Let's imagine the following scenario: you have a large, well-tuned eZ Publish project that you have been maintaining for years. All of the sudden, the client informs you that they want to upgrade it to the latest eZ Platform version so they could use all the new fancy stuff they've heard of. The only problem is, your trusted project depends on several custom legacy datatypes. This workshop will demonstrate how you can easily rewrite all your custom datatypes to new eZ field types and use them for reading and writing in the new stack. For this purpose, we will reverse-engineer the legacy eZ Tags datatype and provide you with a step-by-step tutorial on how to rewrite it to the eZ Platform field type.