I just finished overhauling my tag system in Eleventy, and figured it was worth a quick write-up since there are a couple of gotchas — especially if you're mixing Markdown and Nunjucks.

Problem

I wanted clean URLs for tags, like /tags/journal/, and per-tag pages with a nice title.

I also wanted each tag page to have something like tag:devops as the title.

But when I tried adding title {{ tag }} to the front matter, I got [object Object] as the page title.

Solution

Turns out front matter fields like title: don't evaluate Nunjucks or Liquid. But permalink: does.

So instead, I discovered eleventyComputed:

eleventyComputed:
  title: "Tagged:{{ tag }}"

BAM Now I have dynamic titles in my tag page!