VoIP and GSM: how your Onoff calls work

Rev Ops
Rev Ops
  • Updated

Your Onoff calls go over the internet (VoIP) by default. When the internet connection is too weak, they can go over the regular mobile network (GSM). This article explains both modes and when each applies.

The two modes

VoIP (default)GSM
NetworkWi-Fi or mobile data (4G/5G)Mobile network, through your phone's SIM card
CostBased on your Onoff plan, no roaming feesYour mobile operator's rates, including roaming
Several devicesYes, up to 3No, one phone only
Without internetNoYes

To choose the mode, turn the Call via Wi-Fi/data option on or off in the app.

The GSM mode described here is different from Onoff Calls, which uses another technology. See "Onoff Calls: receive your calls over the mobile network".

Which mode to use

SituationRecommended mode
Good Wi-Fi or 4G/5G connectionVoIP
Weak internet but good mobile signalGSM
Travelling abroadVoIP, to avoid roaming fees
Several numbers on one phoneVoIP

How VoIP works

Your voice is converted into data, sent over the internet in small packets, then played back to the other person in near real time. This is what lets you use the same number on several devices, call from abroad without roaming and assign numbers without SIM cards.

For good call quality

  • Use a stable Wi-Fi or 4G/5G connection.
  • Avoid large downloads or streaming during calls.
  • Keep the app up to date.

Recognized mobile numbers

Onoff numbers are real mobile numbers, recognized by operators and most services: bank verifications, two-factor authentication codes, apps, delivery services. See "Receive SMS from special services".

Security

All Onoff communications are encrypted.

Related articles

  • Onoff Calls: receive your calls over the mobile network
  • Gateway numbers
  • Web app call preferences

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