## How does getblocktemplate select transactions?

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I wrote a script that compares the transactions listed in the memory pool with the transactions included in getblocktemplate:

http://learnmeabitcoin.com/explorer/node/memorypool

(I've ordered the transactions by [current priority], and highlighted the ones included in getblocktemplate in blue.)

• How does getblocktemplate choose which transactions to include from the memory pool in a candidate block?

• Why aren't transactions being selected from highest to lowest priority?

The whole mempool won't fit in a block; getblocktemplate returns enough transactions for a block. Blocks are, by default, limited to 750kb by policy, but many miners increase the size to the block limit of 1mb (which can be done by command-line flag).