Google takes a cut of every Shopping bid. Here is the switch that stops it

SHOPIFY MARKETING E-COMMERCE

November 06, 2026

LAST UPDATED ON November 06 2026

Key Takeaways

Google's own comparison service, Google Shopping, places your Shopping ads by default and, in Google's words, ensures profitability by deducting a fixed percentage margin from each merchant bid. CSS providers put that margin at 20%.
Any store advertising in the UK or 20 other European countries can run the same Shopping ads through a third party Comparison Shopping Service instead, so the whole bid competes in the auction. Google Ads campaigns do not change.
A plain CSS costs from about £34 a month, so it pays for itself above roughly £170 a month of Shopping spend at a 20% saving, or £227 at a cautious 15%. The saving arrives as cheaper clicks or more impressions, never as a refund.
The switch is a request from the new CSS that an admin approves in Merchant Center. The two things that go wrong are placements beyond the search page and countries outside the programme, and both are checks, not obstacles.
The Shopping part of Performance Max benefits in the same way, because Performance Max product ads come from the same Merchant Center feed.
When we checked our own clients' Shopping accounts in November 2026, every one of them was still on Google's own CSS. We expect most UK Shopify stores are in the same position.

Quick Answer

A Google Shopping CSS, or Comparison Shopping Service, is the company that places your Shopping ads in Google's results. By default that company is Google Shopping, which deducts a margin from every bid before it enters the auction. Google calls it a fixed percentage; CSS providers put it at 20%. Move your Merchant Center to a third party CSS and the full bid competes, your campaigns stay exactly as they are, and the only cost is the CSS fee, from about £34 a month. For a store spending £1,000 a month on Shopping, that is worth up to £200 a month in bidding power, or £166 after the fee. The rest of this article explains why the margin exists, what the switch is worth to you, how to make it on a Shopify store and what to check so nothing disappears.

What is a Google Shopping CSS?
Why does Google take a cut of your Shopping bids?
How much is the switch worth?
Calculator: your saving and the right option
What a CSS costs and who provides one
How to switch a Shopify store to a CSS
What goes wrong on the switch
Does it work with Performance Max?
Can you run your own CSS?
What is changing in Europe and the UK
Why Matters Perspective
Frequently Asked Questions
Final Thoughts
Related Articles

What is a Google Shopping CSS?

A Comparison Shopping Service is a price comparison business that Google allows to place Shopping ads on behalf of the merchants it represents. Every Shopping ad shown in the UK and Europe is placed by a CSS, and the name of that CSS sits at the bottom of the ad in small text, as "By Google" or "By" followed by the provider's name. Most merchants have never chosen one, which means they are using Google's own: Google Shopping, which, in Google's words, "bids on behalf of merchants that it represents like any other CSS".

The programme exists in 21 countries. Google's list covers the United Kingdom, Switzerland and 19 EEA countries including Ireland, France, Germany, Spain, Italy and the Netherlands. Outside those countries there are no CSSs and none of this applies, which matters for stores that also advertise in the United States, as we explain below.

Three facts from Google's own documentation decide everything that follows. First, your Merchant Center account determines which CSS your Shopping ads and free listings belong to; your Google Ads account does not need to change. Second, a Merchant Center account can be linked to one CSS at a time. Third, clicks on the "By" link under an ad are free of charge for the CSS, which is why providers like the arrangement.

Why does Google take a cut of your Shopping bids?

Because the European Commission made Google's comparison service stand on its own feet. On 27 June 2017 the Commission fined Google €2.42 billion for favouring its own comparison shopping service in search results, and the Court of Justice upheld that fine in September 2024. Google's response was to separate Google Shopping into a comparison service that competes with other CSSs for the ad slots, and to let any approved CSS place ads for merchants.

Here is the part most merchants never read. Google's Merchant Center Help says: "The European Commission requires Google Shopping to be independently profitable in EEA countries" and that "Google Shopping currently ensures profitability by deducting a fixed percentage margin from each merchant bid". The margin "is included in the CPC paid by the merchant" and is charged only when someone clicks. In plain English: when you bid £1.00 through Google's own CSS, something less than £1.00 goes into the auction that decides which ads show, and the difference is Google Shopping's income.

Google does not publish the percentage. The CSS industry has quoted 20% since the programme began, and a third party CSS has no such margin, because it earns its money from a flat fee instead. So the same £1.00 bid competes as £1.00 through a third party CSS and as about £0.80 through Google Shopping. That is a 25% difference in bidding power for the same money, or, if you prefer to keep your positions and cut your bids, a cost per click up to 20% lower.

Where a £1 Shopping bid goes. Illustrative; the margin figure is the industry's, from Google's description of a fixed percentage margin. Source: Google Merchant Center Help, read 6 November 2026.

One honest caveat. The 20% is the providers' figure, not Google's, and providers sell CSS services. We have found no independent measurement published since the programme's early years, which is why our calculator below shows a cautious 15% beside it.

How much is the switch worth?

Take a store spending £1,000 a month on Shopping ads through Google's own CSS. At a 20% margin, around £200 of that money never reaches the auction. Move the Merchant Center to a third party CSS at £34 a month and you have two choices: leave your bids alone and get about a quarter more auction power for the same spend, or lower your bids by a fifth and keep the same positions for about £200 a month less. Either way the gain is roughly £200 a month and the cost is £34, so the net is £166 a month, or £1,992 a year, before anything else improves.

The arithmetic scales in a straight line, which gives a simple rule: a CSS pays for itself once your Shopping spend passes the fee divided by the margin. At £34 a month that is £170 of spend at 20%, or £227 at 15%. Below that, stay where you are. The table shows the numbers at the spend levels we see most often.

Monthly Shopping spend	Gain at 20%, net of £34 fee	Gain at 15%, net of £34 fee
£250	£16 a month	About £4 a month
£500	£66 a month	£41 a month
£1,000	£166 a month	£116 a month
£2,500	£466 a month	£341 a month
£5,000	£966 a month	£716 a month

Two things the numbers hide. The gain arrives as more impressions or cheaper clicks, which you see in your Google Ads reports over the following weeks; nobody sends a refund. If your campaigns use automated bidding with a target return on ad spend, Google will spend the extra power for you, so the result shows up as more sales at the same target rather than a lower bill.

Calculator: your saving and the right option

Enter your monthly Shopping spend and the CSS fee you have been quoted. The calculator shows what you are giving away, what is left after the fee, where the breakeven sits, and which of our three options fits your situation. It works for any provider, not only the ones we name.

CSS savings calculator

Monthly spend on Google Shopping and Performance Max (£) Monthly CSS fee (£). The cheapest we have found is about £34

Who looks after your Google Ads?

I do it myself An agency or a freelancer Nobody really, it runs itself

Do you advertise outside the UK and Europe?

No Yes

Results

Bidding power you are giving away at 20%: £200 a month, £2,400 a year

At a cautious 15%: £150 a month, £1,800 a year

Net of the CSS fee: £166 a month at 20%, £116 at 15%

A CSS pays for itself: above £170 a month of Shopping spend at 20%, or £227 at 15%

Our suggestion: Offer B: the Shopping tune up, £195 plus VAT, one off.

The switch plus a Merchant Center and feed health check, a Performance Max structure review and the 30 day report. At £1,000 a month the CSS alone is worth around £200 a month, so the tune up pays for itself quickly. Our promise: if it has not paid for itself in 60 days we switch you back, free.

Book a 30 minute call

The calculator runs in your browser and sends nothing to us. The saving shows up as cheaper clicks or more impressions, not as a refund, and only the Shopping part of Performance Max benefits.

The three options the calculator chooses between are described in full in the Why Matters Perspective section: a free switch, a one off tune up at £195 plus VAT, and managed Shopping from £650 a month plus VAT.

What a CSS costs and who provides one

Google keeps a directory of CSS partners and there are far more than the handful some salespeople claim. Prices fall into three shapes: a flat monthly fee per Merchant Center, a bundle that includes a feed management tool, and a share of ad spend, which we would avoid because it recreates the problem you are leaving. Two examples we checked in November 2026:

Provider	Price	What you get
AdStrong	€39 a month per Merchant Center, about £34, plus VAT	CSS in all 21 countries, 30 day free trial, cancel monthly
Shoptimised	£119.99 plus VAT a month, quoted to us in November 2026	CSS for three stores plus a feed management tool, so £40 a store if you fill all three
Google Shopping (the default)	No fee	The margin on every bid instead

We have no commercial relationship with either company and earn nothing if you sign up with them. If that changes we will say so here. Our own clients go onto a plain CSS at the provider's price, with no markup, because the fee is not where the value is.

How to choose: pick a provider that is opted in to every placement (the next section explains why), that lets you leave monthly, and that charges a flat fee. Ignore claims about extra traffic from the "By" link; those clicks go to the provider's comparison site, and whether any reach you depends entirely on how that site is run.

How to switch a Shopify store to a CSS

The switch itself takes minutes. The checks around it take an hour, and they are the whole difference between a switch that quietly works and one that quietly breaks something.

Choose the provider and sign up. You will give them your Merchant Center ID, which is the number at the top right of Merchant Center.
The provider sends a switch request to your Merchant Center. Google's process is that the new CSS initiates it and a Merchant Center admin approves or declines it. Nobody else can move your account.
Ask for an in place switch. Some providers prefer to move your account under their own multi client account. Shopify's Google and YouTube app only links to a stand alone Merchant Center, so keep your account stand alone or your product sync from Shopify can break.
Approve the request in Merchant Center, then check the Account access page to confirm the provider's access is what you agreed.
Leave Google Ads alone. Campaigns, budgets and bidding strategies stay as they are. Watch impressions and cost per click over the next two weeks.
Decide what to do with the extra power. Keep your bids and take the extra impressions, or lower manual bids by about a fifth and bank the saving. With target ROAS bidding, do nothing and let the system spend it.
Compare after 30 days: impressions, clicks, average cost per click and conversions against the 30 days before. That comparison is the only proof that matters.

What goes wrong on the switch

Two things, and both are in Google's own documentation. First, placements. Shopping ads do not only appear on the search results page; they appear on the Shopping tab, in Images, on YouTube and as dynamic remarketing on the Display network, and Performance Max uses all of them. A CSS has to be opted in to those placements for the merchants it represents. Google's guidance is blunt: if the new CSS is not opted in, your products will only appear on general search results and will stop being served on other surfaces. The ads do not fade over time; they are missing from the first day. So ask the provider, in writing, before you approve the request.

Second, countries. The programme covers 21 European countries and nothing else. A Merchant Center linked to a third party CSS stops serving ads and listings for any country outside the programme, because that CSS cannot place them there. A UK store that also sells to the United States needs a second Merchant Center that stays with Google Shopping for the US, and both can link to the same Google Ads account. On Shopify that means the second account gets its feed through a feed app or a scheduled feed rather than the Google and YouTube app, which connects a store to one Merchant Center.

A third thing is cosmetic but worth telling the owner: the small print under your ads changes from "By Google" to the provider's name. Nobody has shown that shoppers care either way, and the provider's name cannot be yours, because Google's rules stop a CSS sharing a name with a brand whose goods it lists.

When a CSS competes with your own campaigns

Some CSS companies do not wait to be hired. They join affiliate networks, advertise merchants' products on Google Shopping under their own CSS name, and collect the affiliate commission on every sale. We ran into this while managing Awake Organics' affiliate programme on Awin. Paid search was not an allowed channel for publishers, yet a steady run of orders arrived through Redbrain, a CSS that works exactly this way. Its Shopping ads were competing with the Shopping campaigns we were running for the same products, so the brand was paying twice for the same clicks: once for its own ads and again in commission on sales its own campaigns would have won. We asked them to stop, and when that did not work we removed them from the programme.

The lesson for any store with an affiliate programme: look at who is sending the orders, and if a CSS or price comparison publisher is among them, decide whether you want it there. If you run your own Shopping campaigns, you usually do not. If you run none, a commission only CSS can be a reasonable way to get product ads shown, as long as you know that is what you have agreed to.

Does it work with Performance Max?

Yes, for the Shopping part. Performance Max product ads come from the same Merchant Center feed as standard Shopping campaigns, so they are placed by whichever CSS the account is linked to and benefit from the full bid in the same way. The non product placements inside Performance Max, such as the Search, Display and YouTube ads built from your assets, are not part of the CSS programme and do not change. If most of your Performance Max spend goes on product listings, which is the case for most Shopify stores, enter the whole budget in the calculator; if it is split, enter the product share.

Can you run your own CSS?

A brand cannot, and an agency can, with effort. Google's programme requirements say a CSS must run a genuine comparison website that shows products from at least 50 distinct merchant domains in every country it serves, with a search box, sorting and filtering by price and at least one other dimension, open to anyone without signing up, backed by a business registered in a programme country. Businesses that mainly run a marketplace on their own domain are excluded, and a CSS cannot share a name or logo with a brand that sells physical goods it lists. So a store cannot be its own CSS, and "By Your Brand" under your ads is not an option.

For an agency the maths is different. White label providers run the comparison site for you under your name, so the agency's clients see "By" the agency on their ads and the free clicks land on a site showing the agency's clients' products. We are looking at exactly that. It is an annual commitment, so our advice to ourselves is the same as our advice to you: put the stores on a plain CSS first, measure for two months, then decide.

What is changing in Europe and the UK

The fight over comparison shopping is not over. On 23 July 2026 the European Commission fined Alphabet €460 million under the Digital Markets Act for continuing to favour its own services in search, with a further €430 million for Google Play, and ordered changes to how comparison services appear. The layout Google proposes for Shopping results in the EEA is still being argued over; twelve CSS providers wrote to the Commission in September 2026 warning that a closed Google box would push merchants back to Google's own service. Nothing has been decided.

None of that applies to the UK, which left the EU and is not covered by the Digital Markets Act. The CSS programme carries on in the UK as before. The UK's own regulator is moving too: on 10 October 2025 the Competition and Markets Authority designated Google with strategic market status in search and search advertising, which gives it the power to impose conduct requirements, although it has said the designation introduces no immediate requirements. We will update this article when either side changes the rules. For now the margin exists, the switch works, and the saving is real.

Why Matters Perspective

We only looked into this properly in November 2026, after a CSS provider's sales call, and the first thing we did was read Google's documentation rather than the provider's slides. When we then checked our own clients' Shopping accounts, every one of them was still on Google's own CSS, including a client spending over £1,000 a month on Shopping, for whom the switch is worth around £200 a month. We are moving them first, at the provider's price with no markup, and their before and after numbers will appear here once we have 30 days of data.

Three ways we can do the same for you. Offer A, the free CSS switch: we send the request, get it approved, check placements and countries, advise on the bid change and send you a 30 day comparison. You pay the CSS provider about £34 a month after the free month; you pay us nothing. For any store spending £250 a month or more. Offer B, the Shopping tune up, £195 plus VAT, one off: the switch plus a Merchant Center and feed health check (disapprovals, titles, categories, GTINs and missing attributes), a Performance Max structure review and the 30 day report. For stores spending £500 or more that run their own ads. Offer C, Managed Shopping, from £650 a month plus VAT: we run the feed, the campaigns and the bidding every week, with the CSS included at our cost, billed a month in arrears with no contract. For stores spending £1,000 or more.

Two promises come with all three. If the switch has not paid for itself within 60 days, we switch you back, free; switching back is just another request. We also disclose any commission a provider pays us, which today is none. Why Matters is a Shopify Select partner with Verified Skills across development and marketing, our prices are published, and retainer clients are billed one month in arrears and can leave at any time. To start, book a 30 minute call or email us.

Frequently Asked Questions

What is a CSS in Google Shopping?

A Comparison Shopping Service is a price comparison company that places Shopping ads on Google on behalf of the merchants it represents, and every Shopping ad in the UK and Europe is placed by one. Google's own comparison service, Google Shopping, is the default, and the name of the CSS appears in the small print at the bottom of every ad. Which CSS you use is decided by your Merchant Center account, not by your Google Ads account.

Does Google really keep 20% of my Shopping bids?

Google's Merchant Center Help says that Google Shopping ensures profitability by deducting a fixed percentage margin from each merchant bid, and that the margin is included in the cost per click you pay. Google does not publish the percentage. CSS providers have quoted 20% since the programme began. Treat 20% as the industry figure and 15% as a cautious one.

Do I have to change my Google Ads campaigns to use a CSS?

No. Google says Google Ads accounts do not need to be switched, because the Merchant Center account decides which CSS your Shopping ads belong to. Campaigns, budgets, bidding strategies and conversion tracking stay as they are. The only visible change is the name of the CSS under your ads, plus your decision to keep your bids or lower them by about a fifth.

Does the CSS discount apply to Performance Max?

Yes, for the Shopping part. Performance Max shows product ads from your Merchant Center feed in Shopping placements, and those are placed by whichever CSS your Merchant Center is linked to. The other placements in a Performance Max campaign, such as Search, Display and YouTube ads that are not product listings, are unaffected either way.

Can my Shopify store become its own CSS?

In practice, no. Google requires a CSS to run a genuine comparison website that lists products from at least 50 different merchants in every country it serves, with search, sorting and filtering, and a CSS cannot share a name with a brand whose goods it lists. A store can use any CSS, and an agency can run one through a white label provider, but a brand cannot be its own.

What does a Google CSS cost in the UK?

From about £34 a month for a plain CSS with a free trial and no contract, up to £119.99 plus VAT a month for a package covering three stores with a feed management tool. Google's own CSS has no fee, but you pay through the margin on every bid. The fee only makes sense once your monthly Shopping spend is above roughly £170 at a 20% saving, or £227 at 15%.

Does this apply outside the UK and Europe?

No. The CSS programme runs in the UK, Switzerland and 19 EEA countries, and only there does the margin exist. If your Merchant Center also carries products for the United States, Canada or Australia, those ads will stop once the account moves to a third party CSS, so they need a second Merchant Center that stays with Google Shopping. Nothing changes for advertisers who only sell in the UK and Europe.

Final Thoughts

Google Shopping is a comparison service that keeps a margin of your bids because a court made it pay its own way. Every other CSS charges a fee instead, and for any store spending more than a couple of hundred pounds a month on Shopping ads the fee is the smaller number. Your campaigns do not change, the switch is one approved request, and the proof is in your reports within a month.

Do the two checks, placements and countries, before you approve the request, and ask for an in place switch so your Shopify feed keeps flowing. Then run the calculator above, pick the option that fits, and we will do the rest.

Written by the Why Matters team. Why Matters is a Shopify agency in Brighton and a Shopify Select partner with Verified Skills across development and marketing, and a Klaviyo, Recharge, Awin, Meta and TikTok partner. We design, build and grow Shopify stores for UK brands, with our prices published and a 3 month guarantee on every development project.About Why Matters

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