A notification tone is just a very short, distinctive sound — think 3 to 8 seconds — that you'll recognize instantly when your phone buzzes. Making one is the same idea as a ringtone, only shorter and punchier. You can cut one from any sound in your browser in a couple of minutes.
This uses the free AudioTrim editor, and your file stays on your device.
Copy the MP3 to your phone, then go to Settings → Sound → Notification sound (or Default notification sound) and pick your file. Many phones also let you set per-app notification sounds.
iPhone notification and text tones are managed through GarageBand (import the clip, then share it as a ringtone) and selected under Settings → Sounds & Haptics. Apple caps tones at 30 seconds, so a short clip is well within range.
3–8 seconds is the sweet spot. Text tones can be even shorter — a second or two of a distinctive sound.
Mainly length. Ringtones run 20–30 seconds since the phone rings a while; notification tones are short bursts. The editing steps are the same. See how to make a ringtone.
Yes — a song, a chime, even your own recorded voice. For personal use, sounds you own are safest.
MP3 works across Android directly; for iPhone you'll convert it to a ringtone via GarageBand.
Related: How to make a ringtone · How to add fades · All guides