In-depth blockchain explorer (III): Transactions

We've reached the halfway point of our guide, and it's time to delve into the core of the system: transactions. While previous chapters covered reading the block map and auditing addresses, this third installment will dissect the engine that drives each cryptocurrency across the network.

Mastering how to read a transaction on mempool.space is your best shield against uncertainty. Have you ever sent funds and then stared at your phone screen, praying they'd arrive? No more. From today onward, you'll know exactly where your money is in the process and what technical information the network is spewing out in real time.

The journey of a digital asset: From signature to block

When you perform a transaction, you don't "send" a file like an email. Instead, you sign a digital instruction that says, "I, the owner of these units, transfer them to this other address." This command travels to the mempool and waits for a miner to validate it.

In 2026, with the Bitcoin network more optimized than ever, explorers offer us complete transparency about this journey. By pasting your transaction ID (the famous TXID or hash) into the search engine, you'll find a detailed breakdown divided into key points:

• Confirmation Status: Does it appear in red or green? If it's red, your transaction is still in the waiting room. If it's green, it's already part of an immutable block.
• Inputs and Outputs: You'll see which direction the funds are coming from and where they're going. Be aware that this is where the "change direction" often appears—the return funds that go back to your wallet and can sometimes confuse beginners.
• Commission paid (Fee): You'll see how many sat/vB you've paid for and whether that amount is enough to enter the next block or if you've fallen short.

Why isn't my transaction moving?

This is the million-dollar question. Thanks to tools like mempool.space, you can see your actual position in the queue. If the network is congested and you've paid a low fee, you'll visually see how many megabytes of transactions you have ahead of you before a miner chooses you.

Knowing how to interpret this allows you to make proactive decisions, such as using functions of RBF (Replace-By-Fee) To raise the stakes and speed up the process if you're in a hurry. It's not magic, it's understanding the rules of the game.

Are you really going to keep relying on your wallet to tell you "pending" without knowing why? I prefer to see the actual data flow and understand if my transaction is competing with the rest of the network or if I've simply been too stingy with the fee.

In the following paragraphs, we'll break down how to read a transaction's dependency tree. Because sometimes, your submission isn't confirmed because it depends on another transaction that's still stuck. Welcome down the technical rabbit hole.

Bitcoin transactions

If you have followed our Bitcoin guideYou'll already know that every transaction on the network is permanently recorded on the blockchain. However, it's worth understanding the technical process of how a digital asset travels to avoid surprises when we look at our computer screens.

Imagine you want to send 0,5 BTC to a friend. The process isn't as simple as subtracting a number from a bank account. Your wallet has to search through the "pieces" of bitcoins you've previously received (the famous UTXO).

If your balance held 1 BTC, which you received in a single transaction, your wallet will use that entire block as input for the new transfer. The result will be two outputs: the 0,5 BTC your friend receives and another 0,5 BTC (minus the network fee) that is returned to one of your addresses as "change."

Much more than a balance transfer

As you can see, any transaction on the Bitcoin network is a much more complex exchange of information than it seems. It's not a simple "A gives money to B," but a data structure that you can audit in detail in mempool.space by entering the transaction ID (TXID).

Looking at an operation in the browser in 2026, the transparency is absolute. But what technical details can we actually extract from those torrents of code and graphics?

• The Hash or TXIDThe unique fingerprint of the transaction. Without this, you cannot claim or verify anything.
• Size and Weight (vBytes): Not all transactions take up the same amount of space. The more "pieces" of Bitcoin you use to make a transaction, the more space you occupy in the block and the higher the fee will be.
• Unlock script: The technical proof that you had the right to spend those funds.
• Timestamp: The exact moment a miner decided your transaction was valid and included it in the universal history of Bitcoin.

Did you really think your wallet only held a number? Every time you trade a cryptocurrency, you're moving pieces of a crypto puzzle. In the next section, we'll see how to identify if your transaction has been "stingy" with the fee and what the chances are of it being confirmed before you finish your coffee.

Have you ever stopped to think about why a €10 transaction can cost the same in fees as a €1 million transaction? The answer lies not in the value, but in the data.

Transactions in the block explorer

Following the usual methodology, we will use transactions present in the address that received the first block of the network or genesis block. In this case:

Address: 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa

Today, this address has accumulated thousands of transactions. Most are not commercial transactions, but symbolic sendings from users who, out of curiosity or respect, send a small fraction of their digital asset to "burn" a message into Bitcoin's history. Because the initial reward of 50 BTC is technically unspent, this address has become the most expensive and censorship-resistant bulletin board in the world.

What does mempool.space tell us about these transactions?

By entering this address into our browser's search engine, the panel offers us a fascinating snapshot of the community's behavior:

• The flow of "Dust": You'll see a huge number of tiny transactions. In the browser, these appear with fees sometimes higher than the amount sent, which shows that the goal isn't financial exchange, but rather data preservation.
• Messages in OP_RETURN: If you delve into the technical details of each token sent to this address, you'll find scripts containing text. It's the digital equivalent of carving your initials into a tree, only this "tree" is a global ledger distributed across thousands of nodes.
• Display filters: Thanks to the mempool.space interface, you can filter by confirmed transactions or see if there are any recent shipments waiting in the green mempool (the waiting area we saw in the previous chapter).

Have you noticed that, despite thousands of shipments, the "spendable" balance remains the same? That's the magic—and sometimes the frustration—of the original protocol rules.

Using this address as an example allows us to understand that a transaction is, in essence, a container of information. It not only carries value, but can also carry identity, messages, and proof of existence.

If your wallet shows a dull transaction history, take a look at this address on your computer. You'll see that every line in the browser represents a heartbeat of the network. Now that we know how to identify these historical transactions, how can we be sure ours won't be lost due to incorrect fee settings? Let's find out.

If we click on the link present in any transaction identifier, we will access the information page of a specific transaction. Let's look for example at the details of the first link.

As you can see, its appearance is the same as the pages described in previous articles, but with slight variations in the content shown. We are going to separate this information into sections in order to make a simpler and more understandable explanation of all the resources.

In the second column of information we can see the following summary of the transaction:

1. Total entries: number of bitcoins selected in order to successfully complete the transaction.
2. Total outputs: total entry minus transaction fees.
3. Mining rate- Bitcoin cents that vary based on the priority with which the issuer wants the transaction to be added to a new block.
4. Confirmation date: indicates the date and time the transaction was confirmed on the network.
5. Size: The size in bytes that the transaction occupies within a block.

After understanding all the parts that make up the transactions and how they are displayed in mempool.space, you are already in control of this block explorer.

FAQ – Block Explorer: Transactions