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Preview links show you a variant on a specific page. Forced variation goes further: it pins you into a variant for a full session, across every page you visit on the site.
Forced Variation tab

Preview modal → Forced Variation tab.

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When to use it

  • Walking a stakeholder through the site. Preview URLs show one variant on one page; forced variation lets them click around in the variant across the whole site.
  • QA on multi-page flows. Send yourself into Variant B, then click through the entire funnel to make sure nothing breaks downstream.
  • Debugging an issue reported for a specific variant. Pin yourself in and reproduce.

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How

The Preview modal has a Forced Variation tab. Pick an experiment, pick a variant, click apply. A session cookie is written on your domain that tells the snippet “always pick this variant for this experiment, for the rest of this session”. You can pin yourself into multiple experiments at once, each is a separate row in the tab.

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What “session” means

  • Ends when you close the browser, or after one hour, whichever comes first.
  • Does not survive a browser restart.
  • Applies only to the browser you set it in, not across devices.
Deliberate short-lived: forced variation is a QA tool, not a long-lived state. Nobody should be locked into a variant for their next real visit.

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What it does not do

  • Does not affect your results. Forced-variation exposures are suppressed the same way preview exposures are, no beacon lands, no MTU is counted.
  • Does not override the visitor opt-out URL. If you have opted yourself out with ?abtestly_optout=1, forced variation cannot bring you back in. Deliberate; opt-out is a user-respect feature and QA does not get to bypass it.
  • Does not apply to visitors other than you. Forced variation is per-browser, per-session, sharing your session cookie would not even do it (the cookie is scoped to your browser instance).

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Ending it

  • Close the browser (or wait an hour).
  • Or return to the Forced Variation tab and click Clear.
Clearing removes the cookie. Next pageview you are back to real bucketing. If you just want to send a colleague a shareable “here is Variant B on the pricing page” URL, use the preview link it does not need any setup on their side. Forced variation is for sessions you drive yourself.