Google CSS Partners: The ultimate guide

In 2017, the European Commission imposed a record fine of €2.4 billion on Google for violating EU competition rules. The Commission found that Google had given its own shopping service an unfair advantage in search results by displaying its own results at the top. This excluded comparison sites from competing on equal terms. 

Industry opinions differ on whether this ruling was fully justified, but it put Google under intense pressure to make changes. If Google failed to take significant steps to open its platform to comparison sites, the fine could have increased by around 5% of its global annual revenue.

To address this and comply with EU regulations, Google created the Google CSS (Comparison Shopping Service) Program, enabling comparison sites to run Shopping ads on Google’s search results page, thereby creating a more open and competitive environment. As part of this initiative, Google also introduced a 20% margin advantage for CSS partners, so that these sites could compete more fairly with Google’s own service.

A Google CSS partner (Comparison Shopping Service partner) is a comparison website (a website that collects prices from different webshops) that can place Google Shopping ads on behalf of online retailers. Instead of running campaigns directly through Google’s own CSS, advertisers can work with an independent CSS partner to access the same ad placements, often at a lower cost.

Google Shopping is itself a Comparison Shopping Service, visible under the “Shopping” tab in Google search results. To comply with EU competition regulations, Google separated its own CSS into a standalone company (Google Shopping). This change opened the market to other CSS partners across Europe, allowing them to run Shopping ads for merchants.

When you advertise via a CSS partner like Producthero, your Shopping ads look identical to ads placed via Google’s own CSS. The only difference is that, instead of a link with "from Google", there is a link "From [CSS name]" at the bottom of the ad. When clicking on the advertisement, the visitor is simply redirected to the webshop for which the CSS advertises. Only when clicking on the "From [CSS name]" link does the searcher go to a CSS comparison page

To ensure fair competition, Google gives CSS partners like Producthero a built-in 20% CPC discount compared to using Google Shopping (Google’s own CSS) directly. This means advertisers can reach the same audience while spending less or get more impressions with the same budget.

CSS partners can place Shopping ads on Google on behalf of sellers in Switzerland and in countries that are part of the European Economic Area (EEA). CSS Shopping adverts are currently available in the following 21 countries: Belgium, Denmark, Germany, Finland, France, Greece, Hungary, Ireland, Italy, the Netherlands, Norway, Austria, Poland, Portugal, Romania, Slovakia, Spain, the Czech Republic, Sweden, Switzerland and the United Kingdom.

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‍What about Producthero?‍

‍Producthero is one of the few CSS partners that is active in all the CSS program countries.

The Comparison Shopping Service (CSS) program has evolved over the years. In its early days, the program even reimbursed advertisers for part of their advertising spend. This incentive encouraged rapid adoption of CSS partners, but it was only a temporary measure.

Today, the 20% CPC discount remains in place, and it is expected that it will continue for an extended period of time. This means advertisers can still save significantly by using a CSS partner like Producthero instead of Google’s default CSS.

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What about Producthero? As one of the largest international Premium CSS partners, Producthero is well-positioned to adapt to any future changes in the program. Our dedicated team of developers and shopping specialists ensures we can act quickly and effectively. More than 15,000 webshops already trust us to optimize their Shopping campaigns. Furthermore, we have no cancellation period, so you may cancel the advertising at any time via our CSS.

You will find the information you are looking for on the Google CSS program on the Google CSS Partner Portal. You will also be able to compare the different CSS partners there.

You will find more information on how it works on the Google support page.

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A CSS partner can place Shopping ads on Google on behalf of the merchants they represent. This means you’re not limited to using Google’s own CSS

To start running Shopping ads via a Google CSS partner, you need to complete two key steps:

1. Associate your Merchant Center account with your chosen CSS partner

Your Google Merchant Center account must be linked to a CSS partner account (e.g., Producthero). This is a technical change that can be completed with just one click in your Google interface. Producthero can initiate this request for you. You simply need to give your consent.

2. Continue or launch your Shopping campaigns in Google Ads

Once the Merchant Center is linked, you can continue your existing Shopping campaigns or create new ones. No additional setup required. The only difference: your ads will now display “by Producthero” instead of “by Google” and benefit from a 20% margin advantage in ad auctions.

‍What about Producthero?
It is extremely easy to convert a Merchant Center to Producthero as well as to place products on our site. You can do this here: https://producthero.com/google-css

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This mainly depends on the agreement between the CSS partner and Google. If there is no agreement in place, Google’s support staff and account managers will no longer have access to your campaigns. If, on the contrary, there is an agreement in place, Google can continue to provide support. 

For larger advertisers used to receiving assistance and support from a Google account manager, support may become less strategic unless the CSS partner is a Premium CSS Partner. Premium partners like Producthero have stronger connections with Google, meaning faster communication and continued access to strategic support.

‍What about Producthero?
Producthero has a waiver agreement with Google. This means Google employees can continue supporting your campaigns, even if you run them through Producthero CSS. Additionally, our CSS and Shopping specialists are also happy to assist you.

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A Premium CSS Partner is a Comparison Shopping Service that represents more than 500 merchants running Shopping campaigns. Because of their size, Premium partners receive enhanced support from Google, allowing them to offer a higher level of service and maintain closer communication with Google teams. 

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What about Producthero?
Producthero is a Premium CSS Partner. Thus, we benefit from stronger collaboration with Google

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Not all CSS partners operate in the same way, and the differences can significantly impact your experience. One key factor is how they handle questions or new feature tests. Premium CSS Partners receive more support from Google, which can translate into faster answers and better strategic guidance.

It’s important to note that the financial benefits from Google are the same for every CSS partner. The way these benefits are passed on to advertisers depends on the partner’s business model. 

Some run their own Shopping campaigns and buy traffic at their own expense, charging advertisers an agreed cost-per-click (CPC) fee. Others allow advertisers to connect their existing campaigns to their CSS for a possible fee, so the advertiser can directly enjoy the Google benefits for their existing campaigns.

The most important differences between CSS partners include:

1. The type of CSS: self-service, managed or outsourced
   Some operate as self-service platforms (you stay in full control), meaning you create and run your own Shopping campaigns and the CSS is simply linked to your account so you can benefit from the Google CSS advantages. Others offer a managed service, where the CSS partner handles your campaigns for you. In some cases, the CSS partner will even create and run its own Shopping campaigns to promote your products, and then charge you based on the costs or results, usually as a cost-per-click (CPC) or cost-per-sale (CPS) fee.‍
2. ‍The business model:
   This describes how the CSS partner charges you. Google requires that all products advertised through a CSS appear on that partner’s comparison shopping website. Beyond that, pricing can vary a lot. Some CSS partners charge a fixed monthly fee for being connected to their service, while others use a performance-based model, billing you per click (CPC) or per sale (CPS) generated through their ads.‍
3. The service that the CSS partner provides
   This is the type and quality of support you get. Some CSS partners offer minimal assistance, while others provide hands-on help and strategic advice. Premium CSS Partners get more direct support from Google.‍
4. The countries in which the CSS partner is active
   The CSS program is active in 21 countries. Not all partners are active within the 21 countries

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What about Producthero? We believe in the power of your own Shopping campaigns. Our focus is on helping merchants make their existing campaigns stronger and more effective. We do not recommend letting a CSS partner run campaigns on your behalf that aren’t truly yours. In our experience, these campaigns almost always compete directly with your own, despite what some may claim.

With Producthero, you pay a fixed monthly fee to list all your products on our comparison site. This gives you predictable costs and full control. We’ve seen that when working with partners who charge variable rates, expenses can rise quickly and unexpectedly, especially since all products must appear on the CSS site.

Plus, we back this with a fantastic customer support team and operate in all 21 countries where the Google CSS program is active, ensuring you get both expert guidance and maximum reach.

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In many cases, CSS partners allow you to continue managing your own campaigns. In this setup, your Merchant Center is linked to the CSS and remains connected to your Google Ads account. The CSS partner does not even need access to your accounts.

Some other CSS partners, usually agencies, offer to manage the campaigns for you. There are also CSS partners who run the Shopping campaigns themselves and charge you a cost-per-click (CPC) or cost-per-sale (CPS) fee. There is also a possibility that they are running their own campaigns, which may directly compete with your own.

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What about Producthero?
At Producthero, we believe in the power of your own campaigns, and our goal is to make them more effective. For this reason, we never run our own Shopping campaigns, unlike some other CSS partners whose campaigns can compete with yours.

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When you advertise through a CSS partner like Producthero, your bids are worth more in Google Shopping auctions. This is because Google’s own CSS (Google Shopping) deducts a 20% margin from your bid before it enters the auction, while third-party CSS partners pass your full bid through without any deduction.

Shopping campaigns work like auctions, where you choose the cost-per-click (CPC) you’re willing to pay. When you use a CSS partner, 100% of your bid enters the auction. With Google Shopping (Google’s own CSS), Google deducts 20% of your bid before it enters the auction, so only 80% of your original bid is counted.

In practical terms, this means you get more value for your money with a CSS partner. If you bid €0.80 through Producthero CSS, it’s treated the same in the auction as a €1.00 bid through Google Shopping. So, someone using Google Shopping would have to pay 25% more than you just to be on equal footing.

This is one of the most common questions from customers who have just switched. The so-called “20% discount on the CPC” is not a refund and won’t appear in your Google Ads account. It’s not a discount in the traditional sense. It’s a bidding advantage compared to Google’s own CSS.

The effect is similar to staying with Google CSS but increasing your bids by 25%. This advantage helps your products appear in better positions, enter more auctions, and be shown more often. In short, you should see an increase in the visibility of your Shopping campaigns without having to increase your bids. Or, if you prefer, you will be able to keep the same visibility for your products at a lower cost.

To illustrate how it works, here’s an example from an account that recently switched from Google CSS to Producthero CSS. For this test, we created an identical copy of the campaigns that were previously running via Google CSS, keeping all settings, bids, and targeting exactly the same. Only the CSS partner was changed.

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After the switch, the total number of clicks increased significantly, showing the direct impact of the 20% bidding advantage:

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The increase in clicks came alongside a lower CPC, meaning more traffic for less cost:

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There are two main ways to use the CSS bidding advantage:

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1. Increase your turnover (sales volume)

If your Shopping campaigns already have a strong ROI/ROAS and you want more volume (sales), keep your bids the same. With the 20% margin advantage, your ads will appear more often and get more clicks (like if you had manually increased your bids).

The extra impressions will often come from broader, less specific search terms (higher in the funnel), which typically means a lower click-through rate (CTR) and conversion rate. Performance may not stay exactly the same, but if you have room in your ROI and are aiming for growth, this strategy can help you scale.

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‍2. Improve your campaign profitability

If your ROI is tight and you want to reduce costs, lower your bids by 10–20%. Thanks to the 20% margin advantage, you can often keep your traffic volume the same while paying less per click.

We recommend that most advertisers start with this second strategy. By improving profitability first and maintaining volume, you create a solid base. Once you’ve stabilised costs, you can then explore increasing turnover in a controlled way.

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Even if your campaigns use automatic bidding in Google Ads (e.g., Target CPA or Target ROAS) instead of manual CPC, you will still benefit from the 20% bidding advantage once your account is connected to Producthero CSS.

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With automated bidding, you have less direct control over CPC and impressions, as Google’s algorithm adjusts bids to meet your goals. However, if you keep your CPA or ROAS targets unchanged, once the algorithm adapts to the new situation, you should see more conversions and revenue at the same CPA or ROAS.

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Alternatively, you can choose to set a lower CPA target or a higher ROAS target. This way, you can achieve the same conversions or revenue as before, but with a lower overall investment.

To advertise via a CSS partner, two steps are required:

1. Link your Merchant Center to the CSS partner.
2. Ensure all advertised products appear on the CSS partner’s comparison site.

You can either create a new Merchant Center linked to the CSS partner, or (recommended) switch your existing Merchant Center to them. Switching your current Merchant Center lets you keep running your existing campaigns without changes and preserves your Ad Rank (the quality score of products in your Merchant Center).

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What about Producthero?
Switching your Merchant Center to Producthero is quick and easy, and adding your products to our site takes just a few clicks. You can start here: https://producthero.com/google-css

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Yes, switching to Producthero CSS is a completely painless process. There is also no downtime for your campaigns. You will notice the effects in your statistics in the days following the switch.

Yes, you can test it, but it requires a well-structured setup. To run a test, you need to:

1. Create an additional Merchant Center and link it to the CSS partner.
   
2. Connect this Merchant Center to an exact copy of your current Shopping campaigns in Google Ads.

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When evaluating results, keep in mind:

• The new Merchant Center will start without an Ad Rank history, so performance may initially be lower until that score is built.
  
• The campaigns must use manual CPC bidding. If Enhanced CPC is enabled, it can distort the results.

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In practice, most advertisers who tested this with us eventually switched their original Merchant Center to the CSS partner, as the 20% bidding advantage became clear. Many skip the test entirely and switch directly—both to avoid the complexity of the setup and because results tend to be more representative with the original Merchant Center.

The short answer would be: no. The expanded answer would be:

Many CSS partners offer to run additional campaigns in addition to your private campaigns. This would increase visibility and improve results.

This is what Google has to say about this: “In a second-price auction, a seller never competes against himself on an offer. This rule is always applicable regardless of how many and which CSSs the seller uses. If two CSSs place bids on behalf of the same seller, the winning offer and the price paid by the winning CSS are the same as if these bids were placed by the same CSS.”

It is therefore not the case that if one works with multiple CSSs it increases the CPC for a product advertisement. Having multiple CSSs from this perspective, theoretically does not have to be harmful. Although one has to consider that the additional CSSs may win the auction in comparison to your private campaigns. This is therefore at the expense of your private campaign results. We have seen how the results of their own Shopping campaigns deteriorated at several webshops due to several CSS partners advertising for them.

We believe that a webshop that uses Shopping campaigns often does not want its private campaign results to deteriorate due to the fact that other parties are fishing in exactly the same pond. A webshop that has a high-quality and extensively optimised Shopping campaign is not expecting that CSS partners grab some of the clicks and conversions. And the webshop doesn't benefit much from such either. The CSS partner(s) who wish to advertise is also hoping to earn and will focus on the “easy” clicks (best products, specific terms and high conversion). The CSS partner also has to create a margin, so the webshop could possibly have created these conversions with its private campaigns for cheaper.

Google continues to write: “We do our best not to display the same offer (the same product offered by the same seller) multiple times. If we determine that the same product from the same seller has been uploaded by multiple CSSs, we will only display it once in the advert block. In rare cases where we cannot determine whether two offers are the same, they may both be displayed in the same Shopping advert block.”

A CSS can realise additional displays for you on other products other than the products that you are displaying. But you can do this yourself with your own account. Suppose you search for “washing machine” you will then receive a display with your own Google Ads account for a certain type of Samsung, for example, and a CSS partner in the same block can receive a display of your shop, of a different type. However, it is not that you can only achieve this by advertising via a Google CSS partner. You may, from your own Shopping campaign, simply have multiple products displayed in the same block.

In fact, we can conclude that connecting an additional CSS partner who advertises for you only leads to additional displays if:

1. The CSS presents offers on products that you do not do the bid yourself or offers higher on products where you would not have won the auction for a display with your bid to receive a display.
2. The CSS has a different product feed that (because the content is, for example, enriched with additional information) matches the product to the search term, while that was not the case with your feed.

In short, there is no difference between what an additional CSS connection could mean for generating additional displays in comparison to the possibilities that you have (bid optimisation, feed optimisation) to increase your visibility.

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What about Producthero?

Connecting an additional CSS partner offers nothing extra when compared to what an advertiser can do himself to improve the visibility and results of his campaigns. Our mission is to fully empower our customers' own Shopping campaigns. For example, Producthero offers an interesting tool for advertisers who wish to achieve additional visibility through feed optimisation. With our SEO for Shopping Ads tool you are able to enrich your own feed based on our data. Thus, strengthen your private campaigns.

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Joining Producthero CSS is quick and fully online. We only need your Merchant Center ID.

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Steps:

- Sign up at producthero.com/google-css‍

- We submit the switch request to Google (within 48 hours).

- Your Merchant Center will be fully converted to Productero CSS in less than a week.

Joining Producthero CSS costs just €39 per month and, if you want to expand to additional markets, each extra country or webshop costs only €19 per month.

There are no hidden fees: you only pay for the countries or webshops you choose.

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Yes. Agencies pay only €19/month per additional customer instead of the standard €39 monthly fee the customer would pay if they signed up directly. This gives you a margin of up to 51% for each customer you connect.

We do not need full access to your accounts. Having access to your Merchant Center helps us provide better service, but we cannot see campaign details.

You only need to give us access to your Google Ads account if you want support with your campaigns, but this is not a requirement.

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The price - We are very affordable. Our plans start at €39/month, and being competitively priced does not mean that only smaller webshops choose us. Well-known brands such as Ikea, La Redoute, MediaMarkt, Heineken, and O’Neill are advertising via Producthero.

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A high-quality comparison site - Our site attracts a good number of visitors every day. We’ve noticed that some CSS partners display ads on sites where you wouldn’t want your products at the bottom. Producthero is committed to a visible, trustworthy comparison site where real comparisons are made (something Google values). Unlike small, private CSS sites created just to exploit the CSS Program, with Producthero you benefit from a performance-based, well-functioning comparator.

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100% independent - Many CSS partners come from marketing agencies. As a webshop, you may not want to join an agency’s platform, and as an agency, you wouldn’t want to link your campaigns to a competitor. Producthero is fully independent, which is why many agencies choose us.

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We've arranged everything properly - Google account managers continue to provide support for your accounts. With Producthero, your Shopping ads appear everywhere Google Shopping runs, including the partner network and the Google Shopping tab.

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No CPC model - Google requires all products to stay on the CSS partner’s site. If a comparison site uses a CPC model, you would have to remove your products from it. Many webshops we work with have had problems with this.

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Perfect service - Our CSS and Shopping specialists are happy to assist you with any questions. We are a Premium CSS partner, so we also receive extensive support from Google to provide the best service to our customers.

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There is no notice period. You can cancel anytime, and we will handle the Merchant Center conversion and stop your subscription.