This system already exists, although it's manually done. Basically any content that matches this list are entirely excluded from search: https://github.com/wikimedia/mediawiki/blob/master/includes/content/WikiTextStructure.php#L29-L40

	private $excludedElementSelectors = [
		// "it looks like you don't have javascript enabled..." – do not need to index
		'audio', 'video',
		// The [1] for references
		'sup.reference',
		// The ↑ next to references in the references section
		'.mw-cite-backlink',
		// Headings are already indexed in their own field.
		'h1', 'h2', 'h3', 'h4', 'h5', 'h6',
		// Collapsed fields are hidden by default so we don't want them showing up.
		'.autocollapse',
	];

Items that match this list are moved from the 'text' field into an auxilliary field: https://github.com/wikimedia/mediawiki/blob/master/includes/content/WikiTextStructure.php#L45-L56

	private $auxiliaryElementSelectors = [
		// Thumbnail captions aren't really part of the text proper
		'.thumbcaption',
		// Neither are tables
		'table',
		// Common style for "See also:".
		'.rellink',
		// Common style for calling out helpful links at the top of the article.
		'.dablink',
		// New class users can use to mark stuff as auxiliary to searches.
		'.searchaux',
	];

The currently suggested plan would be to mark something with the 'searchaux' class. The auxilliary text is indexed and searched, but with a low value. We could add a selector to the exclude list as well if needed?

In T162905#3179037, @EBernhardson wrote:

We could add a selector to the exclude list as well if needed?

Yes.
"searchaux" is different from the need to absolutely exclude, because it is targeting useful elements that may help for the search. Navigation items are elements that are not supposed to be taken into consideration at all. IMHO.

Change 348855 had a related patch set uploaded (by EBernhardson):
[mediawiki/core@master] Allow editors to exclude navigation items from search indices

https://gerrit.wikimedia.org/r/348855

Change 348855 merged by jenkins-bot:
[mediawiki/core@master] Allow editors to exclude navigation items from search indices

https://gerrit.wikimedia.org/r/348855

We should find a place to document this new selector, we have https://www.mediawiki.org/wiki/Help:CirrusSearch but I'm not sure this page is well known by editors. @Trizek-WMF any suggestions?

@dcausse, Help:CirrusSearch is the right place to document and User-notice the best way to communicate it. But @CKoerner_WMF will have more ideas than me about it. :)

I think Help:CirrusSearch makes sense. @Cpiral, assuming you agree I'd love your opinion on where in the documentation. :)

How would phrase this in a couple of simple sentences for non-technical readers?

In T162905#3257112, @Johan wrote:

How would phrase this in a couple of simple sentences for non-technical readers?

How about something like "You can now tag navigation elements like hatnotes to not appear in search result snippets"? That does include a few technical terms, but it might be understandable to the Tech News audience. What do you think?

I'll probably simplify it, but I can work with that. Thanks! (:

In T162905#3258212, @Johan wrote:

I'll probably simplify it, but I can work with that. Thanks! (:

Great. Thanks!

Just ping me when you know when this will go into production.

It looks like this section was added to the documentation, for this new feature:
https://www.mediawiki.org/wiki/Help:CirrusSearch#Exclude_content_from_the_search_index

I suggest adding more details, explaining things like

• How it gets added to a template (e.g. searchaux)
  • And how it gets added to a Lua module (?!)
• How it impacts the search results
  • E.g. I searched enwiki for insource uses and I see one instance currently.
  • IIUC, that searchaux is pushing the results down for "Carboniferous Rainforest Collapse", if the instances just include the template Template:Carboniferous_graphical_timeline and not the plain text within the prose.
• 1 or 2 examples of things that we should use each wthin, and where we should NOT use each)
  • i.e. I'm unsure where exactly class="navigation-not-searchable" would ever be used (perhaps the entire 'module:mbox' family?), or if it might have negative consequences that should be kept in mind?
  • i.e. I would hesitantly guess that class="searchaux" should be added to Module:Navbox but I'm not sure (and 6million page uses, so...)
• How it relates to other CSS classes, such as
  • class="metadata" which I see used in Module:Navbox/configuration -- Note: AFAIK The only documentation about that class is in the very outdated https://en.wikipedia.org/wiki/Wikipedia:Catalogue_of_CSS_classes#Classes - I don't know if that's a global standard already, or if each wiki has invented their own?
  • class="noprint" which is used in things like the `<languages/> bar.
  • Possibly class="navigation-not-searchable" is either redundant to one of those, or has an overlap but subtle difference (which would need to be explained).

Thanks!!

In T162905#3309085, @Quiddity wrote:

It looks like this section was added to the documentation, for this new feature:
https://www.mediawiki.org/wiki/Help:CirrusSearch#Exclude_content_from_the_search_index

Good! Gotta start somewhere.

• How it relates to other CSS classes, such as
  • class="metadata" which I see used in Module:Navbox/configuration -- Note: AFAIK The only documentation about that class is in the very outdated https://en.wikipedia.org/wiki/Wikipedia:Catalogue_of_CSS_classes#Classes - I don't know if that's a global standard already, or if each wiki has invented their own?
  • class="noprint" which is used in things like the `<languages/> bar.
  • Possibly class="navigation-not-searchable" is either redundant to one of those, or has an overlap but subtle difference (which would need to be explained).

The metadata class is mostly documented in https://www.mediawiki.org/wiki/Help:Extension:Media_Viewer#How_can_I_disable_Media_Viewer_for_unrelated_images.3F, I think. It would indeed be useful to have a single index for such classes, perhaps within https://www.mediawiki.org/wiki/Manual:Interface/IDs_and_classes . There's also nomobile, which has an unclear overlap with noprint.