Meta’s API v27 Quietly Flips Two Ad Defaults — What to Check Before Your Next Launch — Harsh Sahu

Meta changed two ad defaults last week, and most advertisers will never notice — until the change shows up in their results.

On 4 November 2026, Meta released Graph API v27.0 and Marketing API v27.0. The announcement came from Meta’s own developer blog — “Graph API and Marketing API version launch”, 4 November 2026 — and two of the changes quietly flip settings to “on” for new ads built through software. If your agency or your tools build ads through the API, this one is worth two minutes of your time.

Change 1: Meta may add a product showcase to your ad

Product showcase is the row of catalogue items that can appear under your ad’s main image or video. From v27.0, when an ad is created through the API without any product showcase setting, Meta may switch it on by itself — but only when it has high confidence that a specific product set in your catalogue matches the ad.

For a shop, that can be helpful. For a service business — a clinic, a salon, a consultancy — a row of products appearing under your ad is not what you asked for, and it changes what the customer sees first. The opt-out exists: your tool or agency can set the product showcase enrolment to opt out. But someone has to know to do it.

Change 2: Your device targeting may quietly expand

The second change affects new Sales ad sets that target specific mobile devices or operating systems. From v27.0, if the ad set leaves the device-expansion setting blank, Meta switches on “Reach more people across other mobile devices” by default — and your ad can then be shown on phones and operating systems you never chose.

Existing ad sets are not changed. The change does not apply to ad sets that count conversions in a mobile app, or to special ad categories like housing. Meta says the new default will reach older API versions in about 90 days, around February 2027. To keep delivery inside the devices you actually chose, the setting has to be set to zero explicitly — an omission is now a choice.

One more date: 10 November

The same announcement notes that Marketing API v24.0 stops being available on 10 November 2026 — tomorrow. If any tool you rely on still calls v24.0, it can break. Worth one message to your agency or vendor today: “Which API version are we on?”

What this means for appointment-based businesses

Be honest about the scope: if you build your ads directly in Ads Manager, these two defaults do not touch you — Meta’s announcement describes only the API, and it does not say whether the same defaults apply in Ads Manager. But if your agency uses third-party buying tools, dashboards or in-house scripts — and many do — these changes reach your account through them.

So here is the check, before your next launch:

1. Ask your agency or tool vendor whether your ads are built through the API, and which version.
2. If they are: confirm product showcase is off unless you want it, and confirm your device targeting is set exactly as you chose it.
3. Mark 10 November in your calendar and confirm nothing you use still runs on v24.0.

The lesson is bigger than this one update. Meta changes defaults quietly, and the advertisers who get hurt are the ones who assume “nothing changed because I changed nothing.” A two-minute settings check at launch is cheaper than a month of budget spent on the wrong devices.

---

Source: Meta for Developers blog, “Graph API and Marketing API version launch”, 4 November 2026 — verified 9 November 2026. Harsh Sahu is the founder of ClientBooked Media, where he builds psychology-led Facebook and Instagram ad campaigns for appointment-based businesses: https://harshsahu.in/what-i-do/