Push Notifications vs SMS: Differences and When to Use Each

Which is more reliable: push or SMS?

SMS is the more dependable path for must-arrive messages. Push depends on the device, the app, the permission, connectivity, battery settings and Google or Apple.

Google states plainly that FCM provides no delivery guarantee: a message ID only means FCM accepted the message, and actual delivery depends on factors such as device state and battery-saving delays. If a device is offline, FCM stores the message and delivers it on reconnect until its time-to-live expires (up to four weeks, which is also the default), and a time-to-live of zero discards anything that cannot be delivered immediately. If the app was uninstalled, the token becomes invalid and later sends fail.

SMS has its own failure modes: filtering, unregistered sender IDs, handset off, number changed. But it gives you a delivery report from the network, and it does not depend on an app. Read our guide to SMS not delivered for the diagnosis steps.

For time-sensitive push, set a short time-to-live so a "your driver is outside" alert does not arrive tomorrow, and use a collapse key so newer updates replace older ones. Both are fields in our push API.

Which channel should you use for which message?

Choose by what happens if the message is missed.

For an OTP in particular, see our guides on OTP messages and WhatsApp OTP vs SMS OTP.

How do you combine push and SMS?

Send push first and let SMS rescue what matters. The design has four parts:

1. An order of channels: push, then SMS.
2. A trigger: push not opened or acted on within a timeout, or no active device token.
3. A timeout per message type: a login code may justify seconds; a payment reminder may justify an hour.
4. A stop rule: if the user acts in the app, cancel the pending SMS.

Skip the SMS for low-value messages, where a missed push costs nothing. Our article on channel fallback strategy explains the order and stop rules, and the push channel page shows how push sits next to SMS and WhatsApp in one platform. Delivery statuses arrive through one webhook format (see webhooks), so your system can decide whether to fall back.

A fallback SMS should stand on its own and fit one message. This one is 85 characters, GSM-7, 1 message (limit 160): Payment of order 8842 was declined. Open the app to update your card: example.com/pay. An OTP version is 67 characters, GSM-7, 1 message: Your login code is 482915. It expires in 5 minutes. Never share it. A single emoji or curly quotation mark would turn either into Unicode and cut the limit to 70, so preview in the SMS character counter.

How do you measure push and SMS fairly?

Use the same funnel for both: sent, delivered or accepted, opened or clicked, and converted. Do not compare an SMS "delivered" rate with a push "sent" count, because they mean different things. A push "accepted" by FCM is not a push seen by a person.

• Reach: the share of your target users who can receive each channel.
• Delivery: operator delivery reports for SMS; accepted and, where your app records it, displayed or opened events for push.
• Action: link clicks, in-app events and conversions, attributed to the channel that was last touched.
• Opt-out and uninstall: complaints, STOP replies, permission revocations and uninstalls after sends.
• Cost per outcome: total channel cost divided by completed actions, not cost per message.

The messaging ROI calculator and our omnichannel messaging ROI business case show how to compare channels on outcomes.

A worked example: a Dubai food delivery app

"Souq Bites" (synthetic) has an app with a share of customers who allowed notifications and a larger web audience. It sends order status updates by push with a short time-to-live and a collapse key so the latest status replaces earlier ones. The OTP for new sign-ups goes by SMS because new users have no app permission. For existing users, the OTP goes by push; if the code is not used within a short timeout, an SMS follows from a registered sender ID. Promotions go by push only to users who allowed notifications and opted in to offers. Lapsed users, who may have uninstalled the app, receive a win-back SMS only if they gave SMS consent.

What are the common mistakes?

• Treating the push permission as marketing consent.
• Sending OTPs by push only, leaving users without the app or notifications stranded.
• Sending the same promotion on push and SMS at once.
• Leaving time-to-live at the default for time-critical messages.
• Comparing "accepted by FCM" with "delivered by operator" and calling push the winner.
• Using SMS for everything, paying per message for alerts that a push would handle.
• Ignoring stale tokens after uninstalls, which inflates push send counts.

How OmniChannels.ai helps

OmniChannels.ai sends push notifications and A2P SMS from the same REST API and platform, alongside WhatsApp, RCS, email and other channels. Push supports user, token, topic and segment targeting, templates, deep links, a collapse key and a time-to-live. SMS runs over BroadNet's direct operator connectivity, and channel fallback is configured per use case with statuses normalised into one webhook format. Read the push API docs, see the push notification channel, or talk to our developer team.