Ubuntu + Firefox has become my daily driver. I would like to be able to send iMessage from Firefox. I am able to login using my Apple ID in Firefox. Is there a URL that can enable me to send iMessage from Firefox?
No. iMessage (rebranded as Messages) service is only implemented on Apple hardware and it is not available for other desktop/mobile/web platforms. Apple does offer web apps for other parts of iCloud but not iMessage or FaceTime.
You need an Apple device, specifically running either iOS (iPhone, iPad, iPod touch), macOS (Mac desktops and MacBook portables) or watchOS (Apple Watch) to access Messages via native app available for each platform.
Messages is not accessible using other Web browsers such as Firefox, and not available even using Apple's own Web browser Safari.
If you have a jailbreakable iOS device, you can install the Remote Messages package.
Features(from the package description):
- SMS and iMessage support
- File/media attachments
- Camera roll access
- Emoji support
- Message searching
- Typing notifications
- Contact pictures
- Custom Themes
- Phone status icons
- Connects to Address Book
- SSL Support and username/password authentication
- Utilises WebSockets for perfect synchronisation with device
- Runs as a background service with a small memory footprint
- Install the "Remote Messages (iOS 9)" package in Cydia or Sileo.
- Navigate to "Remote Messages" in Settings.
- Set the username and password you wish to use.
- Slide the toggle to start the server. Allow a few seconds for this to complete. If it does not work, restart your device and try again.
- Make sure your device is connected to the same WiFi network as your computer.
- In the "Remote Messages" settings panel, note the IP address displayed at the top.
- Enter the IP into the address bar of your web browser. For example: http://192.168.0.5
- At the prompt, authenticate using the username and password you set
Clearing up some misconceptions about jailbreaking:
- Jailbreaking is 100% legal and Congress has issued a special DMCA exception allowing jailbreaking
- As long as you remember to unjailbreak before going to the Apple Store your warranty will not be affected
- Jailbreaking can easily be reverted without losing your data
- This package/tweak does not affect the security or encryption of iMessage, because it requires a physical device and "pretends" to be an actual user typing in a message