Since November 2016 it is possible to create FlippingBook publications in HTML instead of Flash. Despite the many advantages of HTML5, there is a small downside: the size of the generated output is generally bigger. This is no problem if you use FlippingBook Cloud, but can be a concern if you upload to your own server. Depending on your imported file the difference can even be huge. In this article, we explain what causes this and what you can do to reduce publication size.
What causes the flipbook size to be so much bigger than my PDF?
Our HTML5 format requires us to make 'image' files of all your pages. Image files are very inefficient compared to normal text which is used in your PDF. When using normal text, a full page of A4 is just 5KB in size. But a high-quality image of the same page is at least 200KB, 40 times more. So it's not that strange if your 10MB PDF book (which is mostly text) turns out much larger when published as a FlippingBook.
A second reason that the FlippingBook is bigger than the PDF is that there are several copies of each page: for normal viewing, for zoomed viewing, and for download.
How does the size affect your readers?
End users (the people who look at your FlippingBooks) will not notice much, if anything at all. As said, your flipbook consists of several different images for every page. But we only load the images that your users need, at the moment that they actually need them. So most of these pages are never loaded at all by most users. And the pages that are loaded, are loaded bit-by-bit.
What you can do to reduce publication size?
The first question to ask is ‘Do I need to do anything at all’? If your server has more than enough space, then uploading the larger flipbook will not affect your server negatively. Also, if your publication almost exclusively consists of text, then none of the tips will make a big difference. But if you have a mixture of text and images then to reduce size you can:
- Disable downloads: by default, we allow users to download the original PDF and single pages that we create separately. You can disable ‘current page’ downloads and/or ‘full publication’ download. You can configure download options in Controls tab, by clicking on the button Customize next to the options Print and Downloads:
- If you don't want to sacrifice the download option, then we suggest to at least optimize your PDF before you import it. This can be done in Adobe Acrobat Pro, where you can save your PDF as a reduced size PDF.
- Reconvert with lower quality: apart from downloads, the most space is taken by the graphics. You can reduce the quality of the ‘Page Substrate Layers’, which contain the graphical elements. In most cases the difference will be barely noticeable to your readers, even if you reduce it to minimal quality. If space reduction is important to you, then don’t be afraid to experiment with this setting.To reconvert pages:
- Go to the Pages tab, and press Ctrl+a to select all Pages
- Right click on any page, select Import -> Reconvert selected pages
- Click on the small cogwheel button and go to the Desktop HTML5 tab
- Reduce the sliders for Normal Page Substrate layer and Zoomed Page Substrate Layer
How much space can you save?
How much space you save depends very much on your source PDF. For example, the size of the PDF that we used ‘Through the looking Glass’ example was 3MB. The final publication to upload was 107 MB. By applying the tips above, there was a modest reduction to 78MB.
On the other hand, the original PDF for our our 'Kawasaki' brochure was 21 MB. The first attempt after we published it was 91MB. This was reduced to 68MB after we optimized the PDF, and even to 32 MB when we removed downloads and reconverted with lower quality settings! A third of the original size and barely more than the PDF itself