The Ultimate Google Shopping CSS Guide: Best Practises from more than 400 Migrations


What is Google Shopping CSS?

Google Shopping CSS is a new form of advertising. CSS stands for Comparison Shopping Services and especially applies to ads that are displayed on the main search page (Google homepage).

As an advertiser, you can set up CSS to optimize your Google Shopping accounts. However, the whole thing does not work through common PPC optimization changes of campaign set-ups and settings in Google Ads, but also through the participation in a specific program on Google – the Google CSS Partner program. Advertisers have access to this program by working together with a certified Google CSS partner. We are such a Google CSS partner.

CSS applies to each advertiser that places ads through Google Shopping. Therefore, each advertiser should benefit from CSS at least in depth because its optimization potential is enormous: CPCs, which are reduced by about 20%, are resulted from placement of ads via a price comparison tool, so-called CSS, through the different compositions of the product bids in the auction for an ad rank.

You can see in detail below how your bids are currently structured in Google Shopping, and how your CPCs are changed by CSS.

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What does Google Shopping have to do with Comparison Shopping Service (CSS)?

Google CSS
Basically, we would all probably be in agreement that we see the Google search engine here. From the perspective of the European Commission, however, we see mainly many different product offers including a search engine and independent price comparison under the “Shopping” tab.

Google CSS: SEA

This search engine also enjoys a dominant position in the European market. The European Commission recognized an unfair treatment of its own price comparison offers and sentenced Google a record fine of EUR 2,42 billion in 2017 due to unfair competition.

Google Shopping

Illegal advantage for Google Shopping?

If you would like to learn more, you can find the entire case in the following link:

If we click on the “Shopping” tab on the search result page, according to the understanding of commission, we see a price comparison page, which has actually similar functionality as the classic comparison page:

Independent Price Comparison

Independent Price Comparison

As further penalties were pending, Google had to find a solution as quickly as possible to avoid extra penalties. Two things had to be done:

  1. Google had to prove that abuse of the dominant position had been eliminated so that, a fair competition was created in the search results.
  2. Also, Google had to show that its own price comparison platform (Google Shopping Europe (GSE)) is able to work independently on its own.

To manage equal opportunity, Google redesigned the advertising platform as a price comparison page and opened it for external price comparison platforms – so-called Google CSS Partners. The result: for some time now, all shopping ads which are displayed on the main search result page on Google are part of Google Comparison Shopping Services (CSS). Google also made it possible for other price comparison platforms to buy paid results on the search results page.

Google Shopping Europe (GSE) itself also functions as CSS (“by Google”), participates in the bidding auction like other price comparison platforms and competes with other CSSs that place bids on behalf of merchants. To use its own comparison shopping as EU agree (we remember: GSE must work profitable independently), Google’s observations show that it maintains about 20% of your maxCPC bid as a margin. Therefore, your bids are reduced by about 20%, if you leave it on Google Shopping Europe. On the other hand, if you use Google CSS Partner for your ads, the margin is completely deducted.

In conclusion, these efforts brought an external price comparison shopping back into the position of selling fair ad places on Google search. You can find more about the background of the introduction of Google Comparison Shopping Services in our blog post.

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What are the changes by Google Shopping CSS for Google Users?

The difference is hardly recognizable for Google users. Only the added line “by…” at the bottom of the ad is visibly new.

Google CSS with Adference


Let’s take a closer look at the search results page: The results above the text ads will be displayed through Google Shopping as usual. For each of these ads now you have a source reference (“by Google”, “by ADFERENCE”, etc.). This reference clearly shows you which CSS Partner the advertisers are currently cooperating with.

In general, the introduction of the source's reference was only the preparation for the further changes that would follow. If an advertiser buys your ad through a CSS partner on Google Shopping, then their names are displayed as the source below the ad. Nothing changes for the users when clicking on the advertisement. They will be forwarded directly to the offer of the advertisers who have booked the ad on Google.

The only tangible change for the user takes place when they click on the source below the ad:

In this respect, they are forwarded to a relevant price comparison page, by which the ads are controlled. For example, this could be Google, or it could be other price comparison pages like ours.

By the way: Google's image search was also included in Google’s main search network in 2019, i.e. shopping ads are now displayed there by default. Previously, advertisers could only target the image search using an opt-in in the extended Google Partner Network. Although the image search falls beyond Google’s own price comparison – to be found under the “Shopping” tab – no price comparison are shown on the image search page but rather standard shopping ads:

CSS White Jeans Ads

White Jeans Ads

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For whom is Google Shopping CSS? How can a Google CSS Partner help me as a retailer?

The changes concern each advertiser in Google Shopping and affect the performance – even though you did not make any changes: Your Shopping Ads are already displayed on Google’s own price comparison site Google Shopping Europe (GSE). The disadvantage: To use the price comparator Google Shopping Europe, Google deducts approximately 20% of your maxCPC bid as margin. As a result, your bids are reduced by the amount of the margin in the auctions for the ad places in the Google main search.

However, you can prevent the reduction of your CPCs, if you use a Google CSS Partner instead of Google Shopping Europe. In the following section you will learn how Google CSS is related to your CPCs:

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What does Google Shopping CSS actually change for the advertisers?

For you, as an advertiser, the structure of your Google Shopping bids, with which you enter the auction for the ad rank, changes after the migration from Google Shopping to CSS: Let’s say you start with maxCPC bid of 1€. If you still use GSE, 0,20 € margin is deducted from the bid. The result: you compete with the ad rank with the reduced bid of 0,80 €.

If you do not advertise on GSE, but rather on another Google CSS Partner, this margin drops. Your bids will be auctioned in full, i.e. with 1€. The advantage: You win more auctions with the same maxCPC bid and you can significantly increase your traffic.

Google_Shopping_CSS_MerchantGoogle Shopping CSS Merchant


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How can I become a Google CSS Partner?

Anyone who conducts a price comparison and creates a price comparison that meets the defined criteria can become a Google CSS Partner. If this is the case for you, you can directly activate your price comparison for the Google CSS Program on Google. However, our advantage is that we were already a big partner with Google since we started with the topic. So we can start fast and efficiently.

After the comparison is certified by Google for the first time, we have to be activated as a partner for every country we would like to offer services, which currently works in the form of self-certification. Here, the certain criteria are applied which must be fulfilled and which are regularly checked by Google.

On the following page, you can always find the current information about the Partner program.

Grow your business with Google CSS

Grow your business with Google CSS


Our Comparison Shopping: The ADFERENCE CSS

We perform price comparison not only conforms to the rules but it is also user-friendly and looks as follows:

ADF Shopping
If you are interested in ADFERENCE CSS, you can find here:

With this price comparison, we are certified for the majority of the European market, which means that we are allowed to target ads in almost all countries of the European Economic Community.


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How can I start with Google Shopping CSS? How does it work?

If you like to use Google Shopping CSS through a Google CSS Partner, the CSS Partner needs to submit an application for the activation of your Merchant Center Account (MCA). In fact, the process behind this is quite simple on Google: the CSS Partner submits predefined texts with your information directly to Google.

Predefined texts

Predefined texts

For the migration of your Merchant Center to your CSS Partner, you have basically two options:

  1. Full: Your Merchant Center account is fully integrated into the CSS partner’s MCA. As a result, your default Google Shopping setting will change for you as well as possible access permissions.
  2. Association: The account is linked to Google CSS. You maintain full control over the account. Your Google Shopping setting does not change anything for you.

If you have in mind advertising your Google Shopping Ads with ADFERENCE CSS: we advise you to decide on the Association. For you, there is more or less no migration effort – everything stays the same. You can immediately continue to work in your familiar settings without adjusting to new circumstances.

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Margin Advantages and SpendMatch: Is it worth to switch to a Google CSS Partner?

Everyone, who advertise Google Shopping Ads, should consider switching to Google Shopping CSS with the help of a CSS Partner. The Google CSS advantages result from the reduction of the margin of about 20%, which Google deducts from the shopping bids in the auction for the allocation of ad place if they are controlled through GSE.

If you switch to Google CSS, you prevent performance disadvantage by 20% lower CPCs.

The effort on your site is minimal, on the other hand, the advantages are enormous.

Meanwhile, Google also offered the merchants generous financial incentives to promote their products through external price comparison sites: Merchants in the “SpendMatch” received a bonus for their ad contributions. The bonus and the auction advantage offered huge savings opportunities by eliminating the margin. The “SpendMatch” program ended on December 31, 2018, but the biggest benefit – the auction benefit – remains.

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Comparison Listing Ads: CSS gets its own Google Shopping Ad Format

CSS has become almost an essential tool for many advertisers. The fact that CSS is now firmly established in Google Shopping and has reached a particular maturity since its introduction is proven by the launch of a new ad format – designed exclusively for Google CSS providers: Comparison Listing Ads (CLA), which were launched in March 2019 as a Beta version in Germany, France, and the Netherlands.

The comparison ads are separate ad formats, which are only available to the Google CSS Partners and provides extended range. They contain a second advertising carousel in addition to the standard shopping ads:

Comparison site css

Comparison site

The only requirement to use Comparison Listing Ads is that the Google CSS Partner must be invited to participate in the CLA program. As you can see in the Comparison Shopping Ad above, the ADFERENCE CSS is one of them.

If a Google user clicks on a price comparison, similar products are shown from the category. Therefore, it is crucial to maintain category labels in the product database.

If you are not working with a CSS Partner, you will definitely be missed out in the extended range. Without a Google CSS Partner, access is impossible: only price comparison portals can place the Comparison Shopping Ads in the name of the sellers.

Branding & More Visibility for Products in Price Comparison

A Google CSS Partner mainly books these ads for themselves: their price comparison gets more visibility and additional traffic, which in turn can benefit the merchants who offer their products in the price comparison. However, the merchants cannot place comparison listing ads by themselves – the ad format is only open to the Google CSS Partners.

Among other things, the comparison ads are intended to support the branding of the price competitors and to attract the users directly to the price comparison pages. It is yet to be clarified whether the ad format will be successful in this respect: Many price comparisons conducted by marketing agencies or tool providers do not have any interest in the branding of their own service.

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Google CSS Strategies & Best Practices for the Optimum Use of CSS

Anyone, who is thinking about switching to Google Shopping CSS, sooner or later asks themselves these questions:

  • What happens if I leave everything on GSE?
  • How should the account and campaign set-up look like after the migration?
  • Does it make sense to move all the accounts to the Google CSS Partner?
  • Or are there even advantages in targeting by dividing the accounts into GSE and CSS?

We will take a look at the options:

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1. Keep it up: You don’t change anything and stay with GSE

All your accounts and campaigns stay linked to the Merchant Center from Google Shopping Europe. Your ads will be played out like it used to. On the basis of margin, Google Shopping Europe increases your bids, so you can experience performance losses.

The display of the product ads does not change: if you leave your product ads with GSE, the link is named “By Google” and will direct you to ad results in the Google Shopping tab. If the shopping ads are advertised through a Google CSS Partner, the blue link under the ad changes into “By ADFERENCE Shopping”.



"By ADFERENCE Shopping"

You are automatically at a disadvantage because of margin: This strategy is not recommended under any circumstances.

If you decide for a Google CSS Partner like ADFERENCE, you are presented with the choice:

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2. GSE + CSS: The Double Strategy

In the Double Strategy, CSS advantages can be combined with those of GSE. You have many options to implement these:

  • Option 1: Switch the existing account including history and quality factor to Google CSS. Your new GSE account is set up with the same campaign, settings, and feed.
  • Option 2: The existing account stays with GSE. The newer Google CSS account will be linked through MCA.

From today’s point of view, it can be said that this strategy has developed over time. In the beginning, the 2-Account Strategy had to be shown in the Google main search results page, as well as under the “Shopping” tab. As mentioned previously, Google CSS is only available for the Google search, not for the Google Shopping tab – this Google Shopping tab is the price comparison page from Google. This is no longer necessary because an opt-in is provided for the display under the shopping tab.

With the Double Strategy, you have the possibility of generating traffic with various bids based on the placement (Google main search results page and Google Shopping tab & Partner Networks). Therefore, that would particularly be useful, because the traffic on Google Shopping tab and Partner Networks often performs much worse than Google main page.

  1. Normal/High Bids on the main page through CSS account
  2. Low bids on the Google Shopping tab & Partner Networks through GSE account
Double Strategy

Double Strategy

You can also use your different accounts to reach various positions. This strategy is exciting especially for big advertisers, who are not back away from increasing expenses.

Shopping Tab
Shopping Tab 


How is the Double Strategy evaluated?

A big drawback for the Double Account Strategy is that it folds maintenance effort in two, which results from the duplication of the accounts. Unfortunately, the expected performance gains fail to appear: using various bids for both search results page (Google main search page & shopping tab with Partner Networks) is only worthwhile if a great number of clicks is generated: However, typically the traffic share in shopping tab and Partner Networks is low.

Google tries categorically to eliminate the double serving of the ads: the same product or article id GTIN (Global Trade Identification Number is used) will no longer be displayed several times in the search results page. However, since ads for very similar products are provided in minor variants (ads for shoes in two different sizes, or the same notebooks with different storage capacity), the double serving gives you the possibility to pop up more often in the shopping placements, and therefore, to occupy more space in Google search.

On the other hand, if an online retailer has a few products with a small number of variations, the Double Account Strategy may not generate any significant increase in traffic or in the performance in most cases. This strategy is not recommended in this situation.

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3. Complete Migration to CSS

In the vast majority of cases, the complete migration with all accounts and Google Shopping campaigns to CSS works well:

Our recommendation: 1-Account Strategy: Both the benefits for the user and the campaign settings remain exactly as they were before the migration. In most cases, we find the best cost/benefit here: The cost goes against 0 – and that with full utilization of all CSS advantages.

Multi-Account Strategy: The Benefit of Several Google CSS Partners – It is a version of the complete migration, which is really exciting among the advertisers and has some basic similarities with “the Double Strategy”.

The multi-account strategy allows advertisers to run their shopping ads in parallel using multiple Google CSS Partners. The combination of different opt-ins – for or against the display of ads under the shopping tab– allows products, bids, and ad formats to be controlled in a parallel way.

Result: even though Google tries to prevent a retailer’s product from allocating several places in a search result, the use of several CSS by placing similar products seems to cause a higher allocation of shopping placements.

This strategy can generate very good results if it fits the retailer. Unfortunately, it cannot be scaled infinitely. With every additional CSS, a decreasing marginal return can be expected.

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How does Google CSS improve my performance?

Performance Improvement

Performance Improvement

The effects are huge. The case shows an example of the development of a real, and big account after the migration to Google CSS. In the graphic, we can see that the significant change in performance is observed after the migration. Generally, the number of impressions increases massively, while the price per click decreases at the same time. This effect is sometimes stronger and sometimes weaker, but it can be seen in almost all migrated Google CSS accounts without exception.

The longer the topic CSS is on the market, the fewer the impacts will be. First Mover advantages can no longer be generated by CSS. However, a major disadvantage compared to other advertisers who use CSS can be compensated. Therefore, this effect can be still seen today.


Almost without exception, the expected performance gains have been achieved from more than 400 supported migrations to Google Shopping CSS. There are a few arguments against CSS. If you decide to migrate to Google CSS, a Google CSS Partner can accompany you in a professional way.

In our following CSS FAQ, we have brought together the most frequent and important questions about switching to Google Shopping CSS.

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Frequently Asked Questions/FAQ

I would like to reduce the costs by low-cost CPC with Google Shopping CSS. Can I cut back the budget easily?

If you want to reduce the costs, it is a good idea to reduce the budget. However, reducing your daily budget must be your last step: if you want to get the same traffic with a low-cost CPC, you should start with narrowing the optimization targets or with a lower maxCPC bids. Important: after connecting to the CSS Partner, you should not start with a limited budget.

I would like to get more traffic with Google CSS. Which strategy should I follow?

After migrating from GSE to CSS, the margin reduced from your bids will drop. If you keep your CPC at this level, you enter the auctions with a higher maxCPC. The conclusion: your ads will be displayed more often and you will get more traffic. There is no need to make any changes, this happens automatically.

Everything for more sales: I would like to reinvest the savings from Google CSS directly.

If you would like to reinvest your savings to Google CSS by about 20% cheaper CPC, you should lower your optimization target or your maxCPC by 20%.

However, we advise not to increase the bids right after switching to CSS. This should be performed in 1 or 2 weeks at the earliest after the migration.

Who is my contact person after the migration?

Who will be your contact person for Google Shopping after the migration depends on whether your CSS agreed on the so-called “waiver”. The waiver gives your Google Account Manager access to your accounts after the migration. In this case, they can also assist you.

You want to get started with CSS? Contact us now!



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