If you advertise on Google Shopping in Europe, there is a good chance you are overpaying for every click. Google's own Comparison Shopping Service (CSS) quietly takes a ~20% margin from your bids before they enter the auction. Switching to a third-party CSS partner removes that margin—and it takes less than a day.
This guide explains what CSS partners are, how the 20% advantage works, the benefits and risks, and compares the major providers so you can make an informed decision.
What Is a CSS Partner?
In 2017, the European Commission fined Google €2.42 billion for abusing its dominant position by favoring its own Google Shopping service over competing comparison shopping sites. As a remedy, Google was required to open up its Shopping Ads platform to third-party Comparison Shopping Services on equal terms.
A Comparison Shopping Service (CSS) is a website that gathers product listings from online retailers and allows consumers to search, compare prices, and compare selling conditions. Under the restructured model, Google created Google Shopping Europe (GSE) as a legally separate entity that competes on the same terms as every other CSS.
Here is how it works in practice:
- You share your product data with a CSS partner (or they associate with your existing Merchant Center account)
- The CSS submits your product inventory to Google's Shopping auction
- When a shopper clicks your ad, they land directly on your website—not the CSS partner's site
- The ad displays a small "By [CSS name]" label at the bottom instead of "By Google"
The CSS program is available in 21 countries: the EEA member states, the United Kingdom, and Switzerland. It is not available in the US, Canada, Australia, or any non-European market.
The 20% CPC Advantage Explained
This is the core financial reason to consider a CSS partner. The European Commission requires Google Shopping Europe to be independently profitable, so Google deducts a fixed margin of approximately 20% from each merchant's bid before entering it into the auction. Third-party CSS partners do not take this margin.
| Scenario | Google's CSS | Third-Party CSS |
|---|---|---|
| Your bid | €1.00 | €1.00 |
| Google's margin | -€0.20 | €0.00 |
| Effective auction bid | €0.80 | €1.00 |
| Bidding power | Baseline | +25% more |
After switching, you have two strategies available:
- Keep the same bids to increase volume: Your ads become more competitive, winning more auctions and generating more clicks and impression share for the same budget
- Lower bids to improve profitability: Achieve the same ad positions as before but at roughly 20% lower CPC, improving your ROAS
Pro Tip
The discount is relative to competitors still using Google's CSS. If every competitor in your market has also switched to a CSS partner, the advantage neutralizes because everyone's bids are on equal footing. Early adopters in less competitive niches benefit the most.
Smart Bidding & Performance Max
The CPC advantage applies to both Standard Shopping and Performance Max campaigns. When you switch CSS, automated bidding algorithms (tROAS, tCPA, pMax) benefit from the increased bidding power, but they need 1–2 days to recalibrate. Expect minor performance fluctuations during this learning period as the algorithm experiments with bids to find the new optimum.
Benefits of Using a CSS Partner
- Up to 20% lower CPCs (or 25% more bidding power for the same spend)—the core financial advantage from removing Google's margin
- No disruption to existing campaigns: Your Shopping and Performance Max campaigns keep running without downtime when you switch
- Feed optimization services: Many CSS partners offer product feed auditing, attribute tuning, and title optimization as part of their package
- Additional reporting and insights: Some partners provide competitive intelligence, category benchmarks, and price competitiveness data beyond what Google offers natively
- Multi-CSS strategy: You can work with multiple CSS partners simultaneously for broader coverage. Google ensures you never bid against yourself across CSSs
- Organic traffic from CSS platforms: Many CSS partners operate high-traffic comparison websites (Kelkoo, Idealo, PriceRunner) that provide additional organic visibility for your products
- Works with all campaign types: The advantage applies to Standard Shopping, Performance Max, and free product listings
Drawbacks and Risks
- The "discount" is invisible: You will not see a line item in Google Ads showing savings. It manifests only as improved auction competitiveness, making it hard to measure directly
- Partner fees eat into savings: CSS partners charge fees (flat monthly, CPC-based, or commission on sales) that must be weighed against the bidding advantage
- Feed management conflicts: When multiple CSS partners touch the same product feed, it can cause attribute drift, disapprovals, and data inconsistencies
- Sub-account detachment risk: If your Merchant Center account is a sub-account under a Multi-Client Account (MCA), switching CSS detaches it from the parent. Shared settings must be reconfigured independently
- CSS Product Detail Pages (post-DMA): Since March 2024, CSSs can direct traffic to their own product pages, which may show competitor listings alongside your products
- Smart Bidding recalibration: Expect 1–2 days of performance fluctuation as automated bidding strategies adapt to the new auction dynamics
- Advantage can neutralize: If all competitors in your market also use CSS partners, you are paying CSS fees for parity rather than advantage
Important
Before switching, verify your new CSS partner has opted in for free product listings and "Shopping Ads beyond general search." Otherwise, you may temporarily lose organic Shopping visibility during the transition.
How to Switch to a CSS Partner
Switching from Google's CSS (instant)
- Choose your CSS partner using Google's official partner directory
- Provide your Merchant Center account ID to the partner
- The CSS partner initiates the switch through their CSS Center interface
- Approve the request in your Merchant Center under Settings > General account options
- The switch completes immediately—no waiting period when moving from Google's CSS
Switching between third-party CSSs (up to 14 days)
When switching from one third-party CSS to another, there is a grace period of up to 14 days during which you can revert. After the grace period, the switch completes and your old CSS is unlinked.
Full switch vs. association
CSS partners offer two integration methods:
- Full switch: Your Merchant Center account is fully integrated into the CSS partner's Multi-Client Merchant Center. Tighter integration, but more dependence on the partner
- Association: Your account is simply linked to the CSS partner. Settings remain unchanged, minimal effort, and you retain more independence
Key Takeaway
Your Google Ads account is completely unaffected by a CSS switch. The change happens at the Merchant Center level only. Campaign history, quality scores, and all optimization data carry over. There is no need to rebuild anything on the advertising side.
CSS Partner Providers Compared
There are over 1,000 registered CSS partners in Europe, but quality and services vary significantly. Here are the major providers:
| Provider | Pricing Model | Coverage | Key Strength |
|---|---|---|---|
| Producthero (Channable) | Fixed monthly | All 21 countries | Largest Premium CSS; 15k+ merchants |
| Kelkoo Group | CPC-based | 41 countries | 20+ years; top impression share |
| Redbrain | Commission (CPS) | All 21 countries | Pay only for sales; £1B+ driven |
| Connexity | Cost-of-sale | Multiple EU | Managed campaigns |
| Klarna | Varies | Multiple EU | Premium CSS + payment ecosystem |
| Shoptimised | Managed/unmanaged | UK-focused | Premium; strong UK expertise |
| Bidnamic | Free CSS tier | Multiple EU | AI bid management included |
| shopping24 (mrge) | Fixed price | DACH + EU | No commission; 100% bid to auction |
| Idealo | Varies | Germany | Major comparison site traffic |
| PriceRunner | Varies | Nordics | Strong Scandinavian presence |
You can browse the full list on Google's official CSS partner directory or CompareCSS.com. When choosing a provider, consider your primary market, preferred pricing model (flat fee vs. performance-based), and whether you need managed services or just the CSS association.
CSS Partners After the Digital Markets Act (2024)
The EU's Digital Markets Act (DMA) designated Google as a "gatekeeper" platform, with compliance required by March 6, 2024. This brought significant changes to the CSS landscape:
- CSSs can now bid directly in auctions with their own Product Detail Pages (PDPs), not just on behalf of merchants
- New "Products" and "Product Sites" tabs replaced the old Shopping tab in Google search results
- Increased auction competition: CSS PDPs competing alongside merchant PLAs can inflate CPCs
The ecosystem has grown substantially. By end of 2024, there were over 1,000 registered CSS partners, serving 600,000+ merchants, and generating 19 billion clicks on third-party CSS ads—a 92% increase from 2021.
Looking ahead to 2026, stricter feed compliance requirements are being rolled out. Non-compliance risks disapproved listings, higher ad costs, and lost visibility across EU markets. Keeping your Google Shopping feed in top shape is more important than ever.
Frequently Asked Questions
Can I use CSS partners outside Europe?
No. The CSS program is available only in 21 countries: the European Economic Area (EEA), the United Kingdom, and Switzerland. It does not exist in the United States, Canada, Australia, or any other non-European market.
Do I lose my campaign history when switching CSS?
No. Your Google Ads account is unaffected by a CSS switch. Quality scores, campaign history, and optimization data all carry over. The change happens at the Merchant Center level only.
Can I use multiple CSS partners at once?
Yes. You can operate multiple Merchant Center accounts, each under a different CSS, for the same website. Google ensures you never bid against yourself across CSSs, so using multiple partners is safe.
Does CSS work with Performance Max campaigns?
Yes. The CPC advantage from using a CSS partner applies to all Shopping placements, including those served through Performance Max campaigns. Smart Bidding algorithms may need 1–2 days to recalibrate after a CSS switch.
How much do CSS partners charge?
Pricing models vary widely. Some offer free tiers, others charge a flat monthly fee (typically €50–500), while performance-based partners charge a percentage of ad spend or commission on sales (5–15%). The cost must be weighed against the ~20% bidding advantage.
Will Google penalize me for leaving their CSS?
No. All CSSs compete on equal terms in the Shopping ad auction. No ad space is reserved for Google Shopping or any other CSS. Google is required by the European Commission to treat all CSSs equally.
Conclusion
CSS partners offer a real but nuanced financial advantage for European merchants advertising on Google Shopping. The ~20% bidding advantage is genuine, but it must be weighed against partner fees, operational complexity, and the diminishing returns as more competitors adopt CSS partners themselves.
The right CSS partner for you depends on your market, budget, and how hands-on you want to be. Fixed-fee partners work well if you want a simple, predictable cost. Commission-based partners reduce risk since you only pay when you sell. And if you are already managing complex Shopping campaigns across multiple countries, a premium partner with feed optimization and reporting tools will likely pay for itself.
Whatever CSS setup you choose, the most important thing is tracking how the change affects your actual Shopping performance. Use SKU Analyzer to monitor product-level metrics, wasted spend, and ROAS shifts before and after the switch so you can measure real impact rather than relying on theoretical savings.