Lost hyperlinks, hyperlinks link to wrong place, hyperlinks stop working

Problem

Your presentation contains a lot of hyperlinks and suddenly you find that some of the links stop working. Either they link to the wrong place or don't work at all.

Solutions

There are several reasons why links stop working. Here are some things to check:

Commas in slide titles

If links to some slides don't work but links to others do, look for commas in the slide titles. Because of the way PowerPoint stores link information, commas confuse it and make the links break. Remove the commas from the slide title and all will be well.

Broken links in web pages made from PowerPoint

If your links take you unexpectedly to pages on the internet or cause PowerPoint to try to connect to the net, see Links between slides don't work in PowerPoint HTML

Too many links

Avoid creating presentations with too many links in the first place. Instead, create multiple linked presentations. See the linking tutorial at MVP TAJ Simmons' Awesome - PowerPoint Backgrounds.

Once links start to break, try deleting some of the slides that contain the broken links and/or break up the presentation into several smaller ones (see above).

Corrupted slides or links

It can also help to export the presentation to HTML then "round-trip" it back into PowerPoint by opening the resulting HTML.

Too many custom document properties/too much custom property data

Some add-ins store lots of data in custom document properties. These use the same limited storage area as links use; once that space is used up, links stop working. To view custom properties:

In PowerPoint 2007, choose Office Button | Prepare | Properties, then click the black down-arrow next to Document Properties in the pane that appears and choose Advanced Properties..., then click the Custom tab.

In PowerPoint 2003 or previous, choose File, Properties and click the Custom tab.

Look at the number and length of entries in the Properties list at the bottom of the dialog box. The more data is there, the less is available for storing links. Try deleting unneeded information.

Note that some add-ins may use this area to store information they need. If you see a lot of mysterious data there, check with your add-in vendor for updated versions. Suggest that they use slide or presentation tags rather than custom document properties. That will avoid this problem.

The Root of the Problem

According to this Microsoft article:

PowerPoint stores the hyperlink information in the Document Summary storage area of the presentation. This storage area has a limit of 64 KB. The Document Summary storage contains all the document properties, custom properties, references, and other similar data.

Because the Document Summary storage is used by different aspects of the presentation, there is a finite number of hyperlinks that can be stored in presentation. This is compounded by the fact that the longer the text is for a hyperlink that you have to store, the fewer you can store.

Theoretically you can store upward of 32 KB of characters in the Document Summary, which translates to approximately 6,500 words. More than half of this is already allocated to dedicated Document Summary items. After the free space is used, no more can be allocated to the presentation.

The reference to "words" is misleading. Word (to a human) might be something as short as "this" or as long as "http://deep.deeper.deepest.domain.com/folder/after/folder/after/folder/and/finally/ThisInsanelyLongFilenameThatsTotallyOverTheTop.htm?fFollowedByMilesOfQueryParametersThatOnlyASickoCouldLove"

Forget words. Count the characters, because it's the characters/bytes that count. And read the information above carefully: it starts by talking about 64k of available space but says that only half of that is dedicated to Document Summary, and then says that more than half of that is already allocated to other purposes.

That leaves us with 16k, or around 16,000 characters, of link storage. MAXIMUM. And some of that may be used up by custom document properties.

MS says that this problem no longer occurs with links you create to sites external to the presentation in PowerPoint 2002 and 2003.
MS acknowledges that it's still a problem for internal links.

The free PPTools FixLinks demo will give you a report on the links in your presentation and a general idea of how much space your existing links use. As a general rule, we'd suggest caution if it reports more than 15,000 bytes worth of links.

PowerPoint MVP Bill Dilworth has a clever workaround that relies on VBA but allows you to have an unlimited number of hyperlinks. See his Unlimited Links macro