Expo Mobile Proxies: Dev Client and EAS Builds on a US Carrier Line
Expo gives React Native teams a development client, EAS builds and over-the-air updates, and the resulting app then runs on whatever network the user has. For US users that is a carrier network, with its latency, NAT behaviour and geolocation. A Mobile Proxies US line lets your Expo app run from that position: an emulator or device behind the line's SOCKS5 or HTTP endpoint, or a VLESS tunnel for everything including UDP. The line's exit IP and rotation are available in an API, so each test session can be tagged with carrier and metro.
What to test from a US mobile network
Your own API's geo gates and feature flags. Third-party SDKs that read connection type or region (payments, maps, analytics, auth). OTA update downloads at mobile bandwidth. Push notification registration and delivery paths. Web views that load region-dependent content. The dev client's own connection to your development server when you develop against a mobile network on purpose.
Build and submit steps on EAS are server-side and unaffected. The line is for the running app.
Routing the dev client and EAS builds
Android emulator: start it with a proxy pointing at the line's HTTP endpoint, or configure the emulator's network settings; for full coverage including UDP, run a local xray gateway from the line's VLESS link and point the emulator at its unauthenticated SOCKS port. iOS simulator: it uses the Mac's network, so set the Mac's system proxy or run the xray gateway and route through it. Physical device: Wi-Fi proxy or a VLESS client app.
Verify with an IP echo request from inside the app or from the device browser before running the suite. The address should match ip from GET /proxy/status for the line.
OTA updates and latency under cellular conditions
Publish an update and let a device behind the line fetch it. Measure download time on a 4G line (up to 25 Mbps download) and a 5G line (up to 50 Mbps). Observe how your app handles a slow or interrupted update; rotate the line mid-download to simulate a network change and check the retry.
Time your API calls from the line to each backend region you consider. US mobile latency to a US region versus elsewhere is a deployment decision measured, not guessed.
What the app reports about its own network
A proxy or tunnel on Wi-Fi does not turn the device into a cellular one. getNetworkStateAsync in expo-network will still say WIFI, and expo-location still reads the device's real position. Any branch in your app that keys on those values takes its Wi-Fi path even though the address is a carrier address. Test that deliberately: your backend sees a US mobile address while the client reports Wi-Fi, and the two should not contradict each other in your logic.
On a physical device, phone_profile_link from GET /proxies/my gives a live subscription for a phone proxy app, with format=singbox, clash or uri. If the tunnel covers everything, exclude your LAN or use a tunnelled dev server so the development client can still reach Metro. For EAS Update, publish to a dedicated channel and record the update id beside the exit IP from GET /proxy/status. Run the same update on 4G and 5G, and keep both results with their network_tier so the download times can be compared.
Rotation and terms
Rotate between sessions by API and confirm the address first. Rotate during a session only to test network-change handling.
Use your own Expo project, EAS account and backend within Expo's and each SDK provider's terms. Data on the line is not metered; the fair-use rule concerns only lines moving 60 GB in a UTC day repeatedly.
Setting up a Expo proxy on Mobile Proxies US
- Buy a line in a US metro; 5G if the app syncs large assets.
- Read endpoints from the API; set up the emulator proxy or a local xray gateway from the VLESS link.
- Confirm the exit IP from inside the app or the device browser matches ip from GET /proxy/status.
- Run the dev client or EAS build through geo-gated flows, OTA updates and API latency checks; log exit IP and carrier per case.
- Rotate between sessions; move the line to another metro for free for a second geography.
Expo proxy questions
Can the iOS simulator use the line?
Yes, through the Mac's network: set the system proxy to the line or run a local xray gateway and route the Mac through it.
Does the dev server connection go through the line too?
If you route the whole emulator or device, yes. Use a tunnel-based dev server URL or exclude your LAN in the xray routing rules.
Does EAS Build need the proxy?
No. Builds happen on EAS servers. The line is for the app at run time.