What Is a Google Comparison Shopping Service (CSS)?

A Google Comparison Shopping Service (CSS) is a platform that allows consumers to compare products and prices from multiple online retailers and then click through to purchase directly from the merchant offering the best deal.

CSSs operate within the Google Shopping ecosystem and submit product listings to Google on behalf of merchants. These listings appear as Google Shopping Ads, clearly labelled with the name of the CSS provider (for example, “By Kelkoo” or “By Google Shopping”).

Why Comparison Shopping Services Exist

Comparison Shopping Services became prominent after the 2017 European Commission antitrust ruling, which found that Google unfairly favored its own shopping service over competitors. As a result, Google was required to:

• Treat its own shopping service as a CSS, not a privileged product
• Allow independent CSS providers to compete on equal footing
• Enable merchants to advertise through any approved CSS, not just Google Shopping

This change created a competitive ecosystem of CSS providers across the EEA and the UK.

How a Google CSS Works

1. Merchants submit product data to a CSS (instead of directly using Google Shopping as the CSS)
2. The CSS uploads products to Google Shopping
3. Ads appear across Google Search, Shopping, and Display placements
4. Shoppers click the ad and are sent directly to the merchant’s website
5. The CSS manages or facilitates bidding, optimisation, and feed compliance

Benefits of Using a CSS

For merchants advertising in the UK or EEA, using a CSS can offer:

• Lower cost-per-click (CPC) (often 15–20% lower)
• Improved auction competitiveness
• Access to expert feed and campaign optimisation
• Greater control over Shopping ad performance
• Reduced reliance on Google’s own CSS

Where CSS Is Relevant

• Highly relevant: UK and European Economic Area (EEA)
• Limited relevance: Outside Europe, where Google Shopping dominates without CSS competition

Prioritised List of Major Comparison Shopping Services (CSS)

Below is a priority based list of the most important and widely used CSS providers, grouped by market impact, coverage, and advertiser adoption.

Tier 1 – Highest Priority (Global / Market-Leading)

These CSSs have broad coverage, strong Google Shopping integration, and widespread advertiser use.

1. Google Shopping (Google’s own CSS)
   • Default CSS if no third-party is selected
   • Strong reach, no CPC discount advantage
   • Often replaced by third-party CSS for cost savings
2. Kelkoo
   • One of Europe’s largest CSS providers
   • Strong presence in UK, France, Germany, Spain
   • Popular with large retailers and agencies
3. Idealo
   • Market leader in Germany and strong across Europe
   • High-intent traffic
   • Often combined with Shopping ad services
4. PriceRunner
   • Strong in UK and Nordic markets
   • Trusted consumer brand
   • Good performance for electronics and home products

Tier 2 – Strong Regional & Specialist CSSs

Well-established CSSs with regional dominance or vertical specialisation.

5. ShopMania
   • Active across multiple EU countries
   • Competitive CPC structures
6. Twenga
   • Strong in France and Southern Europe
   • Suitable for mid-size retailers
7. Vergelijk.nl
   • Leading CSS in the Netherlands
   • Strong local consumer trust
8. LeGuide
   • Established European comparison platform
   • Often used for cross-border selling

Tier 3 – Niche, Local & Performance-Focused CSSs

Smaller or specialist CSS providers, often chosen for lower fees, niche markets, or agency partnerships.

9. Shopping24
   • Focus on German-speaking markets
10. PriceSpy

• Strong in Nordics and tech categories

11. Foundem

• Early CSS competitor
• Smaller scale but compliant with Google CSS framework

12. Local / Agency-Owned CSSs

• White-label CSSs run by PPC agencies
• Often used to pass CPC savings directly to advertisers

Important Note on “All CSSs”

Google does not publish a single public master list of every approved CSS.
There are dozens of smaller or private CSSs, including:

• Agency-owned CSS accounts
• Country-specific comparison engines
• White-label CSS solutions

The list above covers the most commercially relevant CSSs used by advertisers in the UK and EEA.

A Google Comparison Shopping Service is a powerful alternative to Google’s default Shopping setup, offering lower advertising costs and greater flexibility for merchants in Europe.

Choosing the right CSS depends on:

• Market (UK, EU, specific country)
• Product category
• Advertising budget
• Level of support needed (feed, bidding, optimisation)