Soutenir vs. supporter
While both soutenir and supporter can be translated as "to support", they are not interchangeable. Soutenir implies active and positive backing, whereas supporter most often means to tolerate or endure, making it a classic "false friend" for English speakers.
Soutenir
B1This word implies active, positive support. Use soutenir when you mean to hold something up physically, to back a cause or a person, to provide emotional or financial help, or to maintain an argument.
Les piliers en marbre soutiennent le toit du temple.
(The marble pillars support the temple's roof.)
Je soutiens ta décision, même si elle est difficile.
(I support your decision, even if it is a difficult one.)
Ses amis l'ont soutenu tout au long de cette épreuve.
(His friends supported him throughout this ordeal.)
Cette organisation soutient les artistes locaux avec des bourses.
(This organization supports local artists with grants.)
Le témoin soutient que l'accusé est innocent.
(The witness maintains that the accused is innocent.)
Elle n'arrivait pas à soutenir son regard.
(She could not hold his gaze.)
Il doit soutenir sa thèse devant un jury la semaine prochaine.
(He has to defend his thesis in front of a jury next week.)
Supporter
A2The primary meaning of supporter is to tolerate, endure, or put up with something, often something negative. It can also mean to physically bear a load or, in a very common anglicism, to be a fan of a sports team.
Je ne supporte pas son arrogance.
(I cannot stand his arrogance.)
Elle supporte difficilement la chaleur en été.
(She has a hard time tolerating the heat in the summer.)
Cette étagère peut supporter jusqu'à vingt kilos.
(This shelf can bear up to twenty kilos.)
L'entreprise supportera tous les frais liés au projet.
(The company will bear all costs related to the project.)
Depuis qu'il est petit, il supporte l'équipe de France de football.
(He has been a fan of the French national football team since he was little.)
Comment peux-tu supporter ce bruit toute la journée ?
(How can you put up with this noise all day long?)
Summary
In essence, use soutenir for positive and active support like backing a friend, a cause, or an idea. Use supporter when you mean to tolerate or endure something unpleasant. The main exceptions are when supporter means to physically bear a weight or, colloquially, to be a fan of a sports team.