Selling on Amazon and Shopify: keep the channel data apart
Tag every click for one destination: UTM parameters for Shopify and GA4, an Amazon Attribution tag for Amazon. Amazon's brand halo stays on Amazon's side, and neither tool measures spillover between the stores, so test it with a pause.
By Joris van Huët, Founder & CEOPublished 5 min read
Run the numbers for your store: the free ad platform over-reporting checker.
Give every click one home. A click that lands on your Shopify store should carry UTM parameters that Shopify and GA4 read, and a click that lands on Amazon should carry an Amazon Attribution tag, which Amazon credits for 14 days on a last-touch basis. Neither tool reports how a campaign pointed at one store moves sales in the other, so treat that halo as unmeasured until a pause test says otherwise.
How do you tag traffic so each click has one home?
On the Shopify side, Google's URL builder page says to always use utm_source, utm_medium and utm_campaign, and that values are case sensitive, so utm_source=google and utm_source=Google are different values. Shopify says traffic that arrives with utm_campaign in the URL is attributed to marketing.
On the Amazon side, Amazon makes the tag. Each ad group gets a unique attribution tag, and you paste it into the ad's destination URL in place of the ASIN or Store URL. You choose the ad group name, so give it the same name as the UTM campaign. That shared name is your join key.
Where does halo show up, and where doesn't it?
On Amazon, brand halo has a narrow meaning: conversions on other products of the same brand after a tagged click. The guide says brand halo metrics exclude the promoted products, and that total conversions equal promoted conversions plus brand halo conversions. Amazon's total product sales therefore include products you didn't promote. That halo stays on Amazon's side of the ledger. It isn't Shopify lift, and it doesn't belong in Shopify's attributed revenue.
The spillover that matters runs across stores, and neither tool measures it. If a campaign pointed at your store leads a shopper to buy on Amazon later, there's no tagged click on the Amazon side, so Amazon Attribution has no click to credit. Shopify's marketing reports cover Online Store channel orders, so they show nothing either. The pages cited here give no figure for how big that spillover is, and this page cites none.
How do you compare the channels without mixing the rules?
Keep each tool's credit on its own line with its window and model: Amazon's last-touch window, and on Shopify the most recent click within the past 30 days for marketing activity reports. Shopify also offers an Any click model that gives full credit to every channel clicked. It says that model allocates more credit than orders you've received, so it is best used to analyze a single channel, and that you can use it to reconcile attribution reported by each channel.
What is the free check?
Run this every week, and once before a launch:
- Audit the tags. Click each live ad link in a private window. A Shopify-bound link should show utm_source, utm_medium and utm_campaign in the address bar. An Amazon-bound link should carry an attribution tag. A link with neither is untracked, and Google says missing UTM parameters show up as (not set) in GA4 reports.
- Match the names. Each UTM campaign should have one Amazon ad group with the same name, spelled the same way.
- Reconcile clicks. Compare Amazon Attribution clicks with the ad platform's clicks for the Amazon-bound ads. Amazon's guide says you may see a 10-20% gap against publisher click data, which is Amazon's own statement and not an independent measurement, and lists checks if it is more than 20%: the same date range in both, and a tag that isn't shared across other creatives, URLs or event trackers. Do the same for Shopify sessions per utm_campaign against the store-bound ads' clicks and write the gap down, because the Shopify pages cited here give no expected range.
- Pause and read. Pause the store-bound campaign for two weeks and leave the Amazon-bound ads running. In Brand Analytics, which needs a Professional selling account and Brand Registry, the Search Query Performance dashboard lists the keywords shoppers use to find your brand, with query volume, impressions, clicks, cart adds and purchases. Compare your brand-name queries and purchases with the two weeks before.
Pass: every link has one home, every UTM campaign has one matching ad group name, Amazon clicks sit inside Amazon's 10-20% band, and brand-name purchases on Amazon don't move when the store-bound campaign pauses, which suggests no spillover large enough to see. Fail: an untracked link, a campaign name with two spellings, Amazon clicks more than 20% apart, or brand-name purchases that fall during the pause, which is spillover to report as its own line and not as Shopify lift. A pause is an observation, not an experiment, so promotions and seasons can move Amazon queries too.
Sources, 30 September 2026: URL builders: Collect campaign data with custom URLs (Google, page read 30 September 2026); Your complete guide to Amazon Attribution (Amazon Ads, page read 30 September 2026); Measuring marketing performance (Shopify, page read 30 September 2026); Amazon Attribution: Get started with advertising analytics (Amazon Ads, page read 30 September 2026); Marketing reports (Shopify, page read 30 September 2026); Amazon Brand Analytics (Amazon, page read 30 September 2026)
Related answers
Frequently asked questions
How do I track Amazon and Shopify sales from the same ad?
Give each click one destination and one tag. Shopify-bound links carry utm_source, utm_medium and utm_campaign. Amazon-bound links carry an Amazon Attribution tag pasted into the destination URL. Use the same campaign name on both sides so you can join the exports.Does Amazon brand halo count as Shopify sales?
No. Amazon's brand halo is conversions on other products of the same brand on Amazon after a tagged click. Shopify's marketing reports cover Online Store channel orders, so those Amazon sales don't appear there.How close should Amazon Attribution clicks be to my ad platform's clicks?
Amazon's guide says you may see a 10-20% discrepancy against publisher or ad server click data, and to troubleshoot if it is greater than 20%. Check the same date range in both and that the tag isn't shared across creatives or URLs.
Go deeper: Causal attribution, explained.
Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.
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Terms in this article
- AttributionAttribution identifies user actions that contribute to a desired outcome and assigns value to each. It reveals which marketing touchpoints drive conversions.
- Attribution ReportAttribution Report shows which touchpoints or channels receive credit for a conversion. It identifies which campaigns drive desired actions.
- ConversionConversion is a specific, desired action a user takes in response to a marketing message, such as a purchase or a sign-up.
- Holdout TestA holdout test is an experiment where a portion of the audience does not see a campaign. This measures the campaign's true incremental impact.
- ImpressionAn Impression counts each time an ad or content displays on a user's screen. It measures exposure, not engagement.
- IncrementalityIncrementality measures the true causal impact of a marketing campaign. It quantifies the additional conversions or revenue directly from that activity.
- Incrementality TestingIncrementality Testing measures the additional impact of a marketing campaign. It compares exposed and control groups to determine causal effect.
- UTM ParametersUTM Parameters are URL tags marketers use to track campaign effectiveness across traffic sources. They provide data for accurate campaign tracking and attribution in analytics platforms.