A token trading on the name of a popular television series went from about $0.01 to over $2,861 in days. Coverage was everywhere. Buyers piled in.
The contract, on BNB Chain, carried a sell restriction presented as an anti-dump mechanism. To sell, you needed a second token. That second token was obtainable only through a platform that did not exist.
Buying worked perfectly. Selling did not work at all, for anyone except the developers.
On 1 November 2021 the creators pulled roughly $3.38M out of the liquidity pool and disappeared.
Here is why this is the autopsy for a lesson about explorers rather than a lesson about scams. The restriction was in the deployed contract the whole time. It was readable by anyone, for free, on a page that was one click away. The project's own documentation described it.
Every buyer was reading price. The price was real, in the narrow sense that trades were printing at it. It was also unrealisable, because the exit was closed in code.
Nobody was hacked. They were looking at the wrong screen.
The block explorer is the most useful tool in crypto and the one beginners avoid longest, because the first time you open one it looks like a wall of hexadecimal.
It is worth pushing through that, because everything else in this course has been describing a machine you could not see. This is the window.
What an explorer is
It is a website that reads the public chain and renders it in a browser. That is the entire product. It has no special access, no private feed, no privileged position. It runs nodes and formats the answers.
Which means two things worth holding onto.
The explorer is not authoritative. It is a view of the chain, not the chain. It can be behind, it can label things wrongly, and per F101-04 you are trusting it the way you trust any provider.
Anything it shows you, you could compute yourself. There is no gatekeeping here. The information was already public, and the explorer is reading glasses.
Reading a transaction page
Layouts change, so learn the fields rather than the furniture.
Status. Success or fail. Read this before anything else, and read the next section for why a failure still charged you.
Block and timestamp. Which block included it and when. The distance from the current block is your confirmation depth, which F101-02 taught you to convert into a cost rather than a count.
From and to. The signer, and the destination. If the destination is a contract rather than a person, you are looking at a call and not a payment.
Value. The chain's native asset moved, and this is the field that misleads most often. A value of zero does not mean nothing moved. Token transfers are not native value; they are state changes inside a contract, and they appear in a separate section.
Token transfers. The list of tokens that actually changed hands. On a swap, this is the truth of what happened, and it is where you confirm you received what you expected.
Gas. Limit, used, and price. Multiply to get what you paid.
Input data. The instruction itself. On a decoded call the explorer shows the function name and arguments in something readable. This is the same field F105 taught you to read before signing, and reading it after the fact on your own transactions is how you get fluent enough to read it before.
Gas is quoted in two parts and people conflate them constantly.
Gas used is a quantity of computational work. A plain transfer is 21,000 units, fixed by the protocol. A token transfer is typically 45,000 to 65,000. A complex swap can be 150,000 to 300,000 or more.
Gas price is what you paid per unit, quoted in gwei, where 1 gwei is 0.000000001 ETH.
Take a token transfer using 52,000 gas at 25 gwei:
52,000 x 25 = 1,300,000 gwei
Convert to ETH:
1,300,000 / 1,000,000,000 = 0.0013 ETH
At an ETH price of $3,000:
0.0013 x $3,000 = $3.90
Now the fact that changes behaviour. Notice that nothing in that calculation refers to the amount you sent. Moving $10 and moving $10,000 in the same token cost the identical $3.90, because you are paying for computation, not for value.
Which produces a real rule: fee as a share of the amount collapses as the amount grows. On this example, $3.90 is 39 percent of a $10 transfer and 0.039 percent of a $10,000 one. If you are moving small amounts on an expensive chain, the fee is the dominant cost of the whole activity, and that is the arithmetic behind every "use a cheaper chain for small transfers" recommendation you will hear.
Failed transactions cost money
This surprises everyone once, and understanding why teaches you what the network is actually selling.
The network executed your instruction. Partway through, something made it impossible to complete: slippage moved, an approval was missing, a condition in the contract rejected it. The state change is reverted, so nothing moved.
The computation still happened. Validators performed the work, and you pay for work, not for outcomes.
A failure is also information rather than just a cost. It usually means a condition you did not know about was checked and not met, which is worth understanding before you retry with a higher gas limit and fail again more expensively.
Explorers show a badge on contracts whose source code has been published and checked against what is deployed.
It certifies exactly one thing: the published source compiles to the deployed bytecode. You are looking at the real code.
It does not certify that the code is safe, that it does what its name suggests, that it has been audited, that the developers are honest, or that you will be able to sell.
SQUID's restriction was in verified, readable, published source. Verification worked exactly as designed and told everybody the truth, which was that the code preventing them selling was genuinely the code that was running.
The three questions before you buy anything
This is the practical payoff, and it takes about five minutes on the explorer's token page.
One. Who holds the supply? Open the holders list. If a handful of addresses hold most of it, everything about the price depends on what those addresses do. Treat this as raising a question rather than answering one, because supply legitimately sits in treasuries, vesting contracts and exchange wallets, and it can also be split across many addresses by one party specifically to look distributed. S202 turns this into a real method.
Two. Can I sell? Look for sell transactions in the recent history from addresses that are not the deployer. If everything is buys, ask why. Then read the contract for anything gating transfers: a required second token, a whitelist, a fee that is prohibitive on sells, a pause function. This is the question SQUID's buyers did not ask, and it was answerable.
Three. Who controls the contract? Is there an owner address? Can it mint, pause, change fees, or upgrade? An upgradable contract means today's code is a statement about today.
None of these require you to read code fluently. All three are visible on a page you can reach in one click, for free, before you spend anything.
If the price is real and rising, the token is at least tradeable.
Price and exit are two different facts, and SQUID is the cleanest demonstration ever produced.
A quoted price means a trade printed at that level. It says nothing about whether you can transact at it. Between you and that price sit questions the number cannot answer: is there liquidity at any depth, would your size move it, and is selling permitted by the code at all.
SQUID quoted over $2,861. Trades were genuinely occurring. And the realisable value for a normal holder was zero, because the contract required a token that did not exist.
Any market capitalisation calculated from that price was arithmetic performed on a number that did not describe anything, which is a habit worth breaking generally: market cap is price multiplied by supply, and if the price is unrealisable then so is everything derived from it.
Build the habit
The lab for this course, F101-L, is exactly this: trace a simple transfer, a token swap, and a failed transaction end to end, and explain in writing why the failed one failed and where the gas went.
Do it on your own transactions first. The screen looks impenetrable for about a week and then it organises itself, and after that you stop trusting interfaces and start verifying. That shift is the actual outcome of this whole course.
The chain was always public. The explorer is just how you look.
An explorer is a window onto a chain that was already public, and it is not authoritative, so read the fields rather than trusting the labels: status first, then token transfers rather than the value field, then gas used times gas price, which does not depend on the amount you sent. Failed transactions cost money because you pay for computation and not for outcomes. A verified badge certifies only that the published source matches the deployed bytecode, which is exactly why it told the truth about SQUID's sell restriction while $3.38M was lost. Before buying anything, spend five minutes answering three questions: who holds the supply, can I sell, and who controls the contract.