ABTestly vs Optimizely, VWO, and Convert: a feature comparison
Optimizely, VWO, and Convert features compiled from their public developer docs in June 2026. Tools change, so check each vendor's site for current details.
Yes, we're ABTestly, so read this knowing who wrote it. We've kept the comparison at the feature level, where the differences are checkable against each vendor's own docs, and we've included an honest section on where each of the other three beats us, because they do.
The short version: Optimizely is the most capable and the most engineered, and priced for that. VWO is the gentlest on-ramp and the broadest all-in-one. Convert is the most transparent of the three on statistics and the most code-friendly. ABTestly is the most edge-native and code-first of the set: experiments are JSON in version control, served from Cloudflare's edge, with a fully published statistics methodology and a permanent free plan.
Feature by feature
| ABTestly | Optimizely | VWO | Convert | |
|---|---|---|---|---|
| Delivery | Cloudflare edge, 300+ cities; config served without an origin round-trip | Snippet loads synchronously, high in the head | SmartCode in async or sync flavours | Akamai CDN; synchronous by default |
| Anti-flicker | Scoped hide, no-flicker first paint; ~10KB gzipped runtime, loader under 1.5KB | visibility:hidden hide, removed after sync changes apply | Async shield (around 110ms in their docs) or sync; hide element is configurable | Built-in shield, synchronous by default |
| SPA / route changes | Per-site SPA mode; lifecycle re-runs cleanup-first on route change | Conditional activation plus waitForElement / waitUntil | Virtual page load API re-runs page matching | Re-evaluates on history.pushState; you undo your own DOM changes |
| Editor | Code / JSON only — no visual editor | Visual editor + Apply JS / Reset JS | Visual editor + code editor | Visual editor + five code editors |
| Test types | A/B testing | A/B, MVT, full-stack & feature flags | A/B, split URL, multivariate, multipage | A/B, split URL, multivariate, full-stack (Pro) |
| Stats engine | Two-proportion z-test, 95% CI on every lift, fixed-horizon (sequential on roadmap) | Stats Engine: always-valid sequential testing with false-discovery control | Bayesian SmartStats with a sequential option | Frequentist, sequential, or Bayesian — choosable per experiment |
| SRM detection | Yes — chi-square, flagged on the results card | Yes | Yes | Yes |
| Published stats methodology | Fully documented: how we count results | Documented | Documented | Documented (the most transparent of the three) |
| QA & debugging | Preview links and forced-variation URLs | First-class QA query params (force-bucket, disable, log levels, preview) | Preview mode and a debugger | Chrome debugger extension and a QA overlay across URLs and devices |
| Code in version control | Native — experiments are JSON, diffable and reviewable | Upload from a GitHub repo via a GitHub Action, plus REST API | REST API; default authoring path is UI-bound | REST API, a version-control widget, and an MCP server |
| Integrations | Native GA4 | GA4, Event API, and many more | Broad integration catalogue | 90+ integrations |
| Beyond A/B testing | — | Feature flags, full-stack experimentation, personalization | Heatmaps, session recordings, surveys, funnels | Heatmaps, personalization (Deploys) |
| Free option | Permanent free plan: 1 experiment, 3K MTU | No free plan (sales-led) | Free plan available, with paid tiers above it | 15-day trial (no card) |
| Pricing transparency | Published: free, then from $79/mo | Quote-based / sales-led | Tiered; entry pricing published | Published per tier |
Competitor rows summarise each vendor's public documentation as of June 2026 and are necessarily condensed; the linked vendor docs are the source of truth. The VWO ~110ms figure is VWO's own published average.
Where the others are genuinely better
- Optimizely is the most capable platform here: the most mature stats engine (always-valid sequential testing), first-class QA query params, deep feature-flag and full-stack experimentation, and a large enterprise tooling and integration footprint. If you need enterprise depth, it is hard to beat.
- VWO is the broadest all-in-one. Testing plus heatmaps, session recordings, surveys, and funnels in one product, with a gentle visual-editor on-ramp that a non-developer can drive. If you want one tool for the whole optimisation stack, VWO covers the most ground.
- Convert is the most transparent of the three on statistics, the most openly code-friendly (five code editors, project to variation scope), and has 90+ integrations plus a long, candid operating history. A strong pick when you want code access and statistical clarity from an established vendor.
- All three offer a visual editor, multivariate testing, and a maturity and ecosystem ABTestly does not have yet. ABTestly is A/B testing, code-first, and young.
Where ABTestly is better
- Edge-native delivery. The test config is served from Cloudflare's edge in 300+ cities with no origin round-trip, and the variant applies on first paint behind a scoped anti-flicker hide.
- Code-first by default. Experiments are JSON: version-controlled, diffable, and reviewable, with raw JavaScript and CSS per variant. No editor state living outside your repo.
- Statistical transparency. The whole methodology — visitor dedupe, confidence-interval math, verdict thresholds, and SRM detection — is published. Nothing is called a winner below 95% confidence.
- Snippet footprint stated up front. A roughly 10KB gzipped runtime and a loader under 1.5KB, published so you can hold us to it.
- A permanent free plan rather than a time-limited trial, plus transparent published pricing from $79/mo and a 30-day money-back guarantee on paid plans.
Which should you pick?
Pick Optimizely if you need enterprise-grade experimentation, feature flags, the deepest stats engine, and a large integration stack, and the budget to match.
Pick VWO if you want one all-in-one tool with heatmaps, surveys, and a visual editor that marketers can drive without a developer.
Pick Convert if you want code access and transparent statistics from an established vendor with a wide integration catalogue.
Pick ABTestly if your experiments are built by people who write code, you want edge delivery and a JSON workflow in version control, you report into GA4, and you'd rather start on a free plan and see published statistics than sit through a sales call (our pricing).
Quick answers
Which A/B testing tool is best for developers?
It depends on what you optimise for. Optimizely has the deepest enterprise tooling and the most mature stats engine. Convert is the most transparent of the big three on statistics and the most code-friendly. VWO is the gentlest on-ramp and the broadest all-in-one. ABTestly is the most code-first and edge-native of the set: experiments are JSON in version control, delivered from Cloudflare's edge, with a fully published statistics methodology and a permanent free plan.
Which is best for single-page apps?
All four handle SPAs by different routes. Optimizely uses conditional activation plus waitForElement and waitUntil. VWO exposes a virtual page load API. Convert re-evaluates on history.pushState but leaves you to undo your own DOM changes. ABTestly has a per-site SPA mode that re-runs the lifecycle cleanup-first on route changes, so a variation does not leak across virtual pages.
What does ABTestly not do that the others do?
ABTestly has no visual editor (experiments are code and JSON), it does A/B testing rather than the full multivariate and feature-flag suites Optimizely and Convert offer, it has a single native GA4 integration rather than a large marketplace, sequential testing is on the roadmap rather than shipped, and it does not yet publish formal compliance certifications. If you need any of those today, one of the established tools is the safer pick.
What does ABTestly do that the others do not?
Edge delivery of the test config from 300+ Cloudflare locations with a roughly 10KB gzipped runtime, a code-first JSON workflow that lives in version control, a fully published statistics methodology (95% confidence interval on every lift, an SRM chi-square check, and no verdict declared below 95% confidence), and a permanent free plan rather than a time-limited trial.
Optimizely, VWO, and Convert are trademarks of their respective owners. ABTestly is not affiliated with or endorsed by any of them.
Questions about a switch? Book 20 minutes or email [email protected]. — The ABTestly team