Meta's new on-device conversions setting and what it means for UK brands

On 12 November, Meta switches on a new pixel setting called "Measure conversions on customer devices". It's on by default, and it lands about two weeks before Black Friday.

You've probably read that it doesn't apply in the UK. That's partly true. Whether it affects you depends on where your customers are and how your site is built, so here's what we know and what we're doing about it for our clients.

What the setting does

Up to now, Meta has matched ad views to purchases on its own servers. With this setting on, some of that matching happens on the shopper's phone or laptop instead.

The device uses details the shopper has already given you, such as an email address, plus temporary device information. Meta says that identifying data isn't sent to Meta during matching. All it receives is confirmation that a conversion happened and which campaign gets the credit.

A few things stay the same:

• It runs alongside the Meta pixel and the Conversions API (CAPI).
• Your attribution window and attribution model don't change.
• You don't need to set anything up. Eligible pixels get it switched on automatically.

In practice, expect Meta to report more conversions, a lower CPA and a higher ROAS. That doesn't mean you're selling more. It means more of the sales you were already making get linked back to your ads.

Does it apply to UK brands?

Meta says the setting is not active for people located in the EU or the UK. The key word is people. The exclusion depends on where the shopper is, not where your business is based. So for a UK brand there are three likely cases.

You only sell to UK customers.

It won't be active for your shoppers, and your reporting shouldn't change.

You sell internationally.

It will be active for shoppers outside the UK and EU, such as in the US or Australia. Your UK numbers stay the same, but conversions from those markets could start to rise from 12 November.

If your site has guest checkout, or your pixel loads in an iframe, you may not be eligible at all.

Reports of Meta's help pages list two requirements. The pixel has to load directly on the page, not inside an iframe or as an image-only pixel, and the site has to require people to log in with an email address or phone number.

Most Shopify stores let people check out as a guest. Pixels added through Shopify's customer events also run in a sandbox, not directly on the page. Either one could rule you out.

What we're doing over Black Friday

We're turning the setting off on our clients' pixels until peak is over, and we'll switch it back on in early December.

Black Friday already brings bigger budgets, higher auction costs and unusual buying behaviour. If Meta changes how it counts conversions in the same few weeks, you can't tell what's actually driving the results. Keeping it off also means this year's peak is measured the same way as last year's, so your year-on-year comparisons still hold up.

For most UK-focused brands, turning it off costs almost nothing. It probably wasn't active for their customers anyway. If you sell heavily into the US or other markets outside the UK and EU, the trade-off is more of a judgement call.

To check or change the setting:

1. Open Events Manager and go to Datasets.
2. Select your pixel and open the Settings tab.
3. Find "Measure conversions on customer devices" under Meta pixel settings and switch it off.

It's worth checking even if you think you're not eligible. The eligibility rules don't appear in the settings panel itself.

What's still unclear

Meta hasn't published much detail yet, so a couple of things are still open.

Double counting

It's not clear how on-device matches are deduplicated against events already coming in through the pixel and CAPI.

The source of the UK exclusion.

The UK and EU exclusion and the eligibility rules come from Meta's help pages. They're not in the settings panel or the notice Meta sent advertisers. We'll update this post once we've seen it working in a live account.

What to do now

Check your toggle before 12 November and decide whether you want it on through peak. Whatever you decide, keep checking Meta's numbers against your own order data. A jump in reported conversions with no change in orders comes from a change in how they're measured, not from better performance.