Since Apple said they will be changing iOS to fix autocorrect, this will no longer be maintained or updated. I will leave the files and instructions here for future reference (in case Apple’s fix doesn’t meet people’s needs).
Files for adding obscenities to iPhone® to stop autocorrect
Easy mode adds a contact to your device contacts with all the words in the name. This will stop your phone from autocorrecting fuck to duck. It will not make your phone suggest the words and will not let you autospell them with swipe typing. For those you need to use Advanced Mode.
Advanced mode adds to your phone’s dictionary. This will make your phone suggest the words if you misspell them and allow you to use the words when swipe typing. This requires setup on a Mac® with the same iCloud Drive® account as your phone and will also add the words to your computer’s dictionary.
If you do not have access to a Mac, or are unable to use iCloud or iCloud Drive you will need to use Easy Mode which has limited functionality.
You can add additional words on your own Text frame. To share your dictionary with others or for more details on importing and sharing text replacements, see the official help article.
Note: this will also add these words to your computer’s dictionary. If you change or remove the words on the computer it will also do the same on your phone.
This project is not authorized, sponsored, or otherwise approved by Apple Inc. Apple logo®, iPhone®, Mac®, and iCloud Drive® are registered trademarks of Apple Inc.