A Satoshi is the smallest divisible unit of Bitcoin on the base layer (Layer 1). One Bitcoin is equal to 100,000,000 Satoshis, and you cannot go smaller than a Satoshi on the Bitcoin blockchain itself—this is hardcoded into the protocol.

Layer 1 (Base Layer)

• Minimum unit: 1 Satoshi (0.00000001 BTC)

• Not infinitely divisible — any smaller division would require a protocol-level change (which would be extremely difficult and controversial).

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Layer 2 (e.g., Lightning Network)

On Layer 2, things are more flexible. Some L2 protocols may represent or use fractions of a Satoshi in their internal accounting:

• The Lightning Network, for example, allows the use of millisatoshis (msat) — where:

• 1 sat = 1,000 msat

• This enables finer granularity for routing fees and payments.

So while the base layer is not infinitely divisible, Layer 2 solutions can allow sub-satoshi units through their own internal systems.