Start with the reason you want an alternative
If you already know the film, the fastest alternative is a title search on a service that lists viewing offers. If you are undecided, a genre collection or a recommendation may help more. If you need a specific subtitle language, confirm that requirement on the viewing edition rather than choosing by website name.
For one title across several services
JustWatch lets you select a country and look for a film or series. Check the year where names overlap. Availability can include subscription, rental, purchase and free offers, depending on the title and region. The same film can have different options in two countries.
For recommendations from other viewers
Reddit discussions can suggest films you had not considered, but a recommendation and a current viewing offer are separate things. Bring the title back to search, confirm its identity and choose an edition. Avoid reading detailed replies if you want to keep a mystery's ending unspoiled.
For a different browse without starting over
Try the nineties collection, comedy series or what-to-watch guide. Changing the mood can solve an indecisive evening more quickly than changing the entire website.
Searches for 123Movie alternatives often mention 123Movies, MoviesJoy or other similarly styled catalogs. Names alone do not establish shared ownership, shared accounts or the same available titles. Keep the movie name, production year and viewing requirement as the useful part of your search.