> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/core/get-started/faq/where-to-call-initialize.md).

# Where should I call the PDFNet initialize?

World's #1 PDF SDK Library for Web, Mobile, Server, Desktop

This is a very common question when using PDFNet for the first time. PDFNet `initialize` must be called before any other methods call with PDFNet.

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
pdftron.PDFNet.Initialize("YOUR APRYSE  LICENSE KEY::Testing::123");
```

{% endcode %}
{% endtab %}

{% tab title="C++" %}
{% code lineNumbers="true" %}

```cpp
PDFNet::Initialize("YOUR APRYSE  LICENSE KEY::Testing::123");
```

{% endcode %}
{% endtab %}

{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
PDFNet.initialize("YOUR APRYSE  LICENSE KEY::Testing::123");
```

{% endcode %}
{% endtab %}

{% tab title="JavaScript" %}
{% code lineNumbers="true" %}

```js
// Use runWithCleanup instead of initialize
// PDFNet initialize is called within runWithCleanup
// runWithCleanup will also perform automatic memory management
PDFNet.runWithCleanup(callback, "YOUR APRYSE  LICENSE KEY::Testing::123");

// Optional alternative to call initialize directly 
PDFNet.initialize("YOUR APRYSE  LICENSE KEY::Testing::123");
```

{% endcode %}
{% endtab %}

{% tab title="Obj-C" %}
{% code lineNumbers="true" %}

```objc
[PTPDFNet Initialize:@"YOUR APRYSE  LICENSE KEY::Testing::123"];
```

{% endcode %}
{% endtab %}

{% tab title="Swift" %}
{% code lineNumbers="true" %}

```swift
PTPDFNet.initialize("YOUR APRYSE  LICENSE KEY::Testing::123")
```

{% endcode %}
{% endtab %}

{% tab title="PHP" %}
{% code lineNumbers="true" %}

```php
PDFNet::Initialize("YOUR APRYSE  LICENSE KEY::Testing::123");
```

{% endcode %}
{% endtab %}

{% tab title="Python" %}
{% code lineNumbers="true" %}

```python
PDFNet.Initialize("YOUR APRYSE  LICENSE KEY::Testing::123")
```

{% endcode %}
{% endtab %}

{% tab title="Ruby" %}
{% code lineNumbers="true" %}

```ruby
PDFNet.Initialize("YOUR APRYSE  LICENSE KEY::Testing::123")
```

{% endcode %}
{% endtab %}
{% endtabs %}

The best location would be your application start-up function (such as `main()`, `OnAppStart()`, `DLLMain()`, etc. - depending on our application type and development platform).


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