Why your bounce rate suddenly hit 0% (or 100%)

A bounce rate that snaps to 0% or 100% is almost always a tracking fault, not a sudden change in how people use your site. The two extremes have two classic causes, and both are fixable once you know which you are looking at.

First, how GA4 defines it

In GA4, bounce rate is the inverse of engagement rate: the share of sessions that were not engaged (no 10-second stay, no conversion, no second page view). So anything that distorts engagement distorts bounce rate.

Bounce rate near 0% (everything looks engaged)

Usually a duplicate GA4 tag or an event firing repeatedly. Extra events make every session look engaged, so bounce collapses toward zero. It often appears overnight after a tag change, the same signature as conversions doubling.

Bounce rate near 100% (nothing looks engaged)

• The GA4 config tag fires but events do not, so sessions never register engagement.
• A broken single-page app setup where only the first view is tracked.
• Consent blocking everything after the initial hit.

How to fix it

Use GA4 DebugView to watch one session: count the events. Too many means a duplicate; too few means events are not firing. Fix the tag duplication or the event wiring and the bounce rate returns to something believable.

Datahound are analytics and ad-tracking specialists. We fix broken GA4, Google Tag Manager and server-side tracking so every sale, form and call gets counted. Back to datahound.agency · All tracking guides · Duplicate GA4 tags