Google Ads for E-commerce: Complete Guide to Shopping & Performance Max 2026

If you run a webshop and advertise on Google, there are two campaign types you need to master: Google Shopping and Performance Max. Together they can account for 60–80% of all paid traffic — and for many webshops they are by far the most important channel for profitable growth.

The problem is that most webshops either run them incorrectly, skip essential steps, or hand everything over to Google's autopilot without understanding what is happening under the hood. That costs money.

This guide gives you the complete playbook: what the two campaign types are, when to use which, how to optimize your product feed, and which mistakes destroy results for the majority of webshops. We are a Google Ads agency in Aarhus with experience ranging from niche webshops to large e-commerce brands — everything below is based on real campaigns and data from 2026.

1. Google Shopping Ads

What are Shopping ads?

Shopping ads are the product cards you see at the top of Google's search results — with a product image, title, price, and store name. Unlike text ads, they show potential customers exactly what they are buying, at what price, before they even click. This creates high purchase intent and better conversion rates than most other ad formats.

Technically, Shopping ads work differently from Search: you do not bid on specific keywords. Instead, Google matches your products to relevant searches based on data from your product feed. The feed is the foundation for everything — which is precisely why feed optimization is the most important lever in your Shopping setup.

Product feed: the technical foundation

The product feed is a structured data file containing all information about your products — and it is uploaded to Google Merchant Center, which is free to create. Merchant Center is the bridge between your webshop and your Google Ads campaigns. No Merchant Center, no Shopping ads. It is that simple.

The feed must contain at minimum these fields for each product:

• id — unique product ID
• title — product title (max. 150 characters)
• description — product description (max. 5,000 characters)
• link — URL to the product page
• image_link — URL to the product image (min. 100 × 100 px)
• price — price including VAT
• availability — in stock / out of stock
• google_product_category — Google's product taxonomy code
• brand — brand name
• gtin or mpn — product identifier (EAN/barcode or model number)

Most e-commerce platforms (Shopify, WooCommerce, Magento) can generate the feed automatically via plugins. But automatically generated feeds are rarely optimized — they simply use your product data as-is, and that is far from what Google rewards.

Bid strategies for Shopping

Google Shopping primarily supports two Smart Bidding strategies suited to webshops:

Target ROAS (tROAS): You specify a target Return on Ad Spend, and Google's algorithm adjusts bids to reach that target. Requires a minimum of 15–20 conversions per month to function properly. Good for stable campaigns with sufficient data.

Maximize Conversion Value: Google automatically bids to maximize total conversion value within your budget. Easier to get started with since it does not require a specific target. The transition to tROAS happens naturally once you have enough data.

The CSS Partner advantage: up to 20% lower click prices

Here is a competitive edge most webshops do not know about. Google's CSS program (Comparison Shopping Service) is an EU-regulated scheme that gives your webshop up to 20% lower click prices on Shopping ads, without any change to your ad position, visibility, or campaign setup.

The principle is simple: instead of advertising directly through Google's own Shopping system, you advertise through an approved CSS partner. Google provides this discount because the EU has required them to treat third-party CSS providers on equal terms with their own system. Gezar is an approved CSS Partner, so all our webshop clients automatically receive this discount.

For a webshop spending DKK 30,000/month on Shopping, the CSS discount can save up to DKK 6,000 per month — that is DKK 72,000 per year that you can reinvest in more traffic or better margins.

2. Performance Max (PMax)

What is PMax?

Performance Max is Google's most ambitious — and most debated — campaign type. Instead of you choosing channels and keywords, PMax uses Google's machine learning to show your ads where the algorithm expects the highest conversion value. It covers all of Google's channels at once: Search, Shopping, Display, YouTube, Gmail, and Maps.

You supply the raw materials — images, copy, videos, and audience signals — and Google assembles and tests combinations automatically. It sounds appealing, but PMax is not an autopilot you simply switch on and forget. The quality of your input largely determines the quality of the output.

Asset groups: the creative foundation

In PMax, everything is organized into asset groups — collections of creative material used to build ads across the channels. An asset group can contain:

• Images: Minimum 1 landscape (1.91:1), 1 square (1:1), 1 logo. The more variants you provide, the better Google can optimize.
• Copy: Up to 5 headlines (30 characters), 5 long headlines (90 characters), 5 descriptions (90 characters). Write varied versions — not just repetitions.
• Videos: Not mandatory, but strongly recommended. Without video, Google automatically generates videos from your images — and they are rarely attractive.

Segment your asset groups logically: one group per product category or per audience. This gives you better insight into what works and gives Google better data for optimization.

Audience signals: help the algorithm get started

One of the most important — and most often overlooked — parts of PMax is audience signals. You cannot force PMax to only show ads to specific audiences (this is not traditional targeting), but you can tell Google which users are likely to convert. This gives the algorithm a solid starting point rather than having to learn from scratch.

Use these audience signals:

• Remarketing lists: Visitors to product pages, existing customers, cart abandoners. The strongest signal you can provide.
• Customer Match: Upload your existing customer list. Google automatically finds similar users (similar audiences).
• Custom segments: Define segments based on keywords (people who have searched for specific terms) or URL visits (people who visit competitor webshops).
• In-market audiences: Google's own segments of users with active purchase intent in your category.

POAS tracking with PMax

PMax is designed to optimize toward conversion value — but by default conversion value is your sales price, not your profit. If you use standard ROAS tracking, the algorithm blindly bids on high-revenue products while ignoring whether they are actually profitable.

With POAS tracking (Profit on Ad Spend) you instead send your actual contribution margin to Google as the conversion value. PMax then optimizes toward real profit — and that changes bidding dramatically. High-margin products are prioritized, low-margin products are scaled back. The result is a better bottom line without necessarily increasing the budget.

3. Shopping vs. PMax: When to Use Which?

This is not an either/or choice. Most mature webshops run both campaign types in parallel. But there are situations where one is clearly better than the other.

The recommendation is clear: Start with standard Shopping. It is simpler, gives more control, and works with a lower budget. Add PMax campaigns after 30–60 days, once you have conversion data and a well-optimized feed. Run both in parallel with approximately 60% of budget to Shopping and 40% to PMax.

4. Feed Optimization: The Most Important Thing You Can Do

If you have control over one element in your Shopping strategy, it should be the product feed. A poor feed destroys even the best campaign structure — and a good feed lifts results across everything.

Product titles: keyword-rich and precise

The product title is the most important factor for which searches your products match. Google actively uses the title to determine relevance. Write titles that contain the most relevant keywords — imagine what your customer is searching for and build the title systematically:

Format: [Brand] + [Product type] + [Key specification] + [Variant/Size/Color]

Example: "Nike Air Max 90 — Men's Trainers — White — Size UK 9" is far better than just "Air Max White" or your internal product code.

You have 150 characters available — use them. The most important keywords should appear first, as Google truncates long titles in the display.

Product descriptions

Descriptions are rarely shown in the actual ad display, but Google indexes them and uses them to determine relevance for more specific searches. Write 500–1,000 characters with natural language that includes relevant keywords, specifications, and use cases. Do not simply copy your website's description blindly — optimize it for search relevance.

Google Product Taxonomy

Correct categorization via Google's product taxonomy helps the algorithm understand your product and show it to the right searches. Use the most specific category that applies — not just the top level. "Apparel & Accessories > Clothing > Outerwear > Coats & Jackets" is far better than just "Apparel & Accessories".

Image quality

Shopping is visual. A professional product image on a white or neutral background converts significantly better than a poor image. Google has technical minimum requirements (min. 100 × 100 px, max. 64 MB), but in practice you should use images of at least 800 × 800 px. Lifestyle images can be used as supplementary images, but the main image should always show the product clearly and prominently.

Custom labels: segment your products

Custom labels are your own classifications on top of Google's standard structure. You have 5 custom label fields available (0–4), and you define what they mean. Use them to segment campaigns more intelligently:

• Label 0: Margin category (high, medium, low) — for POAS optimization
• Label 1: Seasonality (summer, winter, evergreen)
• Label 2: Bestseller / new / sale
• Label 3: Stock status or reorder time
• Label 4: Price bracket (under DKK 200, DKK 200–500, over DKK 500)

Custom labels let you bid differently on high-margin vs. low-margin products, seasonal vs. evergreen products, and new releases vs. established bestsellers.

5. Budget Tips for Webshops

Budget is one of the most frequently asked questions — and one of the hardest to answer without knowing your specific situation. But here are the general guidelines we use with our webshop clients:

1. Minimum: DKK 5,000–10,000/month in ad spend Below DKK 5,000/month it is difficult to generate enough conversion data for the algorithms to optimize meaningfully. You will see traffic and perhaps sales, but you will wait a long time for the data you need to scale. DKK 5,000–10,000 is the realistic minimum threshold to get started properly.
2. Start with Shopping, add PMax after 30 days The first 30 days are the data collection phase. Run standard Shopping with Maximize Conversion Value. Use the data to optimize the feed and identify which products and categories perform. Add PMax in month 2 with strong audience signals based on the data you now have.
3. Split: 60% Shopping / 40% PMax This split works well for most webshops in the growth phase. Shopping gives control and transparency, PMax scales across channels. Adjust the split based on ROAS/POAS data from the first 60–90 days.
4. Peak season: increase budget 2–4 weeks in advance PMax has a learning period. If you dramatically increase your budget on Black Friday itself, it is too late — the algorithm is not ready. Plan budget increases 2–4 weeks in advance so the algorithm has time to adapt to the new budget level.

Remember these figures are ad spend — the amount you pay to Google. Agency fees come on top. A rule of thumb: agency fees should not exceed 20–25% of your total ad spend. If they do, you should be asking questions.

6. 3 Mistakes Most Webshops Make

We see the same mistakes again and again. The three below account for the majority of wasted ad spend across the webshops we audit.

• 1
  Poor product feed This is the most widespread mistake and the one with the greatest consequences. Webshops using auto-generated feeds without optimizing titles, descriptions, and categories pay significantly higher CPC and match the wrong searches. A product titled "Blue Jacket M-67" matches far fewer relevant searches than "Men's Winter Jacket Blue — Waterproof — Size M". The feed is your foundation — invest time in it.
• 2
  No negative keywords in Shopping Many believe negative keywords do not work in Shopping — that is wrong. You can add negative keywords to standard Shopping campaigns, and you should. Regularly analyze your search terms report in Merchant Center and Google Ads and exclude irrelevant terms. Selling new products? Add "used", "second hand", "review" as negatives. Selling premium? Add "cheap", "free", "download". This saves you clicks from people who would not have bought anyway.
• 3
  PMax without audience signals Starting a PMax campaign without audience signals is like onboarding a new employee with no introduction and letting them guess their way through the job. The algorithm has to learn from scratch, and that takes time — and money. Always upload your existing customer list, add remarketing lists (product page visitors, cart abandoners), and define custom segments based on keywords and competitor URLs. This gives the algorithm a far stronger starting point and significantly reduces the learning period.