CDSL (Central Depository Services Limited) is one of India's two securities depositories. It holds shares — including unlisted shares — in electronic (demat) form so they can be transferred without paper certificates. Most discount brokers (Zerodha, Groww, Upstox) open demat accounts on CDSL.
Why it matters to you
When you buy unlisted shares, they are credited to your demat account held with either CDSL or NSDL. The two are interoperable, so it does not matter which one you use — but you do need to give the seller the correct depository details so the shares land in the right account. A CDSL account number is a 16-digit numeric BO ID.
Example: A buyer shared their NSDL details by mistake while holding a CDSL account; the transfer bounced until corrected. See documents needed to buy unlisted shares.