A diagnosis needs both power and quality
RSRP estimates received reference-signal power, while RSRQ and SINR help reveal interference and radio quality. Strong power with poor quality can feel slower than a weaker but cleaner connection.
Screenshot OCR runs on your device
The OCR engine is downloaded only when requested and runs in a browser worker. The selected screenshot is not sent to Cell Tower Locator or an external recognition service. Always review extracted values before using the diagnosis.
Use repeatable measurements
Capture readings in the problem location, near a window and outdoors while keeping the same iPhone and carrier. Pair each radio reading with a speed test because congestion, backhaul and server performance are not visible in Field Test Mode.
Frequently asked questions
How do I open Field Test Mode on iPhone?
Open the Phone app, enter *3001#12345#* and press call. Available menus and measurements vary by iPhone, modem, carrier and iOS version.
Does the screenshot get uploaded?
No. OCR and diagnosis run locally in the browser. The page does not upload or store the selected screenshot.
Why did OCR miss a value?
Small text, dark mode, compression, unusual layouts and OCR ambiguity can affect recognition. Paste the text or correct the manual fields before running the diagnosis.
Can good radio readings still produce slow data?
Yes. Network congestion, limited spectrum, backhaul, traffic management, VPNs and the remote server can reduce speed even when RSRP and SINR are good.