WP Calais Archive Tagger

The Calais Archive Tagger plugin automatically goes through your archives and tags every post you’ve written. The plugin uses the Open Calais API to perform semantic analysis of your post text and suggest tags. If a post already contains a suggested tag, that tag isn’t added, but other new tags found are. It takes about 5 minutes to tag 200 posts.

Also see the Calais Auto Tagger plugin, which adds tag suggestion to your post writing screen. These two plugins work together to make tagging both new and past content simple, but can be used separately as well.

Calais Archive Tagger

The Calais Archive Tagger requires you have an Open Calais API key. Getting a key is easy as filling out two forms — it’s an instant, automated process. First, go to the Open Calais site and use the “Register” link at the top of the page to create an account. Then, request an API key by filling out this form. Enter your API key on the Calais Configuration tab of your plugins page.

Calais Archive Tagger is compatible with WordPress 2.3+ and WordPress 2.5+ blogs. It is free for personal and commercial use, but may not be redistributed without permission. Please e-mail me if you want to do that.

Current Version

Version: 1.4
Release Date: 3/23/2009
Download: WP Calais Archive Tagger at the WordPress Codex

Version 1.1 adds a rate limiter (2 posts processed per second) to ensure you don’t exceed the Calais API rate limit (2 requests per second and 40,000 requests per day). I’ve also wrapped the API call in a try/catch block so any exceptions won’t result in a loop condition. Version 1.2 adds a check to make sure old tags are never lost when adding new ones, and no longer adds e-mail addresses found as tags.


I recommend backing up your WordPress database before using this for the first time. There is no risk of damaging the database, as this plugin uses WordPress API functions to add the tags (no direct database access), but if you’re not happy with the tags it adds, you may want the ability to undo the additions easily.

This plugin relies on the Open Calais Tags PHP class, which requires PHP 5 web hosting with PHP’s cURL extension enabled (the majority of web hosts). Also see my blog stats plugin for W3Counter.


Unzip the archive and upload the files to your wp-content/plugins directory. Then activate the plugin from the plugins tab of your WordPress administration area. You’ll now have a “Calais Archive Tagger” link on your plugins menu where you can enter your API key and start the tagging process.