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Before starting to use Nelio A/B Testing

There are some aspects you should take into account and check before starting to use Nelio A/B Testing to avoid possible configuration or compatibility problems.

Check Your Plugins Configuration

Cache/Optimizer Plugins

Nelio A/B Testing is compatible with cache/optimizer plugins. However, these plugins have an option to delay, defer, compress, and combine JavaScript files. This may usually be a good idea to speed up loading your site’s pages, but it tends to prevent Nelio A/B Testing from appending its tracking scripts.

If you’re using one of those, please make sure to exclude Nelio A/B Testing scripts from this optimization process (i.e. disable script minification, script combining, defer and async options, etc). Here is an example of how to do so if you are using OptimizePress. Other plugins might require you to specify the exclusions by name:

  • JavaScript nelio-ab-testing-main
  • Inline JavaScript nelio-ab-testing-main-js-before (which includes the nabSettings string in it)
  • Inline style nelio-ab-testing-overlay

Keep in mind that you may need to purge your cache and/or CDN if you use one after the changes. You may also need to purge them after starting/stopping tests, to make sure your visitors are served the latest version of your website where all the appropriate tests are running.

Security/Firewall Plugins

WordPress security plugins offer tools and functions to keep your website safe. Some of them can block Nelio A/B Testing plugin’s requests to our cloud and be the cause of it not working properly.

Nelio A/B Testing cloud runs on Amazon Website Services AWS and uses REST API, so check if there’s a setting in your plugin that allows you to exclude Nelio A/B Testing’s REST API (nab/api) to let us through such as to allowlist REST API endpoints.

SEO Plugins

Nelio A/B Testing poses no inherent risk to your site’s search rank as described here. However, some SEO plugins include a “Crawl Cleanup” feature that basically allows you to remove all unrecognized query arguments from visitor URLs and redirects them to the same page they were visiting without them. This helps prevent search engines from crawling every variation of your pages with all the unrecognized query arguments.

When Nelio A/B Testing tracking script runs, the first thing it does is check if the current page is under test. If it is, it performs a JavaScript redirection to a different URL that will include some testing parameters in your URLs (basically the original address with the additional query argument ?nab=x). These parameters tell Nelio A/B Testing which variant has to be loaded for each visitor.

To make sure that the redirect behavior works correctly with Nelio A/B Testing, in your SEO plugin settings, indicate that either the query arguments are not removed or create the exception to allow Nelio A/B Testing /^nab/ arguments.

Check Your Browser Configuration


We respect our customers and our customers’ visitors and value their data privacy. Nelio A/B Testing tracks only anonymous data and we don’t sell nor monetize your visitor’s data. Ever.

Nelio A/B Testing purpose is to help you understand how your visitors interact with your website.

Recently, some overzealous ad blocking tools have added our tracking domain ( to their list of URLs to block. Then, if a visitor is using an adblocker, Nelio A/B Testing can’t track their events by default. We believe these blocks are unwarranted for the reasons mentioned above.

If you’re worried about your actual visitors using adblockers not being tracked, there’s a setting in our plugin that lets you change the tracking URL. It’s called “Cloud Proxy.” You can read more about it in the link below: