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Relevanssi Finnish Base Forms

Latest Stable Version Build Status

Relevanssi plugin to add Finnish base forms into search index using Voikko.

What does it do?

This plugin allows you to add base forms of Finnish words in Relevanssi search index. For example for word koirillekin, tokens koirillekin and koira are saved in the index during indexing. Learn mode by reading this article (in Finnish).


API type

You can use bundled voikkospell binary (on a linux x64 system) to lemmatize the indexed terms.

There is also an option to use a system-wide voikkospell command line application if you have Voikko installed on your system.

It's also possible to set up an external Node.js API to access Voikko over HTTP. Using the binary or CLI application is much faster because it doesn't have the overhead of performing a HTTP request.

Special thanks to siiptuo for contributing voikkospell support for this plugin!

Add base forms to search query

Enable this option to add base forms to search queries entered by users.

Split compound words

Enable this option to split compound words during indexing (and for user queries if the above option is enabled). For example, the word kerrostaloille is transformed into tokens kerrostaloille, kerrostalo, kerros and talo in the search index.


  • Relevanssi 4.0.4 or later
  • PHP 5.5.9 or later
  • One of the following:
    • A x64 Linux server
    • A server with voikkospell command line application installed
    • A server with Node.js and about 1GB of spare RAM


  1. Download latest version from the releases tab
  2. Unzip the plugin into your wp-content/plugins directory
  3. Activate Relevanssi Finnish Base Forms from your Plugins page

Bundled voikkospell binary

  1. Go on the Plugins page, find the plugin, click Settings. For API Type select Voikko binary (bundled).

Voikkospell command line

  1. Install voikkospell on your server. On Ubuntu/Debian this can be done with apt install libvoikko-dev voikko-fi
  2. Go on the Plugins page, find the plugin, click Settings. For API Type select Voikko command line.

Node.js web API

  1. Install and start Voikko Node.js web API.
  2. Go on the Plugins page, find the plugin, click Settings and enter the Node API URL there

After installation, remember to re-index the site from Relevanssi settings page.