Performance Max (PMax) is Google's most automated campaign type. Give it a budget and some assets, and it will run ads across Search, Shopping, Display, YouTube, Gmail, and Google Maps, all from a single campaign. That sounds efficient, and when it works it can be. But Shopify merchants who launch PMax without proper setup routinely find it spending most of their budget on low-intent branded searches and Display placements that never convert.

Understanding what PMax actually needs from you is the key to making it work.

What Is Performance Max and How Does It Use Your Data?

Performance Max replaces Smart Shopping campaigns. It is a goal-based campaign that uses Google's machine learning to find conversions across all of Google's channels simultaneously. Rather than you choosing placements, targeting, and bidding manually, you tell it your conversion goal and give it creative assets. Google decides where, when, and to whom to show your ads.

PMax runs on your data. Specifically, it uses:

Your product feed from Google Merchant Center (for Shopping-style ads)
Your asset groups (headlines, descriptions, images, videos, logos)
Audience signals (customer lists and custom audience segments you provide as hints)
Conversion history from your account (purchase events from your Google Ads tag)
First-party data signals from your site (via your conversion tag and linked GA4)

The algorithm uses all of this to predict which users are most likely to convert and where to reach them. In the early weeks of a campaign, it is testing broadly. After accumulating enough conversion data (typically 30 to 50 purchases), it begins to optimise more accurately.

How Do Asset Groups and Creative Requirements Work?

An asset group is the container for your creative within PMax. One campaign can have multiple asset groups, each targeting a different product category or audience theme.

Each asset group requires:

Asset Type	Minimum Required	Recommended
Headlines	3	5+
Long headlines	1	3+
Descriptions	2	4+
Images (landscape 1.91:1)	1	3 to 5
Images (square 1:1)	1	3 to 5
Logo	1	2
Video	0 (auto-generated if missing)	1 to 3

The video requirement is technically optional, but if you do not provide one, Google auto-generates a video from your other assets. These auto-generated videos are almost universally poor quality and will run on YouTube. Always provide at least one video asset, even a simple 15-second product walkthrough filmed on a phone.

Write your headlines and descriptions to address different stages of intent: product-focused ("Organic Dog Treats, Made in the UK"), benefit-focused ("Free Next-Day Delivery on Orders Over £30"), and trust-focused ("Over 10,000 Reviews, 4.9 Stars"). Google mixes and matches these, so each one needs to stand alone.

Why Is Product Feed Quality the Foundation of PMax?

For Shopify stores with physical products, the Shopping component of PMax is typically where most of your budget is spent and where most conversions come from. The quality of your Google Merchant Center product feed directly determines how well PMax can serve Shopping ads.

Poor feed quality shows up as: low product visibility, ads showing for irrelevant searches, high CPCs, and poor ROAS. Strong feed quality looks like: ads appearing for the right searches, lower CPCs, and higher conversion rates.

Optimise your feed with these priorities:

Product titles: Include the most important keyword naturally. Format: Brand + Product Type + Key Attribute. For example: "Rosewood Leather Dog Lead, 120cm, Brown" rather than "Lead B00123".
Product descriptions: 150 to 300 words. Include materials, dimensions, intended use, and key differentiators. Not just a product teaser.
Images: Minimum 800 x 800 pixels. Clean background preferred for apparel and accessories. Lifestyle images can work for furniture and home goods.
GTINs: Include EAN or UPC where available. Products without GTINs have lower visibility in Shopping.
Price accuracy: Prices in your feed must match your Shopify store exactly. Mismatches trigger Merchant Center disapprovals.

Use Google's Merchant Center Diagnostics to identify disapproved products and fix them before running PMax.

When Does Performance Max Work Well, and When Does It Not?

PMax works well when:

Your Google Ads account already has a meaningful conversion history (30 or more purchases per month). The algorithm optimises on past data. Without data, it is guessing.
Your product feed is fully optimised and has fewer than 5 per cent disapproved products.
You have a clear product catalogue with strong images and descriptions.
You can provide audience signals from your own customer lists.
Your average order value is above £30. Very low-priced products struggle to generate profitable ROAS given typical CPCs.

PMax works poorly when:

Your account is brand new with no conversion history. Start with standard Shopping to build data.
You have a small catalogue (fewer than 10 products). PMax has limited product variation to test with.
Your feed has quality issues. PMax amplifies whatever is in your feed, good or bad.
You have a very narrow niche with low search volume. PMax will push budget to Display and YouTube where your audience is less qualified.

Should You Supplement PMax with Standard Search Campaigns?

Yes. One of the most common mistakes with Performance Max is treating it as a complete paid search strategy. It is not.

PMax does not give you control over branded keywords. It will capture some branded search traffic, but you cannot see or manage which branded queries are consuming budget. Running a separate branded Search campaign alongside PMax lets you capture your own brand name searches efficiently (branded keywords typically have ROAS above 8x) and prevents PMax from overinvesting in them at inflated costs.

Also run a non-branded Search campaign for your highest-value keywords. Standard Search campaigns let you control exact match keywords, write specific ad copy for specific intents, and send traffic to precise landing pages. PMax cannot do this with the same level of control.

A typical structure that works for UK Shopify merchants:

Performance Max (main product catalogue): 50 to 60 per cent of Google Ads budget
Branded Search campaign: 15 to 20 per cent of budget
Non-branded Search (top product keywords): 20 to 30 per cent of budget

How Do You Read Performance Max Reports?

Reporting in PMax is limited by design. Google deliberately restricts the visibility of where budget is being spent to prevent over-optimisation that would undermine the algorithm.

What you can see:

Asset group performance (top, good, low ratings for individual headlines, images, descriptions)
Audience insights (demographics and interests of converters)
Product performance (which products in your feed are converting and at what cost)
Search terms report (partial, available under Insights for Shopping activity)

What you cannot see directly: a full breakdown of spend by channel (Search vs Display vs YouTube), individual keyword-level data, or placement-specific performance.

To infer channel performance, look at impression share and average CPC over time. If your CPCs are very low (under 20p), budget is likely going to Display. If CPCs are in the 50p to £2 range for a typical ecommerce niche, budget is probably hitting Shopping and Search.

Use the Insights tab in PMax to review audience segments Google is targeting. If it is spending heavily on demographics that do not match your customer profile, add exclusions or adjust audience signals.

Key Actions to Take Now

Audit your Google Merchant Center product feed for disapproved products and fix title, image, and GTIN issues before launching PMax.
Create at least five headlines, three descriptions, five images, and one video for each asset group. Do not let Google auto-generate your video.
Upload your Shopify customer list to Google Ads as a Customer Match audience and attach it to your PMax campaign as an audience signal.
Run a separate branded Search campaign alongside PMax to control brand keyword spend independently.
Check the Insights tab in your PMax campaign weekly for the first month to see which audiences and product groups are receiving spend.
After 60 days, review product-level performance and consider excluding low-converting products from PMax using product group segmentation.
If your account has fewer than 30 monthly purchases, start with standard Shopping instead of PMax and migrate once you have sufficient conversion history.

Frequently Asked Questions

Can I run Performance Max and standard Shopping campaigns at the same time? Yes, but PMax will typically take priority over standard Shopping when they overlap on the same products. Many merchants run PMax for their main catalogue and use standard Shopping for new product launches or specific product groups where they want more manual control.

Why is my Performance Max spending mostly on Display and YouTube? This usually happens when your product feed has quality issues or when your campaign has insufficient conversion data. PMax defaults to broader channels when it cannot identify high-intent Shopping queries. Improve your feed, add audience signals, and give the campaign more time to accumulate purchase data.

How long should I run Performance Max before evaluating it? Minimum six weeks before drawing conclusions. The algorithm has a learning period of two to four weeks, and you need enough conversion data after that to compare ROAS meaningfully. Avoid making large budget changes during the learning phase.

Should I use a Target ROAS bid strategy in Performance Max? Once your campaign has accumulated at least 30 purchases, set a Target ROAS that is achievable based on your current account performance. Setting an aggressive Target ROAS too early causes the algorithm to restrict spend too tightly and prevents it from exploring new opportunities.

Shopify and Performance Max: How to Get Google's Smartest Campaign Working for You