Understanding Bitcoin Blockchain Blocks when Looking at Blockchain.info

When you first hear the terms bitcoin, blockchain, blocks and mining, you may get confused. This article will explain to you what the terms associated with blockchain blocks mean using the website that updates the information about blockchain in real time because it is much easier to understand a theory when you are looking at its practical applications. This website is blockchain.info/data.

When you visit the website, on the “data” page you will see a table with the fields “Height,” “Age,” “Transactions,” “Total Sent,” “Relayed By,” “Size” and “Weight.”

Bitcoin is a completely transparent network. This means that the network contains information about all the transactions that have occurred on the network since its inception in 2009.

You can see the genesis block by typing “0” in the search field of the website blockchain.info. Here is a direct link to the genesis block: https://blockchain.info/block/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

That block was created on January 3, 2009 (this is the timestamp date and received date). This day is considered to be the birthday of the network. The block contains only 1 transaction, which is 50 coins awarded to the creator of the block as an award for mining the block.

Mining is the process during which members of the bitcoin network combine transactions into blocks. Miners do so because they get awards in the form of a bounty for mining a block and fees from the transactions included in the block. First blocks of the blockchain included no transactions other than the bounty for mining the blocks, which is why you will see that “estimated transaction volume” field is equal to zero and “transaction fees” are also equal to zero.

You can see that there was only 1 transaction in the “number of transaction” field for the block. An output is a number that shows how many bitcoins have been sent out. That’s what the “output total” field shows. For the genesis block, this number is 50, the number of bitcoins that the miner of the block received as an award. There have been no other transactions.

The term “height” describes the distance between the block and the genesis block. For the block #0, the height is 0. The first block you see on top of the table at https://blockchain.info/ is the latest block that has been added to the blockchain. For example, if the height of the block is 494514, it means that the total number of blocks in the blockchain when this block was added equaled to 494514.

The first transaction on the bitcoin network occurred in block 170. Here is a direct link to the block: https://blockchain.info/block/00000000d1145790a8694403d4063f323d499e655c83426834d4ce2f8dd4a2ee

This block shows the transaction during which Satoshi Nakamoto has sent a payment to Hal Finney. This happened on January 12, 2009.

The number of transactions is much larger for some of the recent blocks. For example, block #494514 has 1989 transactions with a total output of 12,807.56205803 BTC. This is what the numbers in the fields “transactions” and “total sent” show.

Field “age” shows the age of the block. For example, “age” of 26 minutes means that a block was generated 26 minutes ago. One of the goals of the bitcoin network is to generate a block every 10 minutes. The network adjusts the speed of block generation depending on how many miners are currently generating blocks by increasing or decreasing “difficulty,” which is why the time isn’t always 10 minutes. For example, when looking at the “age” column on the data page, you may see a sequence of numbers such as 10 minutes, 13 minutes, 25 minutes. This means that it took the network 10 minutes to generate the first block, 3 minutes to generate the second block and 12 minutes to generate the third block.


Because the bitcoin network is totally transparent, you can see “difficulty” on the pages for all individual blocks.

Today the mining of the blocks requires a lot of computer power. For this reason, many miners join together and create mining pools. The field “Relayed By” indicates the mining pool that mined the block. After a pool mines a block, it receives an award for doing so and it also receives fees from the transactions that it included in the block. Originally, transactions did not include any fees. Lately, this has been changing. Miners can choose which transactions they include into the blocks they mine, which is why they obviously prefer transactions where the sender included a fee.

The field “size” means the size of a blockchain block. Historically, a typical size of a block has been around 1 MB. The issue with this size is that a block of such size that only include so many transactions, which is why as of November 2017, the concept of “size” is being replaced with the concept of “max block weight.“ In November 2017, max block weight was 4MB.

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