Customer Match: Using Your Own Customer Lists in Google Ads

What Customer Match does

Google's About Customer Match page says it "lets you use your online and offline data to reach and re-engage with your customers across Search, the Shopping tab, Gmail, YouTube, and Display". You upload customer details, Google finds the ones that belong to Google accounts, and the result becomes an audience segment you can add to campaigns. Ads reach those people when they are signed in to their Google account. Google notes that third-party ad serving creatives are not supported with Customer Match.

Typical uses for a small business: telling existing customers about a new service or a loyalty scheme, raising bids on Search for people who already buy from you, or excluding current customers from a campaign meant to win new ones. Customer Match is one part of remarketing; our guide to remarketing audiences covers website visitor segments and Meta's custom audiences, and this guide goes deeper into the list itself.

Who can use it, and how

The Customer Match policy requires "A good history of policy compliance" and "A good payment history". What you can do with a list then depends on the account:

• All policy-compliant accounts can use Customer Match in the "Observation" setting and for exclusions.
• Accounts with 90 days of Google Ads history and more than USD $50,000 total lifetime spend can also use the "Targeting" setting and manual bid adjustments.

So a new or small account can still watch how listed customers behave (observation) and keep them out of prospecting campaigns (exclusion). Google also says it may remove access to Customer Match for any advertiser, for example after user feedback or repeated policy violations.

Which customer data you may upload

The policy allows only "customer information that you collected in the first-party context": data people shared directly with you on your website, in your app or in your store. Google's examples are a website purchase, an app sign-up for marketing messages and a loyalty programme sign-up in a physical store. A list you bought or rented does not qualify.

The same policy also requires you to:

• say in your privacy policy that you share customer data with third parties to perform services on your behalf;
• obtain consent for that sharing where the law or Google's policies require it;
• upload only through Google's approved API or interface;
• not upload information about anyone under 13, or collected from a site or app directed to children under 13.

Ads in a Customer Match campaign may not imply that you know personal or sensitive information about the viewer, and you may not combine a list with other targeting so that the ad reaches a very small group. Our website privacy basics guide covers the privacy policy side. If your list comes from a newsletter, the opt-in records described in our email marketing basics guide help show where each address came from.

Preparing the file

Google's page on creating a Customer Match list by uploading a data file sets the format. The main rules:

• File type. A CSV file encoded in ASCII or UTF-8; UTF-16 is not supported.
• Headers. Exact English column names: Email, Phone, First Name, Last Name, Country, Zip, User IP address and User interaction timestamp. Matching on a mailing address needs all four of First Name, Last Name, Country and Zip. Mobile Device ID goes in its own file as the only column.
• Email. Include the domain, remove spaces, and lowercase it if you hash it yourself.
• Phone. E.164 format with the country code, for example +12345678910. The plus sign is optional in plain text but required in hashed data.
• Names. No prefixes such as Mr. or suffixes such as Jr.; accents are allowed.
• Country and Zip. Never hashed. Use two-letter country codes and include the country even if every customer is in the same one. US zip codes may be five digits or five plus four.
• Timestamps. A timestamp alone, without an IP address or contact data, triggers an error.

You can upload plain text and let Google Ads hash it with SHA256, or hash it yourself. If you hash it yourself, Google asks you to normalise first: trim spaces, lowercase the text, format phones to E.164 and remove the dots before the domain in gmail.com and googlemail.com addresses, then use hex SHA256. Uploads through the API must be hashed. Google's troubleshooting page warns that a wrongly hashed file "may still be accepted" but will not match, which shows up as a small list. The same page links to a formatter tool to check your hashing.

How Google matches and handles the data

Google's article About the customer matching process explains that when you upload plain text, only the private fields (Email, Phone, First Name and Last Name) are hashed, and the upload travels over TLS. Google compares each hashed email or phone with the hashed details of Google accounts and adds matching accounts to your list. For mailing addresses it builds a key from hashed names plus the country and zip code. Matching can take up to 48 hours. Records that do not match may still be used for policy compliance checks, but not for Customer Match or any other Google product. After matching and policy checks, the file is marked for deletion.

Google's page on how Google uses Customer Match data states that uploaded files are used only to match your customers and to check policy compliance. Google says it will not use them "to build or enhance profiles of your customers", will not share them with other advertisers, and stores them encrypted.

Uploading and keeping the list fresh

In Google Ads you create the list in Audience manager (Tools, then Shared library) as a new Customer list, choose plain text or hashed data, select the CSV, tick the box confirming the data was collected and shared in line with the Customer Match policy, and set a membership duration. Google's Create a customer list page also describes connecting a data source instead of a file, including BigQuery, Google Cloud Storage, Amazon S3, MySQL, PostgreSQL, Salesforce, SFTP and Snowflake. Google now recommends Data Manager or the Data Manager API for Customer Match and suggests avoiding the Google Ads API for new integrations.

Lists age. Google says "Customer Match memberships expire after 540 days", and a list must have at least 100 members added or updated in that window to stay eligible. To keep it current you can edit the list to add customers, remove specific customers or replace all members, or keep it in sync automatically through Data Manager, an approved upload partner or a CRM connection. Google advises appending new data regularly rather than replacing whole lists.

List size, match rates and low volume

The troubleshooting page says "All files submitted must have a minimum of 100 user records". The list size you see afterwards counts matched people, so it is lower than the rows you uploaded: some customers have no active Google account, have turned off ad personalisation, or their data was not formatted or hashed correctly.

For ads to serve, a list needs enough active users at the moment the ad is shown. Google recommends "audience list sizes of at least 100 users to prevent ads from not serving", and notes that extra targeting restrictions on top of the list shrink it further. To improve match rates, Google suggests including several match keys, such as both email and phone, and adding the four-digit extension to US zip codes. Uploads take up to 48 hours to process, so a list you change every day may show "In progress" constantly.

Customer Match and Smart Bidding

One setting is easy to miss. According to About Customer Match, "Campaigns using Smart Bidding and optimized targeting automatically include all the Customer Match lists in your account". Google says this does not change your campaign's targeting settings; the lists are used to improve performance toward goals such as conversions. You can opt out of the automatic inclusion or remove lists from the account. Customer Match lists are not used with manual bidding strategies. Our guide to Google Ads budgets and bid strategies explains which strategies count as Smart Bidding.

Users in the EEA, UK and Switzerland

If your list includes people in the European Economic Area, Google's How to provide consent for Customer Match page says you must pass granted consent signals to use the data for ad personalisation, through the Google Ads API, a partner, Audience manager or conversion-based customer lists. Through the API, missing consent is treated as not consented, and that data "will not be processed". The policy adds that IP address and timestamp matching is not supported in the EEA, the UK or Switzerland. Since early March 2024, About Customer Match says lists can no longer serve on Google Partner Inventory or third-party exchange sites in the EEA, UK and Switzerland; Google's own properties remain available.

FAQ

Can a small Google Ads account use Customer Match?

Yes, if it has a good history of policy compliance and payments. All such accounts can use lists for observation and exclusions. The Targeting setting and manual bid adjustments need 90 days of Google Ads history and more than USD $50,000 total lifetime spend.

Do I have to hash the data before uploading?

No. In Google Ads you can upload plain text and Google Ads hashes the private fields with SHA256 before sending them. If you hash the data yourself, normalise it first and use hex SHA256. Uploads through the API must be hashed, and Country and Zip are never hashed.

How many customers does a list need?

Google says every file must have at least 100 user records and recommends audience list sizes of at least 100 users so ads do not stop serving. The list size shown counts matched, active Google users, so it is usually lower than the rows you uploaded.

How long do people stay on a Customer Match list?

Google says memberships expire after 540 days. A list needs at least 100 members added or updated within the last 540 days to stay eligible, so refresh it with uploads or an automatic sync.

Can I upload a list of email addresses I bought?

No. The Customer Match policy only allows customer information you collected in a first-party context, such as purchases on your website, sign-ups in your app or a loyalty programme in your store.

Want a website that collects customer details with clear consent and a privacy policy to match? See our website development service and all our services, or email [email protected].