If you use Firefox or Chrome browsers, you may have noticed that it’s been difficult to open digitised documents from our website. You may have had to wait a lot longer than normal for a file to open, or your files may not have opened at all.
What is going on?
Both the Firefox and Chrome browsers have switched to opening PDF files with their own dedicated PDF viewers. It turns out these viewers do not handle our digitised files very well.
What can be done about it?
One option is to use Internet Explorer when browsing our catalogue.
You could also make your Firefox or Chrome browsers use the standard Adobe PDF Reader to open PDF files. Instructions on setting the default PDF reader can be found for Firefox here and for Chrome here.
Do I have to use the Adobe PDF Reader?
Other dedicated PDF readers (e.g. Sumatra PDF) should work as well, it’s just the new Chrome and Firefox viewers that are having problems.
Want a more detailed explanation?
When we digitise paper documents we save them in PDF format, using a specific compression algorithm called ‘JPEG 2000′. This compression makes the files small enough to download easily, and produces a much better quality picture than the more widely used ‘JPEG’ algorithm.
Although ‘JPEG 2000′ is an open-source standard it is not as widely adopted as the older ‘JPEG’ algorithm (which is fine for most purposes, just not as good at compressing pictures of text). The PDF readers that Chrome and Firefox use as plugins do not appear to be as efficient opening ‘JPEG 2000′ encoded files. They can do it, it just takes longer for them to run through the maths that turns the numbers in the downloaded files into a picture on the screen.