Channel-specific metrics and guardrails
Each campaign has one primary metric that drives the verdict. The available primary metrics depend on the channel you select. All other metrics are tracked as secondary/diagnostic metrics for context.
Primary metrics by channel
| Metric | Push | SMS | In-app | |
|---|---|---|---|---|
| Open rate | Yes | No | No | No |
| Click rate | Yes | No | Yes | Yes |
| Tap rate | No | Yes | No | No |
| Conversion rate | Yes | Yes | Yes | Yes |
| Revenue per exposure | Yes | Yes | Yes | Yes |
Attribution methods
Email and SMS use URL-based attribution: liftstack embeds a tracking parameter (lf_cid) in links and matches click events back to the variant.
Push and in-app channels use profile-based attribution: since liftstack writes variant assignments to user profiles, any engagement event from that user within the attribution window is attributed to their assigned variant. No URL tracking parameters are needed.
Open rate and Apple Mail Privacy Protection
Open tracking is unreliable because of Apple Mail Privacy Protection (MPP) and email client pre-fetching. These technologies automatically trigger “opens” for every email, whether or not the recipient actually looked at it. Absolute open rate numbers are inflated, but relative comparisons between variants remain valid because the noise affects all variants equally.
Safety guardrails
Even if a variant drives conversions, it might be doing so in a way that damages your list health. liftstack monitors three guardrail metrics automatically:
- Unsubscribe guardrail. If the winning variant’s unsubscribe rate is meaningfully higher than the control’s (more than 0.1 percentage points), the system blocks the winner declaration.
- Complaint guardrail. If the variant triggers a meaningful increase in spam complaints (more than 0.05 percentage points vs the control), the winner is blocked.
- Bounce guardrail. If the variant causes a meaningful increase in email bounces (more than 0.5 percentage points vs the control), the winner is blocked.
These guardrails apply to email campaigns. For push and SMS channels, liftstack monitors opt-out rates to protect your subscriber lists.
A variant that triggers a guardrail violation will not be declared a winner, even if it has a high probability of being best on the primary metric.