that will be reused for any lookups in that same page collection. Doing that in addition to, as an example, calling .Pages.Related will work as expected, but will create one additional inverted index. This should still be very fast, but worth having in mind, especially for bigger sites.