<b>Layout Testing Tools: Trust Only Randomized-Per-User</b>

<b>Layout Testing Tools: Trust Only Randomized-Per-User</b>

Reviewing the category itself. Tools like Ezoic, Snigel, or homemade GAM splits all 'test layouts' — but the ones that randomize per pageview lie to you.

What it does — serves layout A or B and reports RPM by variant.
Setup effort (varies) — the discriminator is the bucketing unit, not the UI.
RPM lift seen — per-user randomization gives trustworthy reads; per-pageview tools inflate 'winners' because heavy users (high RPM anyway) get re-randomized constantly.

Pros — proper tools find real +5-15% layout wins.
Cons — per-pageview tools (more common than you'd think) produce noise you'll chase for weeks.

Lift: ★★★★☆ — Risk: ★★☆☆☆
Best for: anyone evaluating a layout-AB vendor. Ask 'what's the randomization unit?' first. Skip any tool that can't answer.