500 Filler Percentage: ~38%
Everything else is —episodes created by the anime studio to let the manga get ahead. Filler can be fun, but it’s not part of the official storyline. Characters won’t reference it later, and it doesn’t change the plot.
Shippuden intersperses filler throughout the series rather than lumping it all at the end, though it has several long filler stretches.
Naruto episode canon refers to the episodes that are part of the original manga storyline created by Masashi Kishimoto. These episodes are considered "canon" because they follow the original narrative and character development. On the other hand, filler episodes are those that deviate from the original storyline and are created specifically for the anime series.
Note: Shippuden scatters filler inside canon arcs. Always check an online canon guide before pressing “next episode.”