Feuerfest

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Adding canonical links for category and tag pages in Bludit 3.16.2

  • January 19, 2026 •
  • IT •
  • Christian

Google's Search Console has problems with my site regarding duplicate content due to "Duplicate without user-selected canonical". Which is Google's wording for:

The automatically generated site-views for your categories and tags have the same content sometimes. Hence identical content is available under different URLs.

And yes, when I checked the HTML source of these pages there is no canonical link. Despite the canonical-plugin being active.

A single post shows the following:

<!-- Load Bludit Plugins: Site head -->
<link rel="canonical" href="https://admin.brennt.net/please-don-t-remove-your-comment-section">
<link href="/bl-plugins/prism/css/prism.css" rel="stylesheet">

But for https://admin.brennt.net/tag/2fa or https://admin.brennt.net/category/it it only showed the following:

<!-- Load Bludit Plugins: Site head -->
<link href="/bl-plugins/prism/css/prism.css" rel="stylesheet">

ChatGPT to the rescue! - But with a twist!

As it is currently 6am I wasn't in the mood to dig through the code myself. So I asked ChatGPT: "How do I retrieve the tag name element in the Bludit blogging software". Only for ChatGPT to give me an extensive answer. ... For PHP-Code the canonical-plugin didn't have.

Ah.. Yes.. Typical, isn't it? Stupid LLMs, bla bla.

No, turns out on January 15th the canonical-plugins was extensively re-written. Fixing the missing canonical links. Great. So ChatGPT did indeed based it answer on the current code. I quickly searched the Bludit forum and GitHub if there is anything said about a new Bludit release but nothing showed up. And as the last release was in August 2024 I currently don't have high hopes for a release in the near future.

Instead I just copy & pasted the current code completely into ChatGPT - as providing the GitHub link didn't work - and got an answer that looked good.

<?php

class pluginCanonical extends Plugin {

	public function siteHead()
	{
		// Home page
		if ($GLOBALS['WHERE_AM_I'] === 'home') {
			return '<link rel="canonical" href="'.DOMAIN_BASE.'"/>'.PHP_EOL;
		}

		// Single page / post
		elseif ($GLOBALS['WHERE_AM_I'] === 'page') {
			global $page;
			return '<link rel="canonical" href="'.$page->permalink().'"/>'.PHP_EOL;
		}

		// Tag pages
		elseif ($GLOBALS['WHERE_AM_I'] === 'tag') {
			global $url;
			$tagKey = $url->slug();
			return '<link rel="canonical" href="'.DOMAIN_TAGS.$tagKey.'"/>'.PHP_EOL;
		}

		// Category pages
		elseif ($GLOBALS['WHERE_AM_I'] === 'category') {
			global $url;
			$categoryKey = $url->slug();
			return '<link rel="canonical" href="'.DOMAIN_CATEGORIES.$categoryKey.'"/>'.PHP_EOL;
		}
	}

}

The only new lines are the ones for tag pages and category pages.

Editing the bl-plugins/canonical/plugin.php file, reloading a category and a tag page, aaaaaaand we're green on canonical links:

<!-- Load Bludit Plugins: Site head -->
<link rel="canonical" href="https://admin.brennt.net/tag/2fa"/>
<link href="/bl-plugins/prism/css/prism.css" rel="stylesheet">

<!-- Load Bludit Plugins: Site head -->
<link rel="canonical" href="https://admin.brennt.net/category/it"/>
<link href="/bl-plugins/prism/css/prism.css" rel="stylesheet">

Great. Now back to the main problem...

Tag: Bludit