Four days in, one creative is clearly out front in the spreadsheet, so you shift the budget. A week later the gap has vanished and you cannot say whether you backed the right one or paid to learn nothing. Paste your numbers in here and you get a straight answer: the lead is real at 96% confidence, or it needs roughly 4,000 more impressions per variant before you call it.
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Every creative test ends the same way. Four variants, a column of percentages, and a decision that has to be made on Thursday. So you pick the top row. The trouble is that a difference between two rates is only meaningful once you have enough of them, and nothing in a spreadsheet will ever tell you when that moment arrives:
Enter what your ad platform already gives you: spend, impressions, clicks and conversions per variant. Everything after that is computed for you.
A two-proportion z-test runs between the current leader and every other variant on the metric you pick. You get “Winner: Variant B, 96% confidence, call it” or “No clear winner yet” — with the z-score and p-value underneath if you want to show your working to a client.
When the lead is not yet real, it tells you roughly how many more impressions or conversions each variant needs at current rates. That turns “let’s give it a few more days” into a number you can put in a status update.
CTR, CPC, CPM, conversion rate and CPA for each variant, plus ROAS as soon as you add a revenue-per-conversion figure. Sortable by any column, with the best value in each one highlighted so the trade-offs are obvious.
Log the same variant again in a few days and it tracks that variant’s CTR across every reading. When it drops more than 20% off its own peak you get a warning and a trend line, before the ad quietly stops working.
Tests are saved in your browser and listed on a dashboard with their platform, status and winner. Reopen a test from six weeks ago, add another reading, or clean up the ones that are done.
“Copy as Markdown” gives you a clean summary table and the verdict, ready to paste into a Slack update or an email. There is a full CSV of every variant across every test, and a JSON backup you can restore on another machine.
The same three variants, judged on CTR and then on conversion rate. One of those answers is a decision; the other is a warning.
| Variant | Spend | CTR | Conv. | CPA | ROAS |
|---|---|---|---|---|---|
| A — Founder to camera | $520.40 | 1.09% | 47 | $11.07 | 10.84× |
| B — Customer testimonial | $524.10 | 1.60% | 82 | $6.39 | 18.78× |
| C — Numbers on screen | $358.40 | 1.32% | 41 | $8.74 | 13.73× |
Illustrative figures from the built-in example test, not a screenshot of your data.
“The maths here is the same two-proportion z-test that every A/B testing platform runs behind the scenes. The difference is that it works on the numbers your ad platform already gives you, in a file you own, without a seat licence or a data pipeline.”
No subscription, no seats, no usage credits. You buy the tool and it is yours.
No. There are no API calls of any kind. You type or paste in the spend, impressions, clicks and conversions from whatever report you already look at. That is deliberate: no OAuth, no tokens to rotate, no access to your ad accounts, and it keeps working when a platform changes its API.
A two-tailed two-proportion z-test with a pooled standard error, on either CTR (clicks over impressions) or conversion rate (conversions over clicks). Sample-size guidance assumes 95% significance and 80% power. It compares the current leader against each other variant, one metric at a time.
In your browser’s local storage, on the device you are using. Nothing is uploaded and there is no server to hold it. That also means clearing your site data will delete it, so export the JSON backup if a test matters.
As many as you like, though the statistics get less reliable the more you run at once: with enough variants one will look like a winner by chance alone. Two to four per test is the sensible range, and the tool says so in the verdict panel.
Yes. The comparison table collapses into stacked cards on narrow screens, and it installs to your home screen as an app that runs offline.