Write on Bitcoin's Blockchain with OP_RETURN

What is OP_RETURN?

It is a Bitcoin transaction's field that allows you to write a string of 80 byte (Bitcoin Wiki); in other words, you can write a sequence of 80 characters, that these will be linked forever in a Bitcoin's transaction.
You can read the full story to this link.

OP_RETURN in a transaction [Explained]

This is a Bitcoin's transaction:

{
   "hash":"b6abffe30b0edef88c796d0a21118046874b55c9c3b98adfb17aa6d9699e679d",
   ...
   "block_height":328455,
   "inputs":[
      { ... }
   ],
   "out":[
      { ... },
      {
         "type":0,
         "spent":false,
         "value":0,
         "n":2,
         "tx_index":5538187677742287,
         "script":"6a26492063616e74207365652075206275742049207374696c6c206c6f766520796f75206c696c69"
      }
   ]
}

Let's focus on out section (output of the transaction), particularly on script section.
We could have more script fields, but the value of OP_RETURNis that sequence of alphanumeric values preceded by characters "6a".
In this case it is:

26492063616e74207365652075206275742049207374696c6c206c6f766520796f75206c696c69

The OP_RETURN's value is in hexadecimal, so we have to translate it in "human language".
We can use this online tool.
The result of this conversion will be:

I cant see u but I still love you lili

Run 'OP_RETURN' message tracking tool

Installation

git clone https://github.com/merendamattia/op-return-tracking-message-bitcoin.git

Configuration

Insert in the hash.txt file the transaction hashes of the messages you want to trace, each on a different line.

The algorithm ignores any line that includes characters other than alphanumeric ones.
The - character placed as the first character of the line denotes the line as a comment.

Execution

Open the index.html file in your browser.

How do I write the OP_RETURN in a transaction?

I currently use the "imToken" mobile application, which allows you to populate the OP_RETURN field when sending a transaction.

Live demo

On my website: https://www.merendamattia.com/dev/btc/tracking/