While a theme experiment is live, previewing a theme takes one extra step. This explains why, and what to do.

Once a test is running, Cooee keeps every visitor on the version they were assigned. If a browser has remembered an earlier preview and starts serving a different theme, that visitor is put back. Keeping the two experiences separate is what makes the comparison trustworthy.

You are a visitor too. So if you open a theme preview on your storefront, Cooee sees you sitting on a theme that is not the one you were assigned and moves you back — the preview closes almost as soon as you open it.

Telling Cooee the preview is deliberate stops that happening.

The simplest option: open the experiment in Cooee and use the Preview button next to the theme you want to look at. Cooee knows the preview is yours and stays out of the way.

The preview lasts for that browser tab. Close the tab and you go back to browsing as a normal visitor.

If you would rather preview from Shopify, you need to add one parameter to the link so Cooee can tell it apart from an ordinary visit.

In Shopify Admin, go to Online Store → Themes. Instead of clicking Preview, right-click it and choose Copy link. Paste it into your address bar, add &cooee_theme_preview=on to the end, then press Enter. The result looks like this:

https://yourstore.com/?_ab=0&_fd=0&_sc=1&preview_theme_id=182075064699&cooee_theme_preview=on

You will stay on that theme for the rest of the tab, and can browse the whole store normally.

Clicking Preview directly in Shopify Admin will not work while a test is running. Shopify opens it in a way Cooee cannot tell apart from a normal visit, so you will be moved back to your assigned theme. Copy the link and add the parameter, or preview from Cooee instead.

Closing the tab is enough. To leave without closing it, visit your store with ?cooee_theme_preview=off on the end:

https://yourstore.com/?cooee_theme_preview=off

That returns you to your live theme and to browsing as a normal visitor.

While you are previewing, Cooee does not count you in the experiment. Your own browsing stays out of the numbers, which is what you want when you are clicking through both themes to compare them.

The trade-off is that preview mode is not the way to check your traffic split. Because assignment is switched off, you are not being placed in an arm at all. To see the split working, open a private window and browse as a fresh visitor — see Troubleshooting theme experiments.

Shopify may show a preview bar at the bottom of the page while you are previewing from Admin. Only you see it. Visitors assigned to the challenger theme never do — Cooee suppresses it for them, so the theme looks like a normal storefront.

If you are ever unsure whether you are looking at a preview or at what visitors see, open your store in a private window.