Short answer
Xfinity, AT&T, Spectrum and many Verizon routers don't let you change DNS. The quickest fix is to set up Sheepdog Filter on each child's device instead, which also works away from home. The fuller fix is to plug a mesh router (eero, Deco, Nest Wifi) into the internet-company box and set DNS there.
Why the setting is missing
Internet companies lock down their gateways so their own support and features work. That usually includes the DNS setting. Some Verizon Fios routers do allow it under Advanced › DNS Server; most Xfinity, AT&T and Spectrum boxes don't.
Option 1: Protect each child's device (quickest)
Set Sheepdog Filter on your kids' own devices. It takes a minute per device, and it works on mobile data and at friends' houses too, which router filtering never does.
Option 2: Add your own mesh router (best coverage)
If your Wi‑Fi doesn't reach every room anyway, this fixes two problems at once. Plug an eero, TP-Link Deco or Google Nest Wifi into your internet-company box, let it run your Wi‑Fi, and set Sheepdog Filter on it. Then follow the guide for eero, Deco or Nest Wifi.
Option 3: Consoles and TVs
For a games console or TV you can't set up through the router, set the DNS on the device itself: see the Xbox, PlayStation, Switch and smart TV guides.
Sheepdog Filter
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Start freeQuestions parents ask
Does Xfinity let you change DNS?
Most Xfinity gateways don't allow custom DNS. Protect your kids' devices directly, or add your own router behind the gateway.
Can I use the internet company's own parental controls too?
Yes. They can run alongside Sheepdog Filter. Most are basic site blockers without per-child rules or reports.
Will changing DNS slow down my internet?
No. DNS lookups take milliseconds and happen once per site. Streaming and downloads go straight to the internet as normal.
What if my home internet address changes?
Sheepdog Filter notices when your internet company changes your home's address and re-links your router automatically.