Developing a chat or
There are many services that provide a back-end for message storage while providing API & SDK for developers to create a messaging app easier.
What these services offer:
- Server for messages storage
- SDKs for app development
- Push notification support
- One-to-one, group, and cross-platform chat support

Table of Contents
SendBird
SendBird offers chat API and SDK to develop a chat app with real-time communication among its users. SendBird’s chat API is cross-platform, which allows its apps and games to run on multiple platforms including iOS, Android, JavaScript, Unity, and .NET(+Xamarin).

Applozic
Applozic allows real-time messaging on multi-platforms. It provides a simple SDK which allows users to share images, files, locations, and audio/video conversations. Applozic has typing indicator feature that lets the receiver know when the sender is typing. It shows the message status and delivery report so the user to understand whether his message is delivered.

Layer
Layer provides everything you need, from UI to infrastructure, to boost retention, and engagement or drive transactions with the power of rich messaging. Layer supports multi-part messages with any payload type — location, text, photos, GIFs, voice, video, or just plain meta-data. It allows a payload of up to 2GB to be sent.

If you want to know Layer’s price, you need to contact its sale department at https://layer.com/pricing.
Pusher
Pusher offers a simple, event-based API to develop chat messages which can be delivered to any device and any platform. Similar to other services, Pusher can show the offline/online status of users in real-time and allow developers to grant permission to specific channels.

PubNub
PubNub offers low-latency real-time messaging across any device. PubNub can send a message between any two devices on earth in a blink of an eye. It has simple APIs and SDKs to connect, build, and scale real-time applications on the PubNub Data Stream Network

Hi Android Names! I’m John at SendBird. Thank you for covering SendBird. I really appreciate your interest! As a small update, we have discontinued the standard pricing and have switched over to custom pricing model. Would it be okay if you can update the pricing grid to our current one? Thank you! =)
Thanks for contacting me with new information.