Each extension must have a unique key. Extension keys can be alphanumeric and contain underscore characters. It may not start with a digit, the letter u, or the test_ prefix. However, not every combination of these symbols makes a good extension key.

An extension key must be descriptive but not too long. Having personal or company prefixes is not forbidden but is not recommended. Underscores should be avoided. Abbreviations should be avoided as well, because they often do not make sense for other users.

Examples of good extension keys are:

Examples of bad extension keys are:

Most TYPO3 extensions use a database to load and/or store their own data. Changing the data structure during application development...