Toby Fox has previously stated the game will have only one ending. However, on Deltarune's Steam page, the statement is worded somewhat mysteriously, and another route has been discovered in Chapter 2.
I will resolve this question to YES if the full version of the game (including all chapters) has just one ending. I will not count a few changed lines of dialogue as a different ending, it needs to be clearly distinct. Additionally, this question is only about the ending of the game, and not about any possible divergences before that point (e.g., if taking the Snowgrave route in Chapter 2 leads to the same end as taking any other route, this question will be resolved to YES).
If Deltarune is never fully released, this will be resolved to N/A.
Update 2026-06-18 (PST) (AI summary of creator comment): Regarding intentional softlocks on a weird/alternate route:
If the softlock is a deliberate end state with no way to reach the normal ending, this counts as a distinct ending and resolves NO
If the softlock is merely a fail state (like a game over) that still allows the player to continue and reach the main ending, it does not count as a separate ending
1,000@Ibozz91 Oh, that's an interesting question. If there's an intentional softlock that effectively makes it impossible to reach the "normal" ending from a weird route save, I'd resolve the question as NO, since the game has reached a deliberate end state that's distinct from the main ending (even if no credits roll). As an example, if Undertale's genocide route, after choosing ERASE or DO NOT, were not to show any dialogue after 10 minutes in the black screen that follows and it'd just stay in that state forever with no way to interact, I'd still say "the genocide route has a different ending than the neutral route". On the other hand, if the potential weird route softlock isn't clearly an end state (e.g., it's just a fail state like a game over, where the game still allows you to continue and reach a minimally changed main ending), this wouldn't count as a proper ending.