- Killing an enemy adds a fly to the jar, up to a maximum of 20.
- Upon use, releases Blue Flies equal to the number of flies in the jar.
- This item belongs to the Beelzebub set. Collecting three items from this set will transform Isaac into a giant humanoid fly.
- Kills by blue flies and locusts (including flies from the jar) and shooting familiars (including Incubus) do not add flies to the jar.
- Blue spiders, orbital familiars, and chasing familiars do add flies to the jar.
- Friendly enemies such as from the Friendly Ball add flies to the jar, but not those spawned from other enemies.
- Batteries do not affect the number of flies in the jar.
- Enemies must be actually killed to add a fly; transformations (such as Gapers turning into Pacers) or knockouts (such as incapacitating a Globin) do not count as kills.
- Destroying a shopkeeper will count as a kill.
- With items that kill normally unkillable enemies, killing things like Stone Grimaces will add flies to the jar.
- Killing minions in the Hush fight does not add flies to the jar.
- Fish Tail: Doubles the number of flies that spawn.
- Hive Mind: Flies are bigger and deal double damage.
- Schoolbag: Flies will be gained even while the Jar of Flies is in the inactive slot.
- Car Battery: No effect.
- Uranus: Enemies frozen by Uranus do not grant extra flies, even if shattered. Only enemies killed with bombs will add flies.
- Void: Flies will not collect when absorbed by Void, making the interaction worthless.
- The item's pickup quote references the tagline of the Pokémon games. The quote said "Gotta catch 'em all?"
- With Booster Pack #2, this item's sprite fills up with more flies depending on how many flies it contains. This is based on this Steam Workshop mod by Stewartisme.
- The item is likely a reference to the Alice In Chains album of the same name.
PC KTHW HTAY (First floor, in the shop)
|Bug!||The synergy of The Ludovico Technique with Brimstone or Technology will not spawn flies.|
|The Binding of Isaac: Rebirth|
|Achievements||Attributes||Bosses||Cards and Runes||Challenges||Chapters|