Asumaru

“Multisite Language Switcher” is very attractive plugin. 
However, It may not be available for your site plan.
<ul>
<li>Site A (English) example-site.com/</li>
<li>Site A (Japanese) example-site.com/jp/</li>
<li>Site B (English) example-site.com/siteB/</li>
<li>Site B (Japanese) example-site.com/siteB-jp/</li>
<li>Site C (English) example-site.com/siteC/</li>
<li>Site C (Japanese) example-site.com/siteC-jp/</li>
</ul>
“Multisite Language Switcher” cannot tell the difference between site A, site B and site C. 
Therefore you cannot connect the language when there are site A, site B, site C.
“MSLS Grouping” adds “group_key” to settings of “Multisite Language Switcher”. 
For example, you set “group_key” with “SiteA” or “SiteB” or “SiteC”. 
You can limit a language site in a group by doing this plugin. 
You can display only the first site when there are multiple same language sites in a group.
And, it provide shortcode “SameLangSites” and widget “SameLangSites”. 
You can output the list of different groups of the same language. 
For example, “SameLangSites” of “site A (English)” lists ” site B (English)” and “site C (English)”.
<ul>
<li>Site A (English) => Site B (English), Site C (English)</li>
<li>Site B (Japanese) => Site A (Japanese), Site C (Japanese)</li>
</ul>
And, it provide “Language” column on the Table of Sites in network.
And, it provide “Language Flag” in Admin-Bar.

MSLS Grouping

You can multilingualize by "Multisite Language Switcher" with grouping the sites of the plural same languages.

ThemeBoy

Ayebare Mucunguzi Brooks

matthewtx

This plugin is designed to be used with Transifex localization platform. There’s no need to create one language per post, insert language tags, or have multiple WordPress instances. Your site’s content is automatically detected and ready to be saved to the Transifex localization platform, where you can translate with the help of your existing translators, or order professional translations from Transifex partners.
In order to use Transifex, you will need to <a href="https://app.transifex.com/signup/?utm_source=wp-directory&utm_campaign=int-wp" rel="nofollow ugc">sign up here for an account</a>. This plugin also requires a Transifex Live API key. More information about how to obtain a key can be found in the <a href="https://help.transifex.com/en/articles/6261241-wordpress#h_2339ce4961" rel="nofollow ugc">plugin documentation</a>.
Features:
<ul>
<li>Integrates Transifex into WordPress</li>
<li>Adds support for localized language URLs either by subdomain or subdirectory.</li>
<li>Adds support rewriting all URLs on the page</li>
<li>Automatically adds hreflang tags to your pages.</li>
<li>Adds supports for using an external prerendered server for SEO purposes</li>
<li>Works with WordPress multisite</li>
</ul>
Learn more about the <a href="https://www.transifex.com/integrations/wordpress/?utm_source=wp-directory&utm_campaign=int-wp" rel="nofollow ugc">Transifex Live Translation Plugin</a>.
Get Involved:
Developers can contribute via the plugin’s <a href="https://github.com/transifex/transifex-live-wordpress" rel="nofollow ugc">GitHub Repository</a>.
Translators can contribute new languages to this plugin or our other WordPress plugins through <a href="https://explore.transifex.com/wp-translations/transifex-live/?utm_source=wp-directory&utm_campaign=int-wp" rel="nofollow ugc">Transifex</a>.
Minimum Requirements:
<ul>
<li>WordPress 3.5.2 or greater</li>
<li>PHP version 5.4.0 or greater</li>
<li>MySQL version 5.0 or greater</li>
</ul>
<h3>Tips for developers</h3>
The Transifex Live plugin uses WordPress hooks to manipulate the links found in your website’s content, so they always point to the appropriate language. If you use custom post types (or one of your plugins does) that emits the ‘the_content’ filter, our code might not be triggered.
For those cases, it is recommended to manually trigger our custom filter ‘tx_link’ before you return your content, as seen in the example below:
Ex. $updated_content = apply_filters(‘tx_link’, $original_content);
It is also recommended to use <a href="https://codex.wordpress.org/Widgets_API" rel="nofollow ugc">widgets</a> in your theme instead of custom code, since this allows you to make your integration more future proof against incompatibilities with 3rd party modules.

International SEO by Transifex

Transifex have done an outstanding job reimagining how we translate content for the web with their Transifex Live service. I am proud to have contributed to the code early on and to see it continue to grow. It not only saves hours of time when compared to other translation methods, but also integrates with one of the most powerful and intuitive localization platforms I have ever seen.



A must-have for multilingual WordPress sites

Translate your WordPress powered website using Transifex.

MSLS Grouping vs International SEO by Transifex