user4822: There is a service provided by blockchain.info described on json_rpc_api page.
More or less it describes the API that user can use to access their blockchain similar way as using bitcoin-cli to own daemon.
It usage is currently demonstrated as:
$ ./bitcoin-cli -rpcconnect=rpc.blockchain.info -rpcport=443 -rpcssl -rpcuser=YourWalletIdentifier -rpcpassword=YourPassword getinfo

It looks nice but there is an information on the site which states:

From the 1st December 2014, in order to use this API, access must be explicitly enabled, and all client ip addresses whitelisted by the wallet owner. Manage access in [Account Settings] -> [IP Restrictions] 

And that's the problem, because I'm interested just into fetching some block or transaction details. I don't need any RPC which would require authorization. I don't even want to create an account.
So the question is:
Are there any free services (or maybe it is still available on blockchain.info somehow?) which allows to use JSON-RPC against their bitcoin daemon?
I don't care about the speed or waiting 10 seconds between each call etc.

user75032: There is a free bitcoin-cli sandbox at bitcoindev.network:

Here is a simple sandbox environment for trying out the bitcoin command line interface! Select Start Scenario to bootstrap your own private instance! 

You can check out the on-line sandbox here:
https://bitcoindev.network/bitcoin-cli-sandbox/
Simultaneously they provide a docker container for it, so your students can go up & running with their own daemon in a blink of an eye.

4822: <p>There is a service provided by blockchain.info described on <a href="https://blockchain.info/api/json_rpc_api" rel="noreferrer">json_rpc_api page</a>.<br>
More or less it describes the API that user can use to access their blockchain similar way as using bitcoin-cli to own daemon.<br>
It usage is currently demonstrated as:</p>

<pre><code>$ ./bitcoin-cli -rpcconnect=rpc.blockchain.info -rpcport=443 -rpcssl -rpcuser=YourWalletIdentifier -rpcpassword=YourPassword getinfo
</code></pre>

<p>It looks nice but there is an information on the site which states:</p>

<blockquote>
  <p>From the 1st December 2014, in order to use this API, access must be explicitly enabled, and all client ip addresses whitelisted by the wallet owner. Manage access in [Account Settings] -> [IP Restrictions] </p>
</blockquote>

<p>And that's the problem, because I'm interested just into fetching some block or transaction details. I don't need any RPC which would require authorization. I don't even want to create an account.<br>
So the question is:<br>
<strong>Are there any free services (or maybe it is still available on blockchain.info somehow?) which allows to use JSON-RPC against their bitcoin daemon?</strong><br>
I don't care about the speed or waiting 10 seconds between each call etc.</p>
 75032: <p>There is a free bitcoin-cli sandbox at bitcoindev.network:</p>

<blockquote>
  <p>Here is a simple sandbox environment for trying out the bitcoin command line interface! Select Start Scenario to bootstrap your own private instance! </p>
</blockquote>

<p>You can check out the on-line sandbox here:</p>

<p><a href="https://bitcoindev.network/bitcoin-cli-sandbox/" rel="nofollow noreferrer">https://bitcoindev.network/bitcoin-cli-sandbox/</a></p>

<p>Simultaneously they provide a docker container for it, so your students can go up &amp; running with their own daemon in a blink of an eye.</p>
