Snarl is learned by 15 species by level, 136 by machine and 1 by tutor

Effect, in PokéAPI's words

“Has a chance to lower the target’s Special Attack by one stage.”

Who learns it

136 species in all, 8 of 10 games shown

Scarlet and Violet: 109 species

Species	Method	Level
Umbreon	Level up, Machine	Evolve
Mightyena	Level up, Machine	Evolve
Maschiff	Level up, Machine	7
Mabosstiff	Level up, Machine	7
Fuecoco	Level up, Machine	21
Crocalor	Level up, Machine	24
Skeledirge	Level up, Machine	24
Iron Jugulis	Level up, Machine	28
Ekans	Machine
Arbok	Machine
Vulpix	Machine
Ninetales	Machine
Meowth	Machine
Persian	Machine
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Feraligatr	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Spoink	Machine
Grumpig	Machine
Seviper	Machine
Crawdaunt	Machine
Chimecho	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Floatzel	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Weavile	Machine
Darkrai	Machine
Arceus	Machine
Samurott	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Axew	Machine
Fraxure	Machine
Haxorus	Machine
Cubchoo	Machine
Beartic	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Deino	Machine
Zweilous	Machine
Hydreigon	Machine
Thundurus	Machine
Litleo	Machine
Pyroar	Machine
Incineroar	Machine
Rockruff	Machine
Lycanroc	Machine
Solgaleo	Machine
Rillaboom	Machine
Cinderace	Machine
Toxtricity	Machine
Morpeko	Machine
Copperajah	Machine
Duraludon	Machine
Zacian	Machine
Zamazenta	Machine
Urshifu	Machine
Zarude	Machine
Glastrier	Machine
Spectrier	Machine
Calyrex	Machine
Fidough	Machine
Dachsbun	Machine
Bombirdier	Machine
Greavard	Machine
Houndstone	Machine
Kingambit	Machine
Iron Thorns	Machine
Wo-Chien	Machine
Chien-Pao	Machine
Ting-Lu	Machine
Chi-Yu	Machine
Roaring Moon	Machine
Koraidon	Machine
Miraidon	Machine
Walking Wake	Machine
Okidogi	Machine
Archaludon	Machine
Gouging Fire	Machine
Raging Bolt	Machine

Legends Arceus: 4 species

Species	Method	Level
Umbreon	Level up	Evolve
Murkrow	Level up	6
Honchkrow	Level up	6
Sneasel	Tutor

Brilliant Diamond and Shining Pearl: 36 species

Species	Method	Level
Umbreon	Level up, Machine	Evolve, 1
Mightyena	Level up, Machine	Evolve, 1
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine

Sword and Shield: 77 species

Species	Method	Level
Umbreon	Level up, Machine	Evolve, 1
Zeraora	Level up, Machine	1
Obstagoon	Level up, Machine	9
Yveltal	Level up, Machine	10
Nickit	Level up, Machine	12
Thievul	Level up, Machine	12
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Sneasel	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine
Lillipup	Machine
Herdier	Machine
Stoutland	Machine
Purrloin	Machine
Liepard	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Haxorus	Machine
Druddigon	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Hydreigon	Machine
Pangoro	Machine
Incineroar	Machine
Rockruff	Machine
Lycanroc	Machine
Golisopod	Machine
Silvally	Machine
Drampa	Machine
Tapu Bulu	Machine
Solgaleo	Machine
Guzzlord	Machine
Naganadel	Machine
Rillaboom	Machine
Cinderace	Machine
Yamper	Machine
Boltund	Machine
Toxtricity	Machine
Morpeko	Machine
Copperajah	Machine
Duraludon	Machine
Zacian	Machine
Zamazenta	Machine
Urshifu	Machine
Zarude	Machine
Glastrier	Machine
Spectrier	Machine

Ultra Sun and Ultra Moon: 71 species

Species	Method	Level
Mightyena	Level up, Machine	Evolve, 1
Yveltal	Level up, Machine	18
Zeraora	Level up, Machine	19
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Umbreon	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine
Darkrai	Machine
Arceus	Machine
Lillipup	Machine
Herdier	Machine
Stoutland	Machine
Purrloin	Machine
Liepard	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Druddigon	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Litleo	Machine
Pyroar	Machine
Pangoro	Machine
Furfrou	Machine
Incineroar	Machine
Rockruff	Machine
Lycanroc	Machine
Golisopod	Machine
Silvally	Machine
Drampa	Machine
Tapu Bulu	Machine
Solgaleo	Machine
Guzzlord	Machine
Naganadel	Machine

Sun and Moon: 69 species

Species	Method	Level
Mightyena	Level up, Machine	Evolve, 1
Yveltal	Level up, Machine	18
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Umbreon	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine
Darkrai	Machine
Arceus	Machine
Lillipup	Machine
Herdier	Machine
Stoutland	Machine
Purrloin	Machine
Liepard	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Druddigon	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Litleo	Machine
Pyroar	Machine
Pangoro	Machine
Furfrou	Machine
Incineroar	Machine
Rockruff	Machine
Lycanroc	Machine
Golisopod	Machine
Silvally	Machine
Drampa	Machine
Tapu Bulu	Machine
Solgaleo	Machine
Guzzlord	Machine

Omega Ruby and Alpha Sapphire: 60 species

Species	Method	Level
Mightyena	Level up, Machine	18
Yveltal	Level up, Machine	18
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Umbreon	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine
Darkrai	Machine
Arceus	Machine
Lillipup	Machine
Herdier	Machine
Stoutland	Machine
Purrloin	Machine
Liepard	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Druddigon	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Litleo	Machine
Pyroar	Machine
Pangoro	Machine
Furfrou	Machine

X and Y: 60 species

Species	Method	Level
Yveltal	Level up, Machine	18
Growlithe	Machine
Arcanine	Machine
Mew	Machine
Umbreon	Machine
Murkrow	Machine
Snubbull	Machine
Granbull	Machine
Sneasel	Machine
Houndour	Machine
Houndoom	Machine
Raikou	Machine
Entei	Machine
Suicune	Machine
Larvitar	Machine
Pupitar	Machine
Tyranitar	Machine
Poochyena	Machine
Mightyena	Machine
Nuzleaf	Machine
Shiftry	Machine
Sableye	Machine
Electrike	Machine
Manectric	Machine
Carvanha	Machine
Sharpedo	Machine
Crawdaunt	Machine
Absol	Machine
Shinx	Machine
Luxio	Machine
Luxray	Machine
Honchkrow	Machine
Stunky	Machine
Skuntank	Machine
Spiritomb	Machine
Drapion	Machine
Weavile	Machine
Darkrai	Machine
Arceus	Machine
Lillipup	Machine
Herdier	Machine
Stoutland	Machine
Purrloin	Machine
Liepard	Machine
Sandile	Machine
Krokorok	Machine
Krookodile	Machine
Scraggy	Machine
Scrafty	Machine
Zorua	Machine
Zoroark	Machine
Druddigon	Machine
Pawniard	Machine
Bisharp	Machine
Vullaby	Machine
Mandibuzz	Machine
Litleo	Machine
Pyroar	Machine
Pangoro	Machine
Furfrou	Machine