user84128: So I have a wallet with thousands of addresses, I want to know how can I check the blockchain whether or not a transaction has been made to one(or another) of the addresses?

user26873: There are several API services that allow bulk address queries.
For example smartbit's API takes up to 1,000 addresses with their v1/blockchain/addresses endpoint which will return details about each address sorting by the highest balance first.
Example GET request:
https://api.smartbit.com.au/v1/blockchain/addresses/1DuMuchPBGNoi5b9JmpreZ2L5EpuMiJdyc,1N75aWck3TFPorTvSgdzLUttY8uddqTAFZ,161UqtBktXJMzcg2zxBGMiHgnVrtH78Amx,19eK34996XoXPgpranrUVSPLmkxzowt8ox
Link to API docs: https://www.smartbit.com.au/api
EDIT: Smartbit API is permanently offline
EDIT 2: Blockcypher offers a similar API service.
https://www.blockcypher.com/dev/bitcoin/#address-balance-endpoint

84128: <p>So I have a wallet with thousands of addresses, I want to know how can I check the blockchain whether or not a transaction has been made to one(or another) of the addresses?</p>
 26873: <p>There are several API services that allow bulk address queries.</p>
<p>For example smartbit's API takes up to 1,000 addresses with their <code>v1/blockchain/addresses</code> endpoint which will return details about each address sorting by the highest balance first.</p>
<p>Example GET request:<br />
<a href="https://api.smartbit.com.au/v1/blockchain/addresses/1DuMuchPBGNoi5b9JmpreZ2L5EpuMiJdyc,1N75aWck3TFPorTvSgdzLUttY8uddqTAFZ,161UqtBktXJMzcg2zxBGMiHgnVrtH78Amx,19eK34996XoXPgpranrUVSPLmkxzowt8ox" rel="nofollow noreferrer">https://api.smartbit.com.au/v1/blockchain/addresses/1DuMuchPBGNoi5b9JmpreZ2L5EpuMiJdyc,1N75aWck3TFPorTvSgdzLUttY8uddqTAFZ,161UqtBktXJMzcg2zxBGMiHgnVrtH78Amx,19eK34996XoXPgpranrUVSPLmkxzowt8ox</a></p>
<p>Link to API docs: <a href="https://www.smartbit.com.au/api" rel="nofollow noreferrer">https://www.smartbit.com.au/api</a></p>
<p>EDIT: Smartbit API is permanently offline</p>
<p>EDIT 2: Blockcypher offers a similar API service.</p>
<p><a href="https://www.blockcypher.com/dev/bitcoin/#address-balance-endpoint" rel="nofollow noreferrer">https://www.blockcypher.com/dev/bitcoin/#address-balance-endpoint</a></p>
