What app or program do I use to open a chat.db-wal file
chat.db-wal (besides chat.db and chat.db-shm) is a part of the sqlite3 database managing all your messages sent and received by the app Messages.

So the main app using this database as a "client" is Messages.

The purpose of the file chat.db-wal is to provide atomicity and durability in database systems by write-ahead logging (WAL).

You can open the file explicitly by using any text editor (which I don't recommend) and implicitly by using a SQLite3 GUI like DB Browser for SQLite 3.9.0 or sqlitestudio 3.1.0.



Better create a copy of all database files and use these to tinker with them.