How to set a custom ringtone on Samsung

Any Samsung Galaxy phone can use your own song as a ringtone. Make the ringtone first, then it takes a few taps in Settings.

Make the ringtone first. Pick the best part of a song in about 30 seconds.

Open Ringtone Maker

Step 1: Make the ringtone

Open the Ringtone Maker in Chrome or Samsung Internet and choose your song.
Drag on the waveform to pick the part you want, then choose MP3.
Press Make ringtone, then Download. It's saved in My Files → Downloads.

Step 2: Set it as your ringtone

Open Settings → Sounds and vibration → Ringtone.
If you have two SIM cards, pick SIM 1 or SIM 2.
Tap the + at the top right of the list.
Find your file (look in Downloads or under Audio), tap it and tap Done.

Only for one contact

Open Contacts and tap the person.
Tap Edit, then View more at the bottom.
Tap Ringtone, then +, pick your file and save.

As a notification sound

Go to Settings → Sounds and vibration → Notification sound and add your file the same way. Keep notification sounds short: 1 to 3 seconds works best. The audio cutter can trim a sound that short.

The song doesn't show up in the list

Check that the download finished: open My Files → Downloads and play it.
Restart the Settings app, or the phone, so it scans for new sounds.
Move the file to the Ringtones folder in My Files (Internal storage → Ringtones). Files there always show up.