Duplicate customers are one of the most common data problems in Shopify, and one of the easiest to ignore.
A shopper checks out as a guest, then comes back and creates an account. Someone buys in store on your POS, then again online. An email typo, a nickname, or a social login spins up a second profile. Each one looks harmless. Over time they add up.
The cost is hidden but real. Split order histories make your best customers look average, so lifetime value can read well below the truth. Segments miss people who should qualify. Automated flows email the same person twice. And you pay your email platform for contacts that are really just one customer counted two or three times.
Below we compare the five best ways to clean them up: four dedicated apps and Shopify's own built-in merge. We look at how each one finds duplicates, how it merges them, what it costs, and who it suits best.
The five apps, reviewed
Singulary
Editor's PickSingulary scans your entire customer list and finds duplicates by name, email, phone and address. Every merge runs through Shopify's official Customer Merge API, so orders and history are preserved, and you decide field by field what to keep. It streams through tens of thousands of customers without slowing down, and paid plans are priced by customer count rather than a monthly merge limit, so a big one-time cleanup never costs extra.
Pros
- Unlimited merges on every paid plan
- Field-level control over the merged record
- Uses Shopify's official Merge API
- Scales to tens of thousands of customers
- Has earned "Built for Shopify" badge
- Scores 5/5 on 7 customer reviews
Cons
- No Klaviyo sync — see UnifyMate
- No B2B account linking — see Doppelganger
- Cleans up duplicates rather than preventing them
MergeGuard
MergeGuard provides automatic detection. Pricing is based on merges per month — 100 on the entry plan, up to 500 on the top tier — which suits a steady trickle of duplicates more than a large backlog. Plans start at $29 a month.
Pros
- Provides automatic detection
- Price based on merges per month
Cons
- Merges are capped per month — a large backlog gets expensive
- Higher starting price ($29/mo) than most here
- No customer reviews
UnifyMate
UnifyMate's standout feature is real-time Klaviyo sync: when you merge two customers, the change flows straight into Klaviyo, so your marketing stays accurate. None of the other apps here do that, Singulary included. It offers unlimited merges on a single flat plan at $24.99 a month, and the free tier includes the Klaviyo sync. If your marketing runs on Klaviyo, that alone can make it the right pick.
Pros
- Real-time Klaviyo sync — unique here
- Unlimited merges on one simple $24.99 plan
- Klaviyo sync included on the free tier
Cons
- No B2B account linking
- No customer reviews
Doppelganger
Doppelganger does something the others don't: it can link two accounts without merging them. That's handy for B2B, where several buyers belong to one company but should keep separate logins. It's also the cheapest paid option at $5 a month (free under 50 orders a month), and it has a track record of real merchant reviews — though they're mixed.
Pros
- Links accounts without merging — unique here
- Lowest paid price ($5/mo)
- Established, with real merchant reviews
Cons
- Scores 3.2 on 6 customer reviews
- Free tier is limited by monthly order count
Shopify's built-in merge
Since 2024 you can merge two customer profiles right inside Shopify admin, for free, using the same official API the paid apps use. The catch is that it does no detection. You have to already know which profiles are duplicates, and you merge them one pair at a time — fine for a few, impractical for thousands. There's no search by phone or address and no bulk merge.
Pros
- Free and built in — nothing to install
- Official, safe merge that preserves orders
Cons
- No detection — you find the duplicates yourself
- One pair at a time; no bulk merge
- Impractical beyond a small number of duplicates
Feature comparison
| Feature | Singulary | MergeGuard | Doppelganger | UnifyMate | Shopify Native |
|---|---|---|---|---|---|
| Auto-detection | ✅ | ✅ | ❌ | ✅ | ❌ |
| Bulk merging | ✅ | ✅ | ❌ | ✅ | ❌ |
| Confidence scoring | ✅ | ✅ | ❌ | ❌ | ❌ |
| Klaviyo sync | ❌ | ❌ | ❌ | ✅ | ❌ |
| Data health | ✅ | ❌ | ❌ | ❌ | — |
| Built for Shopify | ✅ | ❌ | ❌ | ❌ | — |
| Reviews score | 5.0 ★ | — | 3.9 ★ | — | — |
| Starting price | Free / $9 | $29/mo | $5/mo | $24.99/mo | Free |
Frequently asked questions
What's the best Shopify app to merge duplicate customers?
It depends on your goal. For cleaning up a large backlog with accurate detection and unlimited merges, Singulary is the best all-round pick. If real-time Klaviyo sync matters most, choose UnifyMate. For just a few known duplicates, Shopify's free built-in merge is enough.
Can you merge duplicate customers in Shopify for free?
Yes. Shopify's built-in merge is free, but it is manual and does no detection. Most third-party apps, including Singulary, MergeGuard and UnifyMate, also have a free tier with a small number of merges so you can test before paying.
Is merging duplicate customers in Shopify reversible?
A merge is permanent. Shopify's Customer Merge API has no unmerge endpoint. Some apps let you export a pre-merge backup, but restoring it creates a new customer record rather than bringing back the original customer ID and its order links. Always preview a merge before you confirm it.
Does Shopify have a built-in way to merge duplicate customers?
Yes. Since 2024 you can merge two customer profiles directly in Shopify admin using the official API. It works for a handful of duplicates, but it does not find them for you and only handles one pair at a time, which is impractical for stores with thousands of customers.
Why do duplicate customers happen in Shopify?
The usual causes are guest checkout followed by account creation, POS sales that don't match an online profile, CSV or wholesale imports, and email or phone variations such as typos and nicknames. Duplicates split order history, understate lifetime value, break segments, and can inflate the contact counts you pay your email platform for.
Find your duplicates for free
Scan your entire Shopify customer base, see every duplicate with a match-score breakdown, and merge on your terms. The free plan includes five merges.