1.9.x was the development (aka &quot;mainline&quot;) branch and 1.8.x was &quot;stable&quot;. Odd-numbered releases directly become the next stable. See the graphic here:<p><a href="https:&#x2F;&#x2F;www.nginx.com&#x2F;blog&#x2F;nginx-1-10-1-11-released&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.nginx.com&#x2F;blog&#x2F;nginx-1-10-1-11-released&#x2F;</a>