# Troubleshooting GitHub Pages Jekyll "Page Build Failed" Error

> Debugging a generic unhelpful build error on my GitHub Pages Jekyll site.

- Canonical URL: https://ctrl-alt-rees.com/2018-09-11-github-build-error-page-build-failed-config-yml-comments.html
- Published: 2018-09-11
- Last updated: 2020-01-22
- Author: Rees (ctrl-alt-rees)
- Licence: CC BY-SA 2.0 UK (https://creativecommons.org/licenses/by-sa/2.0/uk/), unless stated otherwise below

## AKA "We're not rebuilding your site and we're not telling you why"

This site is hosted on GitHub Pages, an excellent free service that runs on Jekyll.

I recently pushed an update to change the permalink structure and got an email with a generic "page build failed" error, with a completely unhelpful link to GitHub's documentation. After some Googling I was still stuck so by trial and error I undid various changes and re-committed until the site built OK again.

The issue? I had a commented out line in my _config.yml:

```yml
name: ctrl.alt.rees
# permalink: /:year-:month-:day-:url.html
permalink: /:year-:month-:day-:slug.html
highlighter: rouge
google_analytics: UA-71346066-3
url: "https://ctrl-alt-rees.com" # Base URL for sitemap generation
plugins:
- jekyll-sitemap
```

For some reason Jekyll will happily build this locally but GitHub Pages doesn't like it - despite the fact that it seems perfectly happy with the other comment further down the same file.

Answers on a postcard, please.