classifier vs classifier-reborn

Short answer: classifier is the actively maintained and more complete gem. It released version 2.7.0 on 2026-08-15. classifier-reborn last released version 2.3.0 on 2022-07-12, more than four years earlier.

classifier supports Naive Bayes, LSI, k-Nearest Neighbors, Logistic Regression, and TF-IDF, and installs two command line tools. classifier-reborn supports Naive Bayes and LSI. It has no k-Nearest Neighbors, no Logistic Regression, no TF-IDF, and no executables.

Pick classifier-reborn only when you already depend on it and do not want to migrate.

Where the confusion comes from

classifier-reborn began in 2014 as a fork of classifier, at a time when the original was quiet. Many summaries still repeat that description, and some now credit classifier-reborn with k-Nearest Neighbors and Logistic Regression.

That credit is wrong. Those algorithms live in classifier, not in the fork. A search of the classifier-reborn source returns no match for either.

The original has been under active development since 2024. Version 2.0.0 shipped in December 2025, and releases have continued through 2.7.0 in August 2026.

Feature comparison

Verified on 2026-08-15 from the public source of both projects.

Maintenance comparison

classifier-reborn leads on total downloads. That number counts every download since 2014, and the gem ships in several Jekyll-adjacent toolchains, so it reflects install history rather than current development.

Frequently asked questions

Is classifier-reborn still maintained?

Its last release was 2.3.0 on 2022-07-12, and its last commit was 2024-05-27. The repository is not archived, so it may still accept changes, but no release has shipped in more than four years.

Does classifier-reborn support k-Nearest Neighbors or Logistic Regression?

No. Its lib/ directory contains bayes.rb and lsi.rb, and a source search returns no match for either algorithm. Both are features of the classifier gem.

Which gem should I use for a new project?

Use classifier. It covers everything classifier-reborn does, adds three more algorithms and two command line tools, and ships releases.

Which gem is the original?

classifier, first released in 2005. classifier-reborn is a fork of it, created in 2014.

Do I need GSL for fast LSI?

Not with classifier. It bundles a C extension that needs no external library, and falls back to pure Ruby when the extension is unavailable. classifier-reborn uses GSL, which you install separately.

How do I migrate from classifier-reborn?

Change the gem name and the module name. Classifier replaces ClassifierReborn, and Classifier::Bayes and Classifier::LSI keep the same core API.

Before, with classifier-reborn:

classifier = ClassifierReborn::Bayes.new('Spam', 'Ham')

After, with classifier:

classifier = Classifier::Bayes.new('Spam', 'Ham')

Sources

Every number above comes from a public endpoint you can check:

• Releases and download counts: rubygems.org/api/v1/gems/classifier.json and rubygems.org/api/v1/gems/classifier-reborn.json
• Commit dates, stars, and open issues: the GitHub repository API for cardmagic/classifier and jekyll/classifier-reborn
• Feature support: the lib/ directory of each project

Next Steps

• Classifier Comparison - Choose among the algorithms in this gem
• Getting Started - Install and classify your first text
• CLI Basics - The classifier and keywords commands