Since I had been using WordPress¹ before, after switching to Jekyll I naturally wanted to find a way to recognize <!-- more --> for truncating output.

Plugins

After a quick Google search, I found relevant plugins:

• jekyll-only_first_p: A plugin that outputs only the first paragraph requires Nokogiri support
• excerpt.rb: A plugin that recognizes <!-- more -->

However, if your Jekyll is also hosted on GitHub, you can’t use plugins. For security reasons, GitHub runs Jekyll with the --safe parameter, rendering all third-party plugins ineffective.

Liquid

Just when I was feeling a bit disappointed, I found this article: Post excerpts in Jekyll²

You can achieve this using a filter in the Liquid template language:

{{ post.content | split: "<!-- more -->" | first }}

Then add a Read More link after the truncated article:

<a href="#more>Read More →</a>

This way, even Jekyll hosted on GitHub can have truncated output.³

Notes added on 2018-10-10