The organic sitelinks are the additional hyperlinks to the website subpages that appears under the Google search results listing. The sitelinks are the organic results by google itself through automated algorithm. According to the Google patents, sitelinks are derived from the user metrics, in particular, the number of times a page is visited, the amount spent on the page, bounce rate, content relevancy and other user behavior for that page.

The idea of the sitelinks extension are to make user-friendly result and helps users to navigate the site to the most popular and related pages or links within the website listed.

Basically, sitelinks appear when the site is ranked on the first position on the first page of the SEPRs and it is also said to appear on some search results where google thinks one result is far more relevant that other results like navigational or brand related search queries.

According to the google search console help,

We only show sitelinks for results when we think they’ll be useful to the user. If the structure of your site doesn’t allow our algorithms to find good sitelinks, or we don’t think that the sitelinks for your site are relevant for the user’s query, we won’t show them.

At the moment, sitelinks are automated. We’re always working to improve our sitelinks algorithms, and we may incorporate webmaster input in the future. There are best practices you can follow, however, to improve the quality of your sitelinks. For example, for your site’s internal links, make sure you use anchor text and alt text that’s informative, relevant, compact, and avoids repetition and overstuffing.

How to improve your organic sitelinks extension?

• Get a unique brand name and optimize to rank for the first position
• Identify more keywords opportunities to rank on the first position on SERPs
• Organize pages and relevant content through the easy navigation structure
• Optimize pages with unique and informative title tag and meta description.
• Focus optimizing your site for the users rather than robots.
• Find more opportunities through data analysis to promote and strategize so that more sitelinks appears on the search engine results page