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Naming Conventions

The first thing you should decide on is the extension key for your extension and the vendor name. A significant part of the names below are based on the extension key.


Some of the names, such as extension key or vendor name, will be spelled differently, depending on where they are used, for example:

  • underscores (_) in the extension key are replaced by dashes (-), when used in the package name in the file composer.json (cool_shop -> cool-shop)

  • underscores in the extension key are removed by converting the extension key to UpperCamelCase in namespaces (cool_shop -> CoolShop)

Abbreviations & Glossary


UpperCamelCase begins with a capital letter and begins all subparts of a word with a capital letter. The rest of the word is in lowercase with no spaces, e.g. CoolShop.


lowerCamelCase is the same as UpperCamelCase, but begins with a lowercase letter.


= "TYPO3 extension repository": A catalogue of extensions where you can find information about extensions and where you can search and filter by TYPO3 version etc. Once registered on, you can login and register an extension key for your extension in > "My Extensions".


= extension key.


If the term ExtensionName is used, this means the extension key in UpperCamelCase. Example: extkey="bootstrap_package", ExtensionName="BootstrapPackage". The ExtensionName is used as first parameter in Extbase ExtensionUtility::configurePlugin or ExtensionUtility::registerModule().


= backend module key. There is a main module key and a submodule key.

Public extensions

Public extensions are publicly available. They are usually registered in TER and available via Packagist.

Private extensions

These are not published to the TER or Packagist.

Some of these "Conventions" are actually mandatory, meaning you will most likely run into problems if you do not adhere to them.

We very strongly recommend to always use these naming conventions. Hard requirements are emphasized by using the words MUST, etc. as specified in RFC 2119. SHOULD or MAY indicate a soft requirement: strongly recommended but will usually work, even if you do not follow the conventions.


If you study the naming conventions closely you will find that they are complicated due to varying rules derived from the extkey, if the extkey contains underscores. Sometimes the underscores are stripped off, sometimes not, sometimes a name in UpperCamelCase is created.

The best practice you can follow is to avoid using underscores in your extensions keys at all! That will make the rules simpler. This is highly encouraged.

Extension key (extkey)

The extension key (extkey) is used as is in:

  • directory name of extension in typo3conf/ext (or typo3/sysext for sytem extensions)

Derived names are:

  • package name in composer.json <vendorname>/<extkey>. Underscores (_) are replaced by dashes (-)

  • namespaces: Underscores in the extension key are removed by converting the extension key to UpperCamelCase in namespaces (cool_shop -> CoolShop).


If you plan to publish your extension, the extension key must be unique worldwide. This will be checked and enforced once you register the extension key on

The extkey is valid if the TER accepts it. This also makes sure that the name follows the rules and is unique.

Do this early!

  1. The extension key MUST be unique within your installation.

  2. The extkey MUST be made up of lowercase alphanumeric characters and underscores only and MUST start with a letter.

  3. More, see extension key

Examples for extkeys:
  • cool_shop

  • blog

Examples for names that are derived from the extkey:

Here, extkey is my_extension:

  • namespace: \Vendorname\MyExtension\...

  • package name in composer.json: vendorname/my-extension (the underscore is replaced by a dash)

Vendor name

The vendor name is used in:

  • namespaces

  • package name in composer.json, e.g. myvendor/cool-shop (all lowercase)


The vendor name MUST be unique (if you publish your extensions on packagist).

Register your vendor name early on Packagist!

Use common PHP naming conventions for vendor names in namespaces and check PSR-1. There are currently no strict rules, but commonly used vendor names begin with a capital letter, followed by all lowercase.

The vendor name (as well as the extkey) is spelled with all lowercase when used in the package name in the file composer.json

For the following examples, we assume:

  • the vendor name is Mycompany

  • the extkey is my_example

  • Namespace: \Mycompany\MyExample\ ...

  • package name (in composer.json): mycompany/my-example

See also

Database table name

These rules apply to public extensions, but should be followed nevertheless.

Database table names SHOULD be named:

"tx_" extkey (without underscores) "_" name

  • name: What does the table contain?

  • tx_coolshop_product

  • tx_coolshop_category

  • tx_coolshop_domain_model_tag

Extbase has the following naming convention for database models:

"tx_" extkey (without underscores) "_domain_model_" name

  • name: what does the table contain (use singular and same name as model)

Example for Extbase table name for the model "Post":
  • tx_blogexample_domain_model_post


You may notice, that the names above uses the singular, e.g. post and not posts. This is recommended, but not always followed.

Backend module key

The main module key SHOULD contain only lowercase characters. Do not use an underscore or dash.

The submodule key MUST be made up of alphanumeric characters only. It MAY contain underscores and MUST start with a letter.

  • Coolshop

Example usage:

// Module System > Backend Users
    // ExtensionName
    // Main module key (use existing main module 'web' here)
    // Submodule key
    // ...


Registered modules are added to $GLOBALS['TBE_MODULES']. TYPO3 may derive the full module signature from the extkey and modkey. Conversions, such as underscore to UpperCamelCase may be applied in this process.

You can look at existing module signatures in System > Configuration.

Plugin key

The plugin key is registered in:

  • second parameter in registerPlugin() (Extbase)

  • or in addPlugin() (for non Extbase plugins)

The same plugin key is then used in the following:

  • second parameter in configurePlugin() (Extbase): MUST match registered plugin key exactly

  • the plugin signature

  • in TypoScript, e.g. plugin.tx_myexample_myplugin

  • in TCA

  • etc.

The plugin key can be freely chosen by the extension author, but you SHOULD follow these conventions:

  • do not use underscore

  • use UpperCamelCase, e.g. InventoryList

  • use alphanumeric characters

For the plugin key, Pi1, Pi2 etc. are often used, but it can be named differently.

The plugin key used in registerPlugin() and configurePlugin() MUST match.

Plugin signature

The plugin signature is automatically created by TYPO3 from the extension key and plugin key.

For this, all underscores in extension key are omitted and all characters lowercased. The extkey and plugin key are separated by an underscore (_):


The plugin signature is used in:

  • the database field tt_content.list_type

  • when defining a FlexForm to be used for the plugin in addPiFlexFormValue()


Assume the following:

  • extkey is my_extension

  • plugin key is InventoryList

The derived name for the "plugin signature" is:

  • myextension_inventorylist This is used in tt_content.list_type and as first parameter of addPiFlexFormValue().

Class name

Class names SHOULD be in UpperCamelCase.

  • CodeCompletionController

  • AjaxController

See also

This follows PSR-1 conventions.


Extbase has some of its own conventions.

See also

Upgrade wizard identifier

You SHOULD use the following naming convention for the identifier:


This is not enforced.

Please see Wizard identifier in the Upgrade Wizard chapter for further explanations.

Note on "old" Extensions

Some the "classic" extensions from before the extension structure came about do not comply with these naming conventions. That is an exception made for backwards compatibility. The assignment of new keys from the TYPO3 Extension Repository will make sure that any of these old names are not accidentally reassigned to new extensions.

Furthermore, some of the classic plugins (tt_board, tt_guest etc) use the "user_" prefix for their classes as well.