A blockchain is a public ledger of transactions. Whenever someone sends Bitcoin or another cryptocurrency from one wallet to another, the transaction is recorded on the ledger.
But how does anyone view the transaction? The simplest way is by using something called a block explorer.
What Is a Block Explorer?
A cryptocurrency block explorer is an online blockchain browser that can show the details of all transactions that have ever happened on a blockchain network.
There are block explorers for Bitcoin and also for individual altcoins. Some block explorers can be used on multiple different networks, while others are only for one specific blockchain. A BTC block explorer, for example, would only be able to find information from the Bitcoin network, such as when someone is sending Bitcoin to another wallet.
A block explorer can be used to find any specific transaction or view the recent history of the chain more generally.
What Can You Do With a Blockchain Explorer?
A blockchain explorer allows users to view blockchain activity. Users might use block explorers to track the status of a pending transaction (technically referred to as exploring Mempool status, since the transaction has not yet been recorded in a block and added to the chain) or to view the balance of a wallet they hold without having to use the crypto wallet itself.
Beyond these types of tasks, block explorers can also be used to:
• Examine the history of any wallet address, including all transactions sent to and from that address.
• Explore change addresses, which are transaction outputs that return coins to the spender in an effort to prevent too much of the input value being spent on transaction fees.
• View blocks that aren’t attached to the main blockchain and whose parent blockchain is unknown. These are called “orphaned blocks.”
• Explore the largest transaction that was sent in the last 24 hours.
• Explore the number of double-spend transactions happening in a blockchain.
• Discover the individual or mining pool who mined a specific block.
• Explore the genesis block, or the first block that was ever mined on a given chain.
• See other information specific to a blockchain, such as average transaction fees, hash rate, mining difficulty, and other data.
There are also more advanced use cases for block explorers, but these are mostly utilized by companies that create sophisticated software to track criminal activity or try to predict cryptocurrency prices.
How Do Blockchain Explorers Work?
An explorer is basically a blockchain search engine. It can be used to search for just about any information pertaining to the state of a specific blockchain that someone might want to know. The details of every crypto wallet and all of its transactions and more can all be found using a blockchain explorer.
Before we get into the step-by-step of this process, there are a few key terms worth knowing.
• Rational Database: Allows for the storage of data in a table in terms of how each piece of data is related to others. Rather than having one giant block table with all details for each block, entries can be organized according to their type and relation to similar entries, for example.
• Structured Query Language (SQL): A protocol for searching a database, or giving a query. Software of this nature can create a table in a database, insert records into that table, search for a given term, then create a new table with relevant results and present them on a web page.
• Application Programming Interface (API): A protocol that makes it possible for users to communicate with computers through software. APIs define the formatting details for responses that are sent and received by the software being used.
How a Blockchain Explorer Works, Step by Step
From a technical perspective, here’s what it looks like:
1. Blockchain explorers use application programming interfaces (APIs), rational databases, and SQL databases alongside a blockchain node to retrieve information from a network.
2. The software organizes this information into a database and displays things in a searchable format.
3. The explorer can then be used to perform searches through an organized table in response to user demands through a simple user interface (think: search engine) that allows people to conduct searches.
4. The explorer server creates a web page through which it can interact with users.
5. An API also allows the explorer to interface with other computers.
6. Search requests are sent to the backend server, which then responds to the user interface.
7. Finally, the user interface and API sends web pages in HTML format to the user’s browser so the results can be read in a manner that is easy to understand.
Examples of Blockchain Explorers
What follows are some of the most popular blockchain explorers. There are different explorers for different types of cryptocurrency, though some explorers can be used to search multiple chains.
Blockchain.org, formerly known as Blockchain.com, is a popular Bitcoin block explorer. It allows users to search the Bitcoin blockchain by transaction, address, or block. Many Bitcoin users have probably used Blockchain.org at some point to monitor or record their Bitcoin transactions.
While most block explorers work on only one blockchain, Blockchair can be used to search multiple chains. This explorer allows for searches on the Ethereum, Bitcoin Cash, and Bitcoin blockchains. Users can look up words, mining difficulty, Mempool size, and nodes.
Tokenview also allows for searches to be conducted on multiple blockchains — more than 20 of them, in fact. This explorer is based in China and was launched in 2018.
A block explorer can be thought of as a search engine for a blockchain — allowing a user to find lots of different information about that blockchain.
To use a block explorer, you simply visit its website and enter the information you’re looking for. To look up a pending transaction currently stored in the Mempool, for example, you could enter the transaction hash ID provided by your wallet or exchange.
Or, those curious about blockchain technology could just use the block explorer to “explore” the blockchain in general and look at things like the largest transactions, the most recently mined block, or hash rate.
Photo credit: iStock/solidcolours
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