# FAQ

### How to speed up PDF flipbook page loading?

For PDF flipbook, you can do couple of things to speed up the page loading.

#### PDF To Image Converter

Use [PDF to Image Converter](https://real3dflipbook.gitbook.io/jquery/optimized-pdf-flipbook) to convert PDF to images and JSON, then create image flipbook.

#### Optimize PDF for web

Typically, PDFs with a smaller file size will be rendered faster and it depends on how big a single page is. The amount of pages does not affect the performance. It's essential that you optimize your documents for the web. See [Optimize a PDF](https://helpx.adobe.com/acrobat/using/optimizing-pdfs-acrobat-pro.html) from Adobe's website for more information. There are more improvement techniques that we can suggest:

1. Avoid using high resolution images -- 150 dpi resolution for scanned images shall be enough for screens, especially for low powered devices;
2. Try to use JPEG encoding for color images/photos in RGB colorspace when possible;
3. Avoid using expensive compositions/effects such as transitions/masking -- flatten transparency;
4. Avoid using PDF generators (or don't create content) that produce ineffective PDF output (e.g. LibreOffice creates a lots of tiny images for vector elements/pictures it does not understand);
5. If there is such a setting, use web-optimized PDF output / linearization;
6. Fix or don't produce corrupted PDFs that do not conform to the PDF32000 specification.

### How to speed up image flipbook page loading?

1. Optimize images for web, by reducing the image quality to 60% - 80% which will bring down the size significantly but quality loss will be barely visible. This can be done with apps like Photoshop or with online tools 
2. Use WebP or JPEG instead of PNG.
3. Resize images, image height of 1500px - 2000px is enough for most cases. 

### Why flipbook is not working?

Please check your browser console for errors. In most cases the problem is that flipbook has no PDF/images specified, or is trying to load PDF/images from another domain. There might also be other javascript errors on the page.

### Can I load a PDF/images from another server (cross domain request)?

By default PDF and images needs to be on the same server. To use resources from another domain you need to add Access-Control-Allow-Origin header to server response, for example to allow [http://foo.example](http://foo.example/) to load the resources you need to add header

```
Access-Control-Allow-Origin: http://foo.example
```

### How to open flipbook lightbox from URL (at specific book page)?

Set custom deep linking prefix for flipbook, for example

```
deeplinkingPrefix: "book1_"
```

If your lightbox flipbook is at [http://example.com](http://example.com/) you can open flipbook at page 1 with [http://example.com#book1\_1](http://example.com/#book1_1) or at page 3 with [http://example.com#book1\_3](http://example.com/#book1_3)

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