06 From zero · Crypto markets

Where you buy and who holds it

Almost everyone buys their first crypto on an exchange. The balance on that screen is not the same thing as holding the coin — and the difference has a name.

Renato UlianovOpening · 17 s · in Portuguese

The sentence
I bought on the exchange, which kept custody, and then made a withdrawal to my own wallet, keeping the recovery phrase on paper.

Blurred on purpose. Five words, and the second one changes everything.

The front door

What a crypto exchange is

It is a company. It takes your money from the bank, matches your order against someone else's in an order book — the same book as lesson 02 of the other track — and records in its own system that you now hold so much of some coin.

Notice the verb: records. While the coin sits there, it has not moved on the network. What exists is a row in a company's database saying it owes you that. This is not a flaw — it is how the thing works, and it is what lets you buy in seconds with no network fee.

What changes everything is knowing it. Because the actual coin, the one that exists in the public ledger from the earlier lessons, is held in a wallet belonging to the exchange — and that wallet's key is theirs.

Custody

Who holds the key

Custody is the word for “who holds the key”. There are two arrangements, and the difference between them is not about comfort: it is about who answers when something goes wrong.

Neither is wrong. What is wrong is thinking you are in one when you are in the other.

On the exchange In your own wallet
Who holds the keyThe companyYou
What you holdA claim on themThe coin in the ledger
Wrong addressThey may be able to reverse itThere is no reversing
Forgot the passwordRecover it with IDThere is no recovery
Who can freeze itThey can, or a court orderNobody
If the company failsYou become a creditorNothing changes for you
The two columns are the same pair of trade-offs seen from opposite sides: everything the exchange can undo for you, it can also do without you. And everything nobody can take from you in your own wallet, nobody can give back.
The withdrawal

Why transfers inside an exchange are free

Here is the detail almost no explanation mentions, and which on its own clears up half of a beginner's confusion.

If you send crypto to another customer of the same exchange, nothing goes through the network. The company subtracts from one row of its database and adds to another. That is why it is instant and why it is free: no transaction ever happened.

A withdrawal is a different thing. There the exchange really does have to send a transaction from its wallet to yours, in the public ledger, and pay the network fee for it. Tap both buttons and see where each one moves.

The exchange's database
The network
The accounts and amounts are made up. What is real is the shape: inside an exchange, transferring is editing a database; withdrawing is publishing a transaction.
How to choose

What you can check before depositing

No badge guarantees an exchange. What exists are signals, and the most misread of them is registration: in several countries a company that moves money has to enrol in a public register. Enrolling is an obligation, not an approval — nobody assessed the company to grant it.

What actually helps is duller and more useful: how long it has operated, whether withdrawals work without drama, whether support answers, whether fees are written before rather than after. And the rule that always holds: a large idle amount does not sit on an exchange. Buy there, keep it in your own wallet.

The proof

Now read the sentence

It's the same one from the top, unblurred. Tap each highlighted part.

I bought on the , which kept , and then made a to my own , keeping the on paper.
Start here

Five words

Two are the company, two are you, and one is the paper in a drawer. Tap one.

Five taps and the sentence is done.

You can already answer these

If this landed, the lesson did what it promised

  • On an exchange the key is the company's and you hold a claim on them.
  • In your own wallet the key is yours and there is no password recovery.
  • Transferring inside an exchange never touches the network; withdrawing does.
  • Being on a register is an obligation to enrol, not an approval.

Renato UlianovClosing · 39 s · in Portuguese

Educational material. The accounts and amounts in the figure are made up. Renato has a partnership with BYDFi, and the link on this page is a partner link: if you open an account through it, he is credited as the referrer. Nothing here is investment advice. No exchange is safe by decree — the choice and the risk belong to whoever deposits.