What is the best customer retention software for ecommerce?

There is no single best one. Compare two things: who starts the work, and how the result is measured. Klaviyo and Omnisend suit a store with someone who will build and maintain flows. Shopify's own tools suit one marketer. A retention tool such as Tranthor suits a store where nobody owns the second order. Manual retention suits an owner still learning which moments deserve a campaign.

Does AI retention software send messages on its own?

It depends on the tool and the setting. Klaviyo's help page says Composer does not send or publish marketing content on its own, and Flows AI produces a draft that you set to Live yourself. In Tranthor the first run of every playbook is drafted for your approval, auto-send is off by default, and you switch it on per playbook after one approved run.

How do Klaviyo and Omnisend count revenue from a campaign?

Both credit sales to messages under a rule. Klaviyo says it uses last-touch attribution, with new-account defaults of five days for email clicks, email opens and text clicks. Omnisend credits a sale only if the customer engaged with the message, with defaults of seven days for email and 24 hours for SMS. Both let you adjust the windows.

Does attributed revenue prove retention software works?

No. Attributed revenue is credit under a rule, not proof of cause. The test is to hold back a random group of eligible customers, send to the rest, and compare repeat orders over the same window. Tranthor shows lift only for campaigns where you set up a holdout, and only once both groups reach 100 customers.

Can a small store run a holdout test?

Yes, by hand. Klaviyo's global holdout groups need at least 400,000 total profiles, but you can hold back a random share of an eligible audience yourself and compare repeat orders. Use enough customers in each group that the difference means something. Tranthor's floor of 100 per group is a minimum for showing a number, not a guarantee that the difference is real.

Should retention software send automatically from day one?

No. Start in review so you can inspect who is eligible and what each message says. Allow automatic sending only for a play whose behaviour you understand, and within limits you approve.

Best Customer Retention Software for Ecommerce (2026)

Customer retention software for ecommerce is any tool that helps an online store bring buyers back for another order. Almost every tool can send a message. They differ on two harder questions: who starts the work, and how the result is measured. This guide compares the options on those two.

We make Tranthor, which is one of the options below, so read our description of it as a vendor's. Facts about other products come from their own pages, read in October 2026 and linked at the end. This is grouped by situation and is not a ranking.

Quick Answer

Pick by who will start the work and how you will judge it. If someone will build and maintain flows, Klaviyo and Omnisend are established choices, and both now include AI help with drafting. If one marketer runs a few flows, Shopify's own tools may be enough. If nobody owns the second order, look at a retention tool that finds the moment and drafts the campaign, such as Tranthor. Whatever you choose, do not accept attributed revenue as proof. Hold back a group of customers and compare. For a Shopify-specific view, see best CRM for Shopify stores.

What retention software has to do
Who starts the work
How each tool credits revenue
Retention software by situation
Where Tranthor fits
A 30-day pilot
FAQ

What Retention Software Has to Do

Four jobs sit inside retention, and most tools cover only some of them.

Spot. Decide which customer moment is worth acting on, such as a second purchase, a reorder or a lapse.
Prepare. Build the audience, write the message and choose the channel and timing.
Send. Deliver it, on the right channel, to people who may receive it.
Prove. Show whether the campaign caused repeat orders, not only whether it was opened.

Sending is the part every tool does well. The other three are where the work, and the difference between tools, sits. For the stage-by-stage view of which moments matter, see customer lifecycle management software for ecommerce.

Who Starts the Work

AI drafting is now common, so a review step is no longer a differentiator. The useful question is what triggers the draft: a prompt you write, a recommendation the tool makes, or a moment found in your store data.

Tool	What it drafts	What starts it	What waits for you
Klaviyo Composer	Email, SMS and push campaigns, flows and segments, per its help page	A request from you; it can also audit existing flows and campaigns	The page says Composer does not send or publish on its own; you review and approve before a message sends or a flow goes live
Klaviyo Flows AI	A flow draft with a recommended trigger, filters and actions, per its help page	A description you type	You review the draft and set the flow to Live yourself; the page says the feature is only for paid accounts
Omnisend Agent	Subject lines, audience segments from plain-language descriptions, and signup forms, per its help page	Your request inside the product	The page describes review steps for suggestions, and does not say whether anything sends without sign-off
Shopify Campaign Autopilot	Recommended marketing actions, and branded emails and automations	A recommendation from Shopify	Nothing runs without your approval; announced June 2026 as early access for qualifying stores
Tranthor	The audience and message for a retention play	A moment it finds in your store data	The first run of every playbook; auto-send is off by default
Manual	Whatever you write	You	Everything

Read that table as a split of who starts the work. Every tool in it has a review step. The difference is whether you have to know what to ask for, or the tool brings you something to review. Shopify's Autopilot also brings recommendations, so Tranthor is not the only tool that does. For side-by-sides, see Tranthor vs Klaviyo, Tranthor vs Omnisend and Tranthor vs Shopify Email.

How Each Tool Credits Revenue

Attributed revenue is the figure most retention reports lead with. It shows which orders a message is credited with, under a rule the tool sets. The rules differ.

	Klaviyo	Omnisend
Model	Last touch: the last eligible touchpoint before the purchase gets the credit, per its attribution page	Last touch, but only if the customer engaged with the message, per its attribution page
What counts as engagement	Email clicks and opens, and text message clicks, among others	Email opens and clicks; for SMS, only clicks
Default windows	Email clicks, email opens and text clicks: 5 days (new accounts)	Email: 7 days; SMS: 24 hours
Can you change it?	Yes	Yes
Machine opens	Machine-open settings are adjustable	Opens from Apple Mail Privacy Protection count as engagement by default and can be excluded
Holdout testing	Global holdout groups exist, set up by hand, and require at least 400,000 total profiles (help page)	The attribution page does not mention holdout groups

The Klaviyo windows are for new accounts, and its help page notes they can be edited. Check your own account settings rather than assuming the defaults.

None of this makes the figures wrong. It makes them credit, not cause. A customer who was about to reorder anyway, and happened to click an email, is credited to the email. To see what a program added, compare against customers you did not message.

In Tranthor, results are shown as attributed revenue per recipient. Lift is shown only for campaigns where you set up a holdout, and only once both groups reach 100 customers; below that it says there is not enough data yet. Holdouts are opt-in, not on by default, and lift is a plain difference between the groups rather than a significance test. See how results are measured.

Retention Software by Situation

Your situation	Start with	Check first
Someone owns lifecycle marketing and wants full control	Klaviyo or Omnisend	Who maintains flows in six months, and how billable contacts are counted; see Klaviyo alternatives for Shopify and Omnisend alternatives for Shopify
One marketer, a few flows, mostly email	Shopify's built-in tools	Whether each audience can be built as a segment; see Shopify CRM
WhatsApp is central in your market	Shopify Messaging, Klaviyo, or a WhatsApp-specific tool	Per-message rates and delivery by country; see Klaviyo alternatives for WhatsApp marketing
Nobody owns the second order	A retention tool that finds the moment and drafts the campaign, such as Tranthor	That it runs the play you need today, and what waits for your approval
You are still learning what works	Manual retention, one moment at a time	A written signal, audience, exclusion list and outcome for each moment

For a comparison of operating models beyond retention, see best ecommerce CRM software, or the overview of AI CRM for ecommerce.

Where Tranthor Fits

Tranthor is an AI retention team and autonomous CRM for ecommerce. It reads a connected store, finds moments such as a second purchase, a lapse or churn risk, drafts the audience and message, and sends within limits you approve.

Fits: Shopify brands with no dedicated CRM team that would rather review a prepared campaign than build one.
How control works: The first run of every playbook is drafted for your approval. Auto-send is off by default and is switched on per playbook after one approved run. Limits you approve cover contact frequency, spacing, daily sends and discount percentage. Autonomous sends skip people who have unsubscribed or have not opted in. See what the owner controls.
Channels: Email, SMS and WhatsApp, where connected and configured. WhatsApp messages a brand starts need pre-approved templates.
Limitation: It runs second-purchase, reactivation, churn-risk, next-product and VIP plays today. Cart recovery is on the roadmap, so keep your existing abandoned-cart flow. It does not replace a sales CRM, and it will not suit a store with a lifecycle marketer who enjoys building flows.

A 30-Day Pilot

Test any tool the same way: one play, a fixed window, and two example customers.

Know your starting point. The free retention check works out your repeat purchase rate from three numbers, without a signup. Write the figure down.
Pick one play. For example, the step from first to second order, as described in Shopify second purchase campaign.
Pick two test customers. One who should receive the message, and one who should be excluded because they unsubscribed or just reordered. Ask the vendor to show both.
Keep sending in review until you have read who is eligible and what each message says. Turn on automatic sending only after that.
Hold back a random group of eligible customers, and compare repeat orders against them at the end of the window. Reports of orders credited to a message do not replace this.
Decide before you start what result would make you widen the pilot, and what would make you stop.