- Add one line of code to your site to start running Optimizely experiments (A/B tests)
- Choose the pages where you'd like to add the Optimizely code snippet
- Find your project code snippet in Optimizely
- Decide where to add the code in your HTML
If this is your first time using Optimizely, you'll need to add a small snippet of code (here's how it works) to the <head> tag of your site's code to start running experiments. This snippet contains your unique Project ID and allows Optimizely experiments to run on your site. Once you add it, the snippet will update automatically; you don't need to do a thing.
After you complete the one-line implementation of the snippet with the three steps below, you'll be able to run experiments anywhere on your site.
1. Decide where to add the snippet
Consider the architecture of your site and experimentation program when deciding where to add the snippet. Each Optimizely project, or workspace, has its own snippet.
If your account plan includes cross-project events, you can track metrics across project spaces. If not, make sure that all parts of your site where you measure results are in the same project. One snippet should run across all those pages.
If you have separate development and production environments, or different domains and subdomains, you'll likely need separate projects (and snippets) for each.
2. Retrieve the snippet
Next, retrieve the snippet that you’ll add to your site. Here's a screenshot, with step-by-step instructions below:
Navigate to Settings > Implementation.
Click the Copy to Clipboard icon for the snippet you want to copy.
If your account uses custom snippets, you might see more than one snippet listed. Choose the one that's relevant to this part of your experimentation program.
Never have more than one snippet on your site at a time.
If you ever need to find your Project ID, it's the number immediately preceding the ".js" in the snippet URL.
3. Specify origins where Optimizely will run
An “origin” is a combination of a specific hostname, protocol, and port on your site. Tell Optimizely where you'll track events. By default, events that you track in Optimizely can only be used to target changes on the same origin, so enable cross-origin targeting to track events across origins.
4. Add your snippet to the <head> tag of your site
For optimal performance, add the Optimizely snippet to the <head> tag of the HTML for your site. We recommend implementing the snippet as high up in the head tag as possible, generally after your <html> tag, charset declarations, and possibly other meta tags. Place the Optimizely snippet before code for any analytics or heatmapping platforms as well.
Place these before the snippet:
Charset declarations and other meta tags, like <meta charset='utf-8'>
jQuery, if you're using your own version and not Optimizely's version (see jQuery Settings)
Place these after the snippet:
All other elements on your page
Any analytics or heatmapping code
Other content in a tag manager
Here's what the Optimizely snippet might look like on a page:
<!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!-- Add other meta information here --> <!-- Add stylesheets here --> <script src="https://cdn.optimizely.com/js/12345678.js"></script> <!-- Add scripts and other content here --> </head> <body>
Why in the top of the head tag? Optimizely works by making changes to your page as the page loads. If the snippet is added to the top of the head tag, then Optimizely will make changes to the page as it loads.
If the snippet is added anywhere lower, it will technically still work. But if the page has already loaded content that the visitor sees before the Optimizely snippet loads, the original version of the page may load before being transformed into the variation by Optimizely. This is known as "page flashing." In most cases, the code executes too quickly for this to be visible. But to avoid any potential problems we suggest adding the snippet as early in the execution path as possible.
Please don't modify the snippet. Copy and paste it onto your site exactly as you see it within Optimizely. Otherwise, Optimizely may not run correctly on your site.
You'll need the ability to add the snippet to the head tag of your production environment and development environments (if you have both).
By default, the snippet is loaded synchronously, which is recommended. However, if you need to load Optimizely asynchronously, read this article to learn to implement asynchronous loading.
Check that the snippet is implemented
Here's how to check that the snippet has been implemented on your page correctly.
Load Optimizely with a tag manager or into a CMS
We don't recommend that you load the Optimizely snippet through a tag manager.
Loading Optimizely through a tag manager can cause issues such as page flashing, where the original version of your page is briefly displayed to visitors before the Optimizely experiment. Google Tag Manager, for example, doesn't support synchronous loading. Tag managers can also cause issues with your analytics integrations. To deliver the best experience to your visitors, we strongly recommend that you implement Optimizely outside of a tag manager.
If you must load Optimizely through a tag manager, consider these pitfalls and implementation suggestions and reach out to your Customer Success Manager to discuss implications.
Here are some tag managers that customers have used: