The Best A/B Testing Tools in 2026 (Tested and Ranked)

PostHog

PostHog started as product analytics and grew into an all-in-one product platform. Experiments sit right next to your event data, session replays, and feature flags, which means you don't have to wire up a separate tool just to run a test. You define a flag, attach a goal metric you're already tracking, and PostHog handles the stats.

This is the tool I recommend to most startups. The reason is integration. When a test wins, you flip the same flag to 100% and ship. When it loses, you can drop into session replays and watch why people bounced, without leaving the app.

Best for: product-led startups and engineering teams who want experiments, analytics, and flags under one roof.

Pricing: experiments are billed together with feature flags, and the free tier covers 1 million flag requests per month plus 1 million analytics events. After that it's pure pay-as-you-go, starting at $0.0001 per flag request and dropping fast at volume. There's no monthly platform fee, and you can set billing caps so a traffic spike never produces a surprise invoice.

The catch: PostHog assumes you're comfortable with events and a bit of instrumentation. If you want a marketer to point at a button and change its color without touching code, this isn't the smoothest path. The visual experiment editor exists but it's clearly the second-class citizen next to the developer workflow.

Statsig

Statsig was built by ex-Facebook engineers who wanted to bring Meta-style experimentation to everyone else. It shows. The statistics are the real draw here: CUPED variance reduction, sequential testing, and Bonferroni corrections are all available, and unusually, they're on the free tier rather than locked behind an enterprise contract.

If you care about experiment velocity (running dozens of tests at once without your stats falling apart), this is the platform I'd pick. Companies like OpenAI and Notion run on it, which tells you it scales.

Best for: product teams that run experiments constantly and want trustworthy stats out of the box.

Pricing: the free Developer plan includes 2 million events per month, 100,000 session replays, unlimited flag checks, and unlimited seats. Pro starts at $150/month with 5 million events, and overages run $0.05 per 1,000 events. For a small team that's effectively free for a long time.

Where it falls short: Statsig is a product analytics and experimentation tool, not a marketing CRO suite. There's no slick visual editor for non-technical marketers, and the breadth of analytics can feel like a lot if all you wanted was a simple split test on a pricing page. The depth is the point, but it's also the friction.

GrowthBook

GrowthBook is the open-source option I keep recommending to teams that care about data ownership. The self-hosted edition is MIT-licensed and free with unlimited users, flags, and experiments. The clever part: instead of duplicating your data, GrowthBook queries your existing warehouse (BigQuery, Snowflake, Redshift, ClickHouse) to compute results. Your experiment data never leaves your infrastructure.

For privacy-conscious teams, or anyone allergic to per-user pricing, this is a strong fit. You pay for the people running tests, not for every visitor who sees one.

Best for: data teams with a warehouse who want full control and predictable costs.

Pricing: self-hosted is free forever. GrowthBook Cloud has a free Starter plan (up to 3 users, 1M events), and Pro is $40 per user per month, which adds advanced stats and the visual editor. Enterprise with SSO and audit logs is quote-based.

The catch: self-hosting means you own the ops. Someone has to deploy it, keep it running, and connect the warehouse. If your team can't spare that, the Cloud plan removes the headache but the per-seat math can climb once you add more than a few people. It's also less polished for pure marketers than VWO or Convert.

If you're still mapping out which tools belong in your stack, our roundup of the best AI agents and the broader top tools directory are worth a look alongside this one.

VWO

VWO is the visual-editor heavyweight that most marketers know. You can build a test by clicking on elements and editing them in place, no developer required, then target by audience and watch a clean reporting dashboard. After the merger with AB Tasty, it sits in the middle of the market: more approachable than Optimizely, more full-featured than the lightweight tools.

Best for: marketing teams that want a polished point-and-click experience and don't want to write code.

Pricing: VWO starts around $299/month and scales by traffic, with a limited free plan for low-traffic sites. The Growth, Pro, and Enterprise tiers add multivariate testing, advanced targeting, and faster support as you climb.

Where it falls short: the traffic-based pricing gets expensive fast if you have real volume, and the free plan is tight enough that most serious users outgrow it quickly. There's also some uncertainty about the product roadmap while the VWO and AB Tasty teams integrate. I'd want to see how the combined company prices things once the dust settles.

Optimizely

Optimizely is the enterprise gold standard and prices like it. This is the platform you choose when you have a dedicated experimentation team, run thousands of tests a year, and need features like multi-arm bandits and the stats accelerator that dynamically shifts traffic to winning variations. It's trusted by over 9,000 companies including the kind of brands with their own optimization departments.

Best for: large organizations with real budget and a team whose full-time job is experimentation.

Pricing: gated and custom. Industry estimates put entry-level deals around $50,000+ per year, and large contracts run well past $100K. You won't find a number on the site.

The catch: it's overkill for almost everyone reading this. The power is real, but so is the cost and the implementation overhead. If you're a startup or a lean marketing team, you'll pay enterprise prices for capacity you'll never touch. Pick this when you've genuinely outgrown everything cheaper, not before.

Convert

Convert (Convert Experiences) is the affordable, privacy-first pick in the marketer-friendly tier. It does clean visual A/B testing with strong GDPR and consent handling, which is why a lot of agencies and EU-based teams favor it. It hits a sweet spot between VWO's polish and a budget you can actually defend.

Best for: agencies and privacy-conscious teams who want a visual editor without enterprise pricing.

Pricing: the Growth plan is $299/month for 100,000 tested users (monthly billing), and Pro is $499/month for 250,000 users on annual billing. Each additional 100K tested users adds $299/month. Enterprise is custom.

Where it falls short: it's still a flicker-prone client-side testing tool at heart, like most visual editors, and the tested-user pricing means a high-traffic site can rack up real costs. It also lacks the deep product-analytics layer you get from PostHog or Statsig, so it's a CRO tool more than an experimentation platform.

Unbounce

Unbounce isn't a general A/B testing tool, it's a landing page builder with testing built in, and that focus is exactly why it's here. If your experiments are mostly about landing pages for paid campaigns, Unbounce lets you build variants and test them without touching your main site. Its Smart Traffic AI automatically routes each visitor to the variant most likely to convert them, which the company claims lifts conversions roughly 30% over a plain 50/50 split.

Best for: paid-acquisition teams running landing page tests at speed.

Pricing: plans start at $99/month (Build), with classic A/B testing on the Experiment plan at $149/month, and Smart Traffic on Optimize at $249/month. Annual billing knocks 25% off, and there's a 14-day trial.

The catch: it only tests pages you build inside Unbounce. You can't run an experiment on your existing app or product. And Smart Traffic, the headline feature, is gated to the $249 tier, so the cheaper plans are just standard split testing.