Bitcoin Forum

So if you submit a transaction and it hasn't been confirmed yet, that means it's not on the blockchain right?
Does this mean that when you visit those block explorers (like blockchain.info etc) and you view the unconfirmed transaction, they are pulling the info from their node's mempool?

In a word... Yes.

This is why sometimes you can see your unconfirmed transaction on some blockexplorers and not others... because the blockexplorer that isn't showing your transaction does not have your transaction in it's mempool... (either not received or dropped etc)

Yes, they are pulling the info from their mempool, which is why it may be available on one site but not another.
When a bitcoin transaction is made, the transaction is broadcast to other nodes peered to it, then these nodes relay the transaction to other nodes etc until all nodes have it in their mempool.

yes,

blockexplorer s are using heavily modified bitcoin-core or custom implementation.,

all new tx are stored in mempool .aka. unconfirmed tx
so block explorer sites show you unconfirmed tx from their mempool.

when new block gets generated/mined, at the time of parsing, all the tx from mempool gets removed which are included/mined in the current block.

and so on.


 

You're correct. This is actually the main reason why you can view unconfirmed transactions on block explorers. The main reason why this happens is because of the mempool.