Email A/B Testing Tools: 14 Platforms Compared for 2026

For a marketing team that wants to compare subject lines or content blocks in regular campaigns, Brevo is the best starting point among the 14 platforms in this guide. Its Standard plan is listed at $18 a month, starts at 5,000 emails a month, and its plan description includes automation, A/B testing and advanced reports. That combination of a named testing feature, a published entry price and a broad email-and-SMS toolset is why it leads the shortlist. It is a starting point rather than a verdict. The right tool depends on whether your test measures a single send, a branch inside a sequence, a product event, or the growth of a publication.

This guide compares the platforms by the testing job they are best suited to, the list-size pricing that applies to that job, and the limitations that tend to show up after the first pilot. Feature names, limits and prices change. Read the official pricing page of each vendor on the day you decide, and treat the figures below as a dated snapshot.

What “email A/B testing” means in practice

The phrase covers three different jobs, and most buying mistakes come from mixing them up. The first job is campaign testing: you send two versions of one message to split segments of an audience and compare results. Subject lines, preheaders, hero images, offers and send windows are typical variables. Campaign tests are fast to set up and easy to read, but they usually end at the first click or open. They rarely tell you whether the winning version produced a paying customer or a retained subscriber.

The second job is automation testing. Here the variants sit inside a welcome series, an onboarding track, an abandoned-cart flow or a nurture sequence. The question is not which email got more clicks on Tuesday, but which path moves a contact toward a defined next step over several days. This requires branching logic, exit rules and a way to suppress people who have already converted. Not every campaign-focused tool supports this well.

The third job is product experimentation. A product team randomizes users into arms, sends a message to each arm, records product events and exports results to an analytics system. The email tool is one component. Assignment must persist across sessions and devices, event names must be stable, and the team needs someone who can read a confidence interval. Several vendors in this guide are built for that style of work; others are deliberately simpler.

A feature checklist alone will mislead you. A campaign composer with a split-test button does not provide holdout groups, and an event-driven journey tool does not necessarily give a non-technical marketer a clean way to compare two newsletter headlines. Decide which job matters most for the next six months, then judge each platform against that job.

Pick the outcome before you pick the tool

Open rate is a weak primary metric for most commercial tests. Mailbox providers and privacy features can change how opens are recorded, so a difference in opens may reflect display behavior as much as reader interest. For a more reliable decision, define one downstream outcome before the test starts. Depending on the business, that might be a click to a pricing page, a trial activation, a purchase, a reply from a prospect, a booked call, or a subscriber still active thirty days later.

Keep guardrail metrics visible while the test runs. Unsubscribes, spam complaints, bounces, and revenue per recipient show whether a variant is winning by annoying people or by attracting the right ones. If a subject line raises clicks but doubles complaints, it has not won. Before you interpret a sudden change in performance, read the deliverability guide, because a shift in inbox placement can look like a test result when it is really a sending problem.

How the information in this guide was gathered

Pricing and plan details come from each vendor’s public pricing page as read on October 7, 2026. Feature statements are limited to what those pages and the vendor’s own plan descriptions say. The guide does not report hands-on trials, benchmark results or performance numbers, and it does not rank the platforms by score. The “best for” labels describe where each tool’s stated scope fits a job; they are not a claim that the tool is superior for everyone.

Prices are list prices for the band or plan named. Taxes, overages, SMS or other add-ons, implementation fees and onboarding charges are excluded unless a row says otherwise. Where a vendor price depends on a contact count, sending volume or seat count that this guide did not list for your size, the table says so instead of estimating.

Shortlist at a glance

The table below summarizes the 14 platforms by the testing job they fit, the entry price named on the vendor page, and the limitation most likely to matter after purchase. Use it as a filter, then read the detailed section for any tool that stays on your list.

Tool	Best for	Testing scope on vendor pages	Entry price (plan, billing)	Main limitation
Brevo	Small teams mixing email and SMS	A/B testing listed on Standard	Starter $9/mo and Standard $18/mo, both starting at 5,000 emails a month, monthly billing	Priced by monthly send volume; confirm what counts as a send
Mailchimp	Generalist campaign teams	Campaign comparisons; test types depend on plan	Free to 250 contacts and 500 sends a month; Standard $20/mo at the 500-contact selector, monthly billing	Contact tiers raise cost quickly; confirm which test types your plan includes
Klaviyo	Ecommerce flows	Catalog and event data drive flows; test controls depend on plan	Free: 250 profiles and 500 sends a month; 1,000 profiles at $30/mo, monthly billing	Profile growth drives cost; SMS is priced separately
Omnisend	Small ecommerce lists using email and SMS	Ecommerce automation; confirm test options on your plan	Free: 250 contacts and 500 emails a month; Standard $11.20/mo at 500 contacts, shown with a first-three-month promotional rate	The promotional rate is time-limited; SMS pricing varies by country and volume
ActiveCampaign	Sales nurture and branching automation	Automation and CRM-linked sequences; split-test scope to confirm	Starter $15/mo at 1,000 contacts, monthly or annual billing	Costs rise with contact count; advanced segmentation needs Pro
Customer.io	Product-event and lifecycle messaging	Event-triggered workflows; experiment design is yours to build	Essentials from $100/mo; 10,000 profiles at $145/mo, monthly billing	Needs disciplined event naming and identity rules; Premium is custom-priced
HubSpot Marketing Hub	CRM-connected marketing teams	Campaign tools with CRM context; tiers differ by hub	Free Marketing Hub tools; Starter $7/mo, Professional $800/mo, Enterprise $3,600/mo; per-seat model	Step-up cost to Professional is large; seat count changes the total
MailerLite	Simple newsletters and small editorial programs	Campaign iteration; automation depth depends on tier	Free up to 250 subscribers and 2,500 emails a month; Comfort $12/mo monthly or $10.80/mo billed annually, 500-subscriber tier	Confirm which automation features the Comfort plan includes
Campaign Monitor	Design-led teams and agencies	Reviewable campaign variants; test scope to confirm	Lite $13/mo monthly or $11.70/mo annual, 500-contact band	Premier adds support features at a much higher price
GetResponse	Course, webinar and funnel businesses	Campaign and automation comparisons; confirm scope	Starter $19/mo monthly or $15.58/mo annual; free trial, no ongoing free plan	The plan description does not list subscriber bands, so price your actual list
beehiiv	Publication growth loops	Newsletter and growth features; test controls to confirm	Free up to 2,500 subscribers; Lite $49/mo up to 100,000 subscribers	Subscriber-tiered pricing; yearly billing saves up to 20%
Kit	Creator-led newsletters	A/B test subject lines listed on Creator	Free up to 10,000 subscribers; Creator $33/mo billed yearly	Visual automations and sequences require Creator
Loops	Modern SaaS lifecycle messaging	Experiment controls not described on the pricing page	Free: up to 4,000 sends per rolling 30 days to the 1,000 newest contacts; Growing Audience $99/mo	The free plan carries a sending limit and a footer
Resend	Developer-owned email	No campaign A/B feature listed; you build assignment and analysis	Free 3,000 emails a month; Pro marketing $40/mo at 5,000 contacts	Requires engineering work for experiments and reporting

Brevo: best starting point for campaign subject-line tests

Brevo is the most direct answer for a team whose question is “which subject line or content block wins on this newsletter?” The Standard plan is listed at $18 a month on monthly billing, and the plan description includes automation, A/B testing and advanced reports. It also starts at 5,000 emails a month, which means the price should be read against your real send volume rather than your contact count alone.

Its strength is breadth. A marketing team can run campaigns, transactional messages and SMS from one account, which suits small organizations that do not want separate tools for each channel. The weakness is the same breadth. A wide messaging suite does not automatically provide deep experimentation. Before you commit, confirm exactly which A/B variables the Standard plan allows, how winners are chosen, and whether a winning variant can be sent automatically to the rest of the list.

Brevo also publishes a free plan of 300 email sends a day for up to 100,000 contacts. That is useful for building a template library and testing deliverability, but the free plan’s description does not list A/B testing, so do not assume a split test is available there. Pricing details are on Brevo’s pricing page.

Mailchimp: familiar campaign workflow for generalist teams

Mailchimp suits teams that send regular campaigns and want a familiar production process without building an experimentation system. Its free plan covers up to 250 contacts and 500 sends a month, with a 250-per-day maximum. The Standard plan is listed at $20 a month for the default 500-contact selector, with up to 6,000 emails a month at that level. Larger contact bands raise the price: the 2,501–5,000 band is listed at $100 a month for up to 60,000 emails, and the 5,001–10,000 band at $135 a month for up to 120,000 emails.

The practical limitation is cost growth. A list that moves from a few hundred contacts into the low thousands can change the monthly bill substantially, so a subject-line test should be paired with a clear view of the list’s growth trajectory. Confirm which test types, winner rules and reports your plan includes before you build a process around them. Also check whether the plan you need has the send allowance for the test’s total audience, not just the portion receiving each variant. The Mailchimp pricing page sets out the contact bands in full.

Klaviyo: ecommerce flows that depend on catalog and purchase data

Klaviyo is a strong candidate when the experiment depends on browsing, cart, purchase, product or replenishment context. A meaningful ecommerce test might compare an offer, a product framing, or the timing of a flow step while suppressing recent buyers. Its value rises when the underlying data is clean, because the message can respond to what a shopper actually did.

Pricing follows profiles. The free plan covers 250 profiles and 500 sends a month. The email plan is listed at $30 a month for 1,000 profiles, $100 a month for 5,000, $150 a month for 10,000 and $400 a month for 25,000, all on monthly billing as shown on the pricing page. SMS is priced separately, so a team that adds text messages should model both channels. The main limitation is that profile growth, not message volume, usually drives the bill. If your list is growing quickly, model the next two bands before you begin the test.

For a revenue test, plan a holdout or a matched comparison from the start. Measure margin, repeat purchase and unsubscribes alongside clicks. A variant that wins on clicks can still reduce revenue per recipient. See Klaviyo’s pricing page for the current profile bands.

Omnisend: small ecommerce lists that also send SMS

Omnisend is designed for online stores that run email and SMS together and want automation templates built for ecommerce. Its free plan covers 250 contacts, 500 emails and 500 web push notifications a month. The Standard plan is listed at $11.20 a month for 500 contacts and 6,000 emails a month, but the figure shown on the pricing page is a promotional rate for the first three months, so the ongoing price should be confirmed before you budget. The Pro plan is listed at $41.30 a month for 2,500 contacts, with unlimited monthly emails and SMS starting at $0.007 per message.

The limitation is that SMS costs vary by country and volume, so a store that sells internationally cannot read the headline price as its real cost. Test design is also constrained by the list size: a small store may find that a two-variant test on a welcome flow reaches too few people to read in a reasonable time. For small lists, a directional result is often the most you can responsibly claim. Review the Omnisend pricing page for current SMS rates.

ActiveCampaign: branching sequences for sales and nurture

ActiveCampaign fits teams whose experiment lives inside a nurture or sales follow-up sequence. The useful question is whether a variant can be judged against a later business event, such as a qualified reply, a meeting booked, a trial action or a purchase, rather than against an early engagement signal alone. That requires a sequence that can branch and an outcome that the CRM records consistently.

Pricing starts at $15 a month for the Starter plan at 1,000 contacts, $49 a month for Plus, $79 a month for Pro and $145 a month for Enterprise, all listed at 1,000 contacts as the starting point. Prices scale with the contact count, so the list you are actually mailing determines the cost. The Starter description includes email marketing, marketing automation, standard CRM and ecommerce integrations, while Plus adds standard segmentation and landing pages and Pro adds advanced segmentation. If your test depends on advanced segmentation, the Plus plan may not be enough on its own.

Run a two-branch sequence with explicit entry rules, exit rules and sales suppression. Otherwise a contact who books a call can keep receiving nurture emails, which damages the test and the relationship at once. ActiveCampaign lists a free trial; confirm its length and what it includes on the ActiveCampaign pricing page.

Customer.io: event-driven experiments for product teams

Customer.io is relevant when the experiment is driven by product events, account attributes or lifecycle state. It can answer questions such as whether a different activation prompt changes a verified product action, provided the event names, identity rules and exclusions are stable. Its strength is flexible audience logic and a direct connection between a message and what a user did in the product.

The Essentials plan is listed at $100 a month, with a visual workflow builder and basic data integrations. Profile-based pricing is listed at $145 a month for 10,000 profiles, $235 for 20,000, $325 for 30,000, $415 for 40,000 and $505 for 50,000 or more, all on monthly billing. The listed bands do not show every profile count, so a list of 25,000 should be priced by asking the vendor directly. Premium uses custom profile volume and pricing. The Startup Program offers 12 months free to eligible early-stage companies that have raised under $10 million, according to the pricing page.

The main limitation is operational. Customer.io needs an owner for event definitions, identity resolution and analytics interpretation. Usage pricing can also be harder to forecast than a simple newsletter plan, so model profile growth and event volume before you sign. Pilot one activation path, document event freshness and exclusions, and have engineering validate the event payload before anyone trusts the result. The Customer.io pricing page lists the current bands.

HubSpot Marketing Hub: campaign tests with CRM context

HubSpot suits organizations where email results must be read alongside lifecycle stage, owner, deal or service history. It is valuable when marketing and sales need one governed place to define the audience and the downstream outcome. A campaign test tied to a CRM result is easier to defend in a planning meeting than a click count pulled from a separate tool.

Pricing is organized by hub and seat. The free Marketing Hub tools are listed as available, while the paid tiers are listed at $7 a month for Starter, $800 a month for Professional and $3,600 a month for Enterprise, with the pricing model described as per-seat. Because seat count changes the total, the monthly figure is a starting point rather than a team cost. The jump from Starter to Professional is large, so teams that only need email testing should ask whether the CRM context justifies it.

Agree on sales exclusions and attribution rules before any send. Otherwise a campaign test can be credited to the wrong team or can reach prospects a salesperson is already working. Current plan requirements are on HubSpot’s Marketing Hub pricing page.

MailerLite: simple newsletter iteration on a small team

MailerLite is a practical option when the test is simple, the list is permissioned and one small team builds and reviews the campaign. It keeps the learning loop short for subject lines, content framing or calls to action in a regular newsletter. Its free plan covers up to 250 subscribers and 2,500 emails a month.

The Comfort plan is listed at $12 a month on monthly billing or $10.80 a month billed annually, based on the 500-subscriber starting tier. The Power plan is listed at $25 a month or $22.50 a month billed annually for the same starting tier, with unlimited monthly emails. The Comfort monthly email allowance is listed as 10 times the subscriber-tier ceiling. Those details matter for a test, because a variant that is sent to a large share of a small allowance can leave little room for the rest of the calendar.

Before you use MailerLite for behavioral experimentation, confirm which automation features, reports and integrations your plan includes. Pilot one complete signup-to-conversion path and record the manual work it takes, not only the winning metric. Pricing is on the MailerLite pricing page.

Campaign Monitor: reviewable campaign work for agencies

Campaign Monitor fits design-led teams and agencies that need a repeatable approval process around campaign variants. The most useful tests are controlled production questions, such as content hierarchy, subject line or call-to-action placement, rather than highly instrumented product experiments. The approval workflow matters more here than an event engine.

The Lite plan is listed at $13 a month on monthly billing or $11.70 a month billed annually, based on a 500-contact band and five times the subscriber emails per month. Essentials is listed at $31 a month or $27.90 billed annually with unlimited email sends, also at the 500-contact band. Premier is listed at $171 a month or $153.90 billed annually and adds premier support, including phone support. A 30-day free trial is listed with 500 contacts and a 500-email limit.

The limitation is that complex lifecycle logic may need another system. Verify automation depth, segmentation, experiment reporting, integrations and subscriber economics against your own list before signing an agency contract. A useful pilot is one approved campaign taken from brief to report, with every manual handoff counted. The Campaign Monitor pricing page shows the bands.

GetResponse: funnels, webinars and courses

GetResponse is a candidate for teams that combine email campaigns with landing pages, webinars or funnel-style automation. Its testing value depends on whether the business can connect a variant to registration, attendance, purchase or another outcome rather than stopping at opens. For a course seller, the outcome that matters is often the enrollment or the completed module, not the click.

The Starter plan is listed at $19 a month on monthly billing or $15.58 a month billed annually, with unlimited monthly email sends, a welcome series, one automation workflow, landing pages and signup forms. Marketer is listed at $59 a month or $48.38 billed annually and adds unlimited workflows, advanced segmentation, abandoned-cart recovery and sales funnels. Creator is listed at $69 a month or $56.58 billed annually and adds webinars, a website builder, a course creator and premium newsletter subscriptions. GetResponse offers a free trial on paid plans and does not list an ongoing free plan.

The pricing page does not show every subscriber band, so the cost for your list must be confirmed directly. Also compare total operator time against your current stack, because a funnel tool with many components can add setup work that a campaign-only tool does not. The GetResponse pricing page has the current plan details.

beehiiv: publication growth and subscription loops

beehiiv belongs on a publication shortlist when the experiment concerns newsletter growth, referral behavior, paid subscriptions or issue-level engagement. The product question is often editorial and acquisition-oriented rather than transactional or lifecycle-oriented. An issue headline, a referral prompt or a paid-subscription offer are all plausible tests.

The Free plan covers up to 2,500 subscribers and unlimited email sends, with one publication. The Lite plan is listed at $49 a month for up to 100,000 subscribers, and Pro at $95 a month for up to 250,000 subscribers, with advanced analytics and priority support. Subscriber-tier pricing applies, so the cost for a 5,000-subscriber list is listed separately at $109 a month on monthly billing or $95 a month billed yearly for Lite, and $139 a month or $119 a month billed yearly at 10,000 subscribers. Yearly billing is described as saving up to 20 percent.

Pilot one recurring issue with one growth action, and compare qualified subscriber growth with the publication’s baseline. Watch unsubscribe and complaint rates at the same time. Review the beehiiv pricing page for the full set of plan limits.

Kit: creator-led tests on a free-to-start list

Kit is a natural fit when the newsletter, the creator’s voice and the product recommendation form the core of the audience relationship. Testing can focus on editorial framing, lead-magnet follow-up or a clear offer transition while keeping the creator’s cadence. The free plan covers up to 10,000 subscribers with unlimited landing pages and forms, unlimited email broadcasts and audience tagging and segmentation.

The Creator plan is listed at $33 a month billed yearly and adds unlimited visual automations, unlimited email sequences, A/B test subject lines and removal of Kit branding. The Pro plan is listed at $66 a month billed yearly and adds Subscriber Signals, unlimited users, deliverability reporting and a newsletter referral system. Paid plans carry a 14-day free trial that does not require a credit card.

The limitation is that Kit is not a substitute for product-event or complex CRM experimentation. If you need a test that depends on what users do inside an application, a tool built for event data will fit better. For a creator, the most useful pilot is a welcome or launch sequence measured on qualified clicks, replies and unsubscribes. Details are on the Kit pricing page.

Loops: lifecycle messages for SaaS teams

Loops is worth considering for SaaS teams that want lifecycle messages close to product events in a focused tool. Its best test is one where the event contract is simple enough to audit, such as signup, activation, a trial milestone or a cancellation signal. A narrow event contract also makes it easier to explain a result to a non-technical colleague.

The Early Stage plan is listed at $0 and allows up to 4,000 sends in any rolling 30 days to the 1,000 newest contacts, with all features included, a Loops footer and a rate of 10 emails per second. The Growing Audience plan is listed at $99 a month and covers unlimited sends to subscribers, transactional sends to users outside the audience and all features. The pricing page does not describe the experiment controls, so ask for a written list of what the plan includes before you make it the system of record. The Loops pricing page is the place to confirm plan scope.

Pilot a single onboarding path with an engineering-reviewed event map and a defined stop condition for users who have already activated.

Resend: developer-owned experiments

Resend is primarily an email delivery and developer workflow choice, not a turnkey campaign experimentation suite. It can still be the right foundation when a product team wants version control, API-level control and an analytics layer it owns. The free plan lists 3,000 emails a month, and the marketing plans are listed at $40 a month for 5,000 contacts, $80 a month for 10,000 contacts and $180 a month for 25,000 contacts on the pricing page, with a free tier at 1,000 contacts that includes unlimited broadcast sending.

The team must supply randomization, assignment that persists across retries and devices, reporting, consent logic and the statistical analysis. Do not buy it expecting a visual test builder. A useful pilot is a small, non-critical lifecycle message, with a written rule for how a user stays in the same arm. Pricing details are on the Resend pricing page.

How to choose by intent

Start from the question rather than the vendor name. The table below pairs common testing questions with the shortlist that fits them and the starting price to confirm. Prices are the monthly figures listed on each vendor’s pricing page for the band named.

If your question is…	Start with…	Why	Starting price to confirm
Which subject line wins on a newsletter?	Brevo Standard or Kit Creator	Both list A/B testing on the plan named	Brevo $18/mo monthly; Kit $33/mo billed yearly
Which branch in a nurture sequence creates pipeline?	ActiveCampaign Starter or Plus, or HubSpot Marketing Hub	Automation with CRM context; outcome can be read in the sales record	ActiveCampaign $15/mo at 1,000 contacts; HubSpot Starter $7/mo per seat
Which message changes a product activation?	Customer.io or Loops	Event-triggered messages that respond to in-product behavior	Customer.io $145/mo at 10,000 profiles; Loops $99/mo Growing Audience
Which offer lifts ecommerce revenue?	Klaviyo or Omnisend	Purchase, catalog and SMS data support revenue-focused flows	Klaviyo $30/mo at 1,000 profiles; Omnisend Standard $11.20/mo at 500 contacts, promotional rate
Can engineering own the whole experiment?	Resend	API-first delivery; assignment and analysis are built in your code	Pro marketing $40/mo at 5,000 contacts
Which issue or referral prompt grows a publication?	beehiiv	Publication growth, referral and subscription features	Lite $49/mo up to 100,000 subscribers

What the list-size bands mean for your budget

Most email tools price by contacts, profiles, subscribers or sends, and a small change in list size can move a plan into a more expensive band. The table below shows the figures that vendor pages list at three common list sizes. Where a band is not listed for a given size, the cell says so rather than estimating a price. Figures exclude tax, SMS, overages and add-ons.

Tool	About 1,000 contacts	About 5,000 contacts	About 10,000 contacts
Brevo	Free plan: 300 sends a day, up to 100,000 contacts	Starter $9/mo or Standard $18/mo, both starting at 5,000 emails a month	Priced by monthly email volume; confirm the band for your sends
Mailchimp	Not listed at 1,000; Standard $20/mo at the 500-contact selector	$100/mo for the 2,501–5,000 band, up to 60,000 emails a month	$135/mo for the 5,001–10,000 band, up to 120,000 emails a month
Klaviyo	$30/mo, email plan at 1,000 profiles	$100/mo, email plan at 5,000 profiles	$150/mo, email plan at 10,000 profiles
ActiveCampaign	Starter $15/mo, Plus $49/mo, Pro $79/mo, all starting at 1,000 contacts	Not listed at this size; price by asking the vendor	Not listed at this size; price by asking the vendor
Customer.io	Essentials from $100/mo; profile band not listed at this size	Not listed exactly; the 10,000-profile band is $145/mo	Essentials 10k profiles $145/mo, billed monthly
MailerLite	Comfort $12/mo at the 500-subscriber tier; 1,000 not listed	Not listed at this size	Not listed at this size
Campaign Monitor	Lite $13/mo or Essentials $31/mo at the 500-contact band; 1,000 not listed	Not listed at this size	Not listed at this size
GetResponse	Starter $19/mo monthly; subscriber bands not listed	Not listed at this size	Not listed at this size
beehiiv	Free plan up to 2,500 subscribers	Lite at 5,000 subscribers: $109/mo monthly or $95/mo billed yearly	Lite at 10,000 subscribers: $139/mo monthly or $119/mo billed yearly
Kit	Free plan up to 10,000 subscribers; automations need Creator at $33/mo billed yearly	Free plan up to 10,000 subscribers	Free plan up to 10,000 subscribers
Loops	Early Stage free plan with 4,000 sends per rolling 30 days to the 1,000 newest contacts	Growing Audience $99/mo; contact band not listed	Growing Audience $99/mo; contact band not listed
Omnisend	Not listed at 1,000; Standard $11.20/mo at 500 contacts, Pro $41.30/mo at 2,500	Not listed at this size	Not listed at this size
Resend	Marketing free tier at 1,000 contacts, with unlimited broadcast sending	Pro marketing $40/mo at 5,000 contacts	Pro marketing $80/mo at 10,000 contacts

HubSpot Marketing Hub is seat-based rather than contact-based, so it is not in the table. Its Starter, Professional and Enterprise figures in the shortlist depend on how many seats you buy. Ask for a seat-level quote before comparing it to a contact-based tool.

Be careful with the arithmetic when you compare a free plan with a paid one. A free plan that allows 10,000 subscribers can still be a poor fit if it lacks the automation or A/B feature you need. Conversely, a paid plan that looks expensive at 1,000 contacts may be the only option that includes the test type your team requires. The cheapest plan is the one that supports the test you need at your real volume.

Setup and pilot checklist

The checklist below turns a shortlist into a pilot. It is written for a campaign or lifecycle test, but the same steps apply to a product experiment with a longer timeline.

Step	Action	Done when
1. State the question	Write one sentence, such as “Does the revised welcome email raise pricing-page visits within seven days?”	One owner has signed the sentence
2. Pull list and volume data	Export contact counts, send volume and bounce rates from your current tool for the last twelve months	A file shows the band each candidate would fall into
3. Shortlist three tools	Read each vendor’s pricing page on the day you decide and save a dated copy	Three dated pricing records sit in the decision file
4. Confirm test controls in writing	Ask pre-sales how variants are split, how winners are chosen, whether a holdout is possible and whether winners send automatically	Written answers are received for each candidate
5. Test the import	Import a sample of about 500 contacts with consent fields, and check the counts	Imported counts match the export, and suppressed contacts are absent
6. Set suppression rules	Exclude recent purchasers, complainers, unsubscribes and sales-owned leads from the test	The exclusion list is signed off by sales or support
7. Freeze the metric	Record the primary outcome, guardrails and test window before the first send	The plan is saved with a date
8. Run and record	Send the test, watch guardrails, and avoid stopping early on a single attractive number	Sample counts, delivery signals and the next action are logged
9. Decide and keep the export	Choose the tool, cancel any trial you do not need, and export your contact data	The export file is stored and readable

Running the pilot without fooling yourself

Start with one audience, one hypothesis, two variants and one primary outcome. Decide the allocation, the test window, the exclusion rules, the minimum effect worth acting on and the guardrails before the first send. A test that changes its metric after the results arrive will produce an answer that nobody can defend.

If the audience is small, call the result directional rather than conclusive. There is no universal rule such as “1,000 subscribers per variant” that holds for every baseline, effect size, conversion rate and decision. Use a sample-size calculator with your baseline and the smallest change you would act on, and report the uncertainty range where your tool provides one. A difference of a few clicks in a small list is usually noise.

Run the test long enough to cover the normal behavior window for the outcome. A purchase that typically happens three days after a click needs more than a single day of observation. Avoid checking the dashboard repeatedly and stopping at the first favorable number. If you need an interim look, decide in advance how many looks you will allow and what you will do with each.

After the test, write down the sample counts, the assignment integrity (whether people stayed in their arm), the delivery and complaint signals, the uncertainty range and the next action. Keep that record with the pricing snapshot and the export file. The next person who evaluates the same tool will need it. For segmentation design that feeds a test, see the segmentation guide, and for a wider platform selection process, see the SaaS buying guide.

Common mistakes when comparing A/B testing tools

The first mistake is comparing feature names instead of test controls. “A/B testing” on a pricing page can mean split subject lines, split content, split send times or split automation branches. Ask which variables the tool supports and whether a variant can be held back for a true control group. A split that only changes the subject line cannot tell you whether the offer itself worked.

The second mistake is ignoring the cost of growth. A plan that fits a list of 1,000 contacts may not fit the same list two years later, and a plan priced by sends can become expensive when a test sends the same message to several segments. Model your list at two or three sizes and include the add-ons you will need, such as SMS.

The third mistake is treating the winner as a permanent rule. A subject line that wins this month may fail next quarter because the audience has changed. Keep a log of tests, and retest important findings before you build a standing process around them. The fourth mistake is letting the tool define the question. Start from the decision, then choose the platform that supports it.

Buying and contract caveats

Compare total operating cost rather than the headline monthly fee. Include contacts or profiles, sends, seats, SMS or other channels, event volume, data services, overages, migration, implementation and the time your analyst will spend interpreting results. Ask each vendor whether assignment, historical data, exports and reporting are included at the plan you would actually buy.

Before you sign, request a walkthrough using your real event names and one representative journey. Confirm how winners are selected, how ties and missing conversions are handled, whether users stay in a consistent variant, and which features are in the plan versus available only as add-ons. Keep the dated pricing records and the written answers from pre-sales in your decision file. Pricing pages change, and a memo built on a dated record is easier to defend than one that relies on memory.

Bottom line

Choose the smallest platform that can keep a test assignment consistent, connect the message to a meaningful outcome, and show enough evidence for a responsible decision. Brevo Standard is the most direct fit for campaign subject-line tests at a published $18 a month. Klaviyo suits catalog-led commerce at a published $30 a month for 1,000 profiles. Customer.io and Loops fit event-led SaaS, and Resend fits teams that will build the experiment themselves. The pilot should decide the fit, not a feature matrix or a vendor’s claimed uplift.

Frequently asked questions

Which tool should I pick if I only need subject-line tests?

For a campaign-only newsletter, Brevo Standard is the most direct starting point because its plan description lists A/B testing alongside automation and advanced reports, at $18 a month on monthly billing. Kit is the alternative if your newsletter is creator-led, since its Creator plan lists A/B test subject lines at $33 a month billed yearly. Confirm which variables each plan supports before you commit.

Do free plans include A/B testing?

The free plans described in this guide do not list A/B testing in their feature descriptions. Kit’s free plan covers broadcasts, landing pages and tagging, while subject-line tests are listed on Creator. Brevo’s free plan lists a daily send limit and contact storage. If a free plan is your only budget, check its feature list in writing before you design a test around it.

How many subscribers do I need per variant?

There is no universal threshold. The sample you need depends on your baseline rate, the smallest difference you would act on and the outcome you measure. Use a sample-size calculator with those inputs, and treat any result from a small list as directional. A difference that looks large in a tiny audience can disappear with more data.

Are open rates still a reliable primary metric?

Open rates are a weak primary metric for most commercial tests because mailbox providers and privacy features can change how opens are recorded. A more reliable choice is a downstream action such as a qualified click, a trial activation, a purchase or a reply. Keep unsubscribes, complaints and bounces visible as guardrails so that a winning variant does not hide a problem.

Why do prices on this page differ from what I see later?

The prices here are read from each vendor’s public pricing page on October 7, 2026, and they reflect the bands and billing terms named on that page. Vendors change packaging and promotional offers. If the vendor’s page differs from this guide, the vendor’s page governs, and you should save a dated copy before signing.

Can I move my list from one tool to another?

Yes, but only the consented, active portion should move. Export contacts with their consent fields, suppression lists and tags. Import a small sample first and check the counts. Carry over unsubscribes and complaint suppressions so that you do not email people who have already opted out. Rebuild automations in the new tool rather than assuming an export will preserve them.

Which tools offer a free trial?

Kit lists a 14-day free trial on paid plans with no credit card required. Campaign Monitor lists a 30-day free trial with 500 contacts and a 500-email limit. GetResponse offers a free trial on paid plans. ActiveCampaign lists a free trial without stating its length on the pricing page, so confirm the duration and included features before you start.

Should a developer team build its own A/B testing?

Sometimes. Resend and similar API-first services give engineers control over delivery, templates and logs, but they do not provide a finished experiment engine. If you build your own assignment, you must also store the assignment so users stay in the same arm across retries and devices, define the event schema, and do the analysis. For many teams, a lifecycle tool with built-in event triggers is less work than building the full stack.