I judge each option using two questions before looking at the price. Does a test keep one destination URL, so an ad never has to be edited? Google's campaign editing guide explains what changes when you edit an ad. And does the page match what the ad promised, which Google scores as landing page experience?
I would shortlist the first three, then decide with a real test. Evan Miller's How Not To Run an A/B Test explains why you should fix the sample size before a test starts, and our split test sample size calculator works out how many visitors and how many days that requires.
1. Systeme.io
Best Carrd alternative for a free funnel behind the presell
Offers a free plan, or USD 17/mo.
I would choose Systeme.io when the presell needs a funnel, email and a checkout. It has a free plan. The one-page limit is on Carrd's own plan guide. See Carrd's plan guide.
Read the full Systeme.io review
2. Leadpages
Best Carrd alternative for server-side tests with no visit cap
Starts at USD 99/mo.
Leadpages is the builder for a server-side test, and none of its plans cap traffic. Google's landing page experience page is the reference for whether the ad and the page say the same thing. See Google's landing page experience guidance.
Read the full Leadpages review
3. Swipe Pages
Best Carrd alternative for fast mobile pages on paid traffic
Starts at USD 29/mo.
Most mobile traffic belongs on Swipe Pages. The same-URL test starts above its cheapest plan, and the review names that plan.
Read the full Swipe Pages review