If you're looking to catch up on 'Naruto' filler episodes without spending a dime, there are a few places I usually check out. Crunchyroll used to have a lot of them, but their free tier can be a bit hit or miss with ads. TubiTV is another solid option—they rotate their anime library often, but I’ve stumbled upon 'Naruto' there more than once. Just be ready for commercial breaks, though they’re not too intrusive. Sometimes, I even peek at PlutoTV’s anime channel; it’s like old-school TV but with random episodes, so you might get lucky.
For a more direct approach, I’ve heard good things about sites like 9anime or Zoro.to, but I’d recommend an ad blocker if you go that route. I’m always a little wary of unofficial sites, but they do tend to have everything—fillers included. Honestly, I think the filler arcs get too much hate. Sure, some are forgettable, but others, like the 'Chikara' arc, actually have cool animation and expand the world. It’s worth digging around to find those hidden gems.