You might see a number higher than 25 when searching online. That is because Season 1 also has . These are bonus side-stories not originally broadcast on TV.
To give you context for your watchlist:
(AoT) Season 1 consists of 25 episodes . Originally aired between April and September 2013, this season was produced by Wit Studio and covers the first four major story arcs of Hajime Isayama’s manga: the Fall of Shiganshina, Humanity's Comeback, the Struggle for Trost, and the Female Titan arc. Attack on Titan Season 1 Episode Breakdown how many episodes in aot season 1