Tumblr – How to Queue a Post for Next Year

MathJax is now available through a CDN, so you don't have to install it on a server any more. All you need to do is include a few lines in your html header and you can start using mathematics in your posts.

To do this, go to Theme -> Use custom HTML, and insert the following just above the </head> marker:

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js"></script>

Save changes, and you're ready to include mathematics on your Tumblr pages. Try, for example

\[ \exp(x) = \sum_{n=1}^{\infty} \frac{x^n}{n!} \]

Good luck, hope this helps.

Here's the official response from Tumblr support:

Beth, Nov-16 13:33 (EST): Hello,

If you are using a substantial number of tags on your posts, you may find that Tumblr doesn't show all of them in saved tags lists. The list may be shortened in order to ensure the pages where you create and edit posts load quickly.

You can still use as many tags as you wish. But, you will need to fully type out any tags that aren't displayed in the saved tags list. Our apologies for any inconvenience this might cause.

Please let us know if you have any other questions.

Thanks, Beth Tumblr Support support@tumblr.com

So it is expected behaviour, but no mention of what the hard limit is though.

Update from Renee in Tumblr support:

The hard limit for tag autocompletion is "closer to around 100 actually."