Facts checked November 2026. Vendors change products and pricing; follow the links in Sources for current details.
What Optimizely is
Optimizely sells a digital experience platform that includes content management, commerce and experimentation. On the experimentation side there are two main products:
- Web Experimentation: client-side testing with a visual editor, for marketers and CRO teams changing pages in the browser.
- Feature Experimentation: server-side and app testing through SDKs, with feature flags and gradual rollouts, aimed at product and engineering teams.
Its statistics are handled by Stats Engine, which uses sequential testing and controls the false discovery rate. In practice that means you can watch results as they come in without inflating false positives the way repeated fixed-sample tests do.
Optimizely is aimed at mid-size and enterprise organizations. Pricing isn't published and is set through sales.
What ABFinal is
ABFinal is a free website with seven A/B testing calculators and two X post tools, plus guides. It doesn't run tests. It helps you decide whether a test is worth running, how long it needs, and how to read the numbers at the end. No account, no script on your site, nothing stored.
Side by side
| Optimizely | ABFinal | |
|---|---|---|
| Runs experiments on your site or app | Yes | No |
| Visual editor | Yes (Web Experimentation) | No |
| Feature flags and server-side tests | Yes (Feature Experimentation) | No |
| Statistics | Sequential, false discovery rate control | Fixed-sample z-test and chi-square, exact Bayesian probability |
| Sample size and duration planning | Built-in guidance | Dedicated calculators with formulas shown |
| SRM checking | Platform features | Standalone checker, any split |
| Price | Quote-based | Free |
| Setup | Snippet or SDK, onboarding | None |
When Optimizely makes sense
- You run many tests a month across web and product, and need governance, permissions and audit trails.
- Engineers want feature flags and server-side experiments in the same system.
- You want to monitor tests continuously without breaking the statistics.
- You have the budget for an enterprise contract.
When ABFinal is enough, or useful alongside
- You're deciding whether you have enough traffic to start testing at all. The MDE calculator answers that in seconds.
- You run tests through a cheaper tool or in-house code and need a trusted way to size and analyze them.
- You want a second opinion on a result, or to explain the math to a stakeholder with a formula you can show.
- You run Optimizely and want to check a sample ratio, or plan a test before setting it up.
A note on comparing their statistics
If you paste numbers from an Optimizely test into the significance calculator and get a different answer, that's expected. A sequential method is deliberately more conservative early in a test to pay for the freedom to look at any time. Neither number is wrong; they answer slightly different questions. When a test has run to a planned sample size, the two usually point the same way.
Common questions
Is ABFinal a free alternative to Optimizely?
Not for running experiments. ABFinal doesn't split traffic or change pages. It's free for the planning and analysis parts of testing: sample size, duration, split checks and significance. To actually run tests you need a platform such as Optimizely, another vendor, or your own implementation.
Why might Optimizely's results differ from ABFinal's significance calculator?
Optimizely's Stats Engine uses sequential testing with false discovery rate control so results stay valid while you monitor them. ABFinal's calculator runs a fixed-sample z-test, which assumes you analyze once at the planned end. On the same data the two can disagree, especially early in a test.
How much does Optimizely cost?
Optimizely doesn't publish list prices for its experimentation products; pricing is quoted by its sales team and depends on traffic and modules. Check with Optimizely for current terms.