---
title: "Creating a new extension from scratch"
manual: "TYPO3 Explained"
version: "main"
permalink: "https://docs.typo3.org/permalink/t3coreapi:extension-create-new@main"
source: "ExtensionArchitecture/Kickstarter/FromScratch/Index.rst"
modified: "2026-09-16T13:05:25+00:00"
---

# Creating a new extension from scratch

First choose a unique [Composer name](https://getcomposer.org/doc/04-schema.md#name)
and an extension key for your extension.

If you plan to publish your extension in the TYPO3 Extension Repository
(TER), [register an extension key](https://docs.typo3.org/permalink/t3coreapi:extension-key@main).

> [!NOTE]
> **See also**
>
> There are different ways to kickstart an extension.
> See [Extension kickstarters](https://docs.typo3.org/permalink/t3coreapi:extension-kickstart@main).

-   Create a directory with the extension name
-   Create the [composer.json](https://docs.typo3.org/permalink/t3coreapi:files-composer-json@main) file

## Installing the newly created extension

Since TYPO3 v11 extensions can only be installed
using Composer as part of a Composer-based installation.

However, during development you should test your extension locally
before publishing it. Create the extension directory in the
`packages` directory inside the TYPO3 project root directory.

Then edit your project's [`composer.json`](../../FileStructure/ComposerJson.md#file-extension-composer-json) (The one in the TYPO3 root
directory, **not the one in the extension**) and add the following repository:

**composer.json (excerpt)**

```json
{
    "repositories": [
        {
            "type": "path",
            "url": "packages/*"
        }
    ]
}

```

After that install your extension via Composer:

```bash
composer req my-vendor/my-extension:"@dev"
```

> [!TIP]
> **Hint**
>
> In Classic mode installations put the extension in the
> `typo3conf/ext` directory and then **activate** it in
> **System > Extensions**.