Chromecast and smart TVs on guest WiFi with a captive portal

The TV over the bar shows a WiFi error, or a hotel guest's streaming stick sits on a "connecting" screen all evening. The guest WiFi is working for every phone in the building. These devices are failing because the network has a captive portal, and nothing on them can fill one in.

This guide is for venue owners, hotel managers and the installers who look after their networks. It explains why the problem happens, the two clean ways round it, and how to set up the fix on CaptiFi and on other controllers.

Why these devices get stuck

A captive portal holds every new device back until someone completes the sign-in page. A phone or laptop notices the portal through its automatic connectivity check and opens the page in a small browser window. A Chromecast, a Fire TV stick, a smart TV, a printer or a card machine runs a similar check, sees that it has no internet, and has no browser to show the page in. So it waits, tries again, and never gets online. Google's own support page says its streaming devices do not support networks that need a captive portal sign-in.

Some devices can sign in. An Apple TV hands the page to an iPhone or iPad to complete, and some smart TVs have a browser in a menu, but signing in through a TV remote is slow, and the device drops off again when the venue's session ends. A device that needs to stay online all day has to skip the portal altogether.

Two ways to get them online

If you have several of these devices, a separate staff network keeps them off the guest network entirely and is the tidier answer. Pre-authorising is the right answer when moving a device is not practical, such as a TV that guests need to cast to from the guest network.

Finding the device's MAC address

A MAC address is six pairs of letters and numbers, such as A4:77:33:0B:12:9F. A Chromecast stuck at a portal has usually not finished setup, so use the setup screen: on the Connect to Wi-Fi step in the Google Home app, tap More in the top right and choose Show MAC Address. After setup, the address is in the Google Home app under the device's settings, Device information, and on Chromecast with Google TV and Google TV Streamer it is under Settings, System, About, Status. Most other devices show it in their network or WiFi settings, and many have it on a label on the back or underneath. On UniFi, a device that has already joined the WiFi also appears in the controller's client list with its address.

Check the address in the device's own settings while it is connected to your guest network. Some devices use a private WiFi address in place of the hardware one, so the label on the box may not match what the network sees. A back-office iPad is the usual case: Apple's security guide says it uses a rotating address by default on open and captive portal networks, so set its Private Wi-Fi Address to Fixed for your guest network before you copy the address, or the address will change.

Pre-authorising a device on CaptiFi

1. On my.captifi.io, open My Locations and click Connection status on the venue's card.
2. Find the row "Printers, card machines, TVs and casting devices can skip the sign-in page." and click Pre-authorized devices.
3. Enter the device's MAC address, add a label if you want one (for example Bar TV), and click Add device. Colons, dashes or no separators are all accepted.

The option shows for venues on CaptiFi access points and for venues connected to a UniFi controller by a direct, API key or Remote Tunnel connection, and account owners and admins can manage the list. On other connections the panel says "Not available for this venue's connection yet."

On CaptiFi access points the device is allowed on every access point at the venue within a minute. It is allowed again automatically after an access point restarts or when the device next appears, and the list is re-checked daily. On a UniFi controller, CaptiFi authorises the device on the controller straight away and refreshes it every night, so it survives controller reboots; if CaptiFi cannot reach the controller at that moment, the device is saved and applied within a day. For a device that has never connected, add it once it has joined the WiFi so the controller can identify it.

A pre-authorised device never sees the sign-in page, is not counted as a guest and receives no marketing, so your guest numbers stay accurate. Removing it from the list takes the allowance away, and it then sees the sign-in page like any other device.

On other controllers

Most business WiFi controllers have their own way to let a device past the portal by its MAC address, under a different name on each, usually in the guest network or access control settings. If your venue runs a controller CaptiFi cannot pre-authorise devices on yet, use the controller's own setting or put the device on the staff network. Your hardware's setup guide covers the portal settings for each system.

Hotel rooms and guests' own streaming sticks

Some hotel and holiday-let guests travel with their own streaming stick and plug it into the room TV. It meets the same portal and stays offline. Two approaches work. The front desk can add the stick's MAC address for the length of the stay and remove it at checkout, which on CaptiFi access points applies within a minute and leaves the device out of your guest list. Or the property can provide in-room TVs on the staff network with their own casting system, so guests never need to bring a device.

Either way, put a line about streaming sticks on the room card or in the welcome information, so guests know to ask the front desk.

Online, but the phone cannot cast to it

Once a TV or Chromecast is online, a guest may still be unable to cast to it from their phone. Casting needs the phone and the TV to find each other on the network. Guest networks usually isolate devices from each other, so that one guest cannot reach another's phone, and that same isolation stops a phone from finding the TV. If casting matters, put the TV and the devices that cast to it on a network without client isolation, such as the staff network, or use the casting system your TV provider supports for shared spaces.

Is a bypass safe?

A MAC address is an identifier, and it can be copied by someone who sets out to do so. A pre-authorised address is a convenience for devices that cannot sign in, so do not rely on it to protect anything. It does not give the device access to your staff network or your tills; it only lets it onto the guest network without the portal.

Card machines and anything else that handles payments are usually better on their own password-protected network, and your payment provider's guidance takes priority over anything here. Remove devices from the list when they leave the venue, so the list stays short and every entry is something you recognise.

Troubleshooting

For anything else on the sign-in side, the guide to a captive portal that is not showing works through each cause in turn. To set up pre-authorised devices on your own network, start a 30-day free trial on CaptiFi access points or your UniFi controller; plans start from $69/mo on the pricing page.

Sources: CaptiFi customer documentation for pre-authorised devices and the UniFi setup guide, October 2026; Apple Platform Security, Wi-Fi privacy with Apple devices; Google, Find your Chromecast's MAC address and its captive portal note. Chromecast, Google Home, Fire TV, Apple TV and UniFi are trade marks of their owners; CaptiFi is not affiliated with or endorsed by them.