TiddlyWiki ships with defaults that are designed to get the best out of modern devices from smartphones to desktop computers. If you need to work on older, less powerful devices, or work with large amounts of content, there are a few steps you can take to improve performance.
Avoid the "Recent" tab. It is computationally slow to generate and update in response to tiddler changes.
Use the "Vanilla" theme. The default "Snow White" theme includes visual effects like shadows, transparency and blurring that can be slow to render on older devices
Avoid large tiddlers. Large bitmaps can significantly slow TiddlyWiki's performance. For example, an image taken with a modern smartphone will often be 5MB or more. Use ExternalImages whenever possible
Don't have too many tiddlers open at once. Every tiddler you have open will require processing to keep it up to date as the store changes (for example, while you type into a draft tiddler). It is particularly easy when using zoomin story view to end up with dozens of tiddlers listed in the Open tab in the sidebar. Get into the habit of periodically closing all open tiddlers with the close all button
Keep in mind that transcluding separate tiddlers is more performant than heavy use of macros and the difference can be significant in some situations. The result of parsing each tiddler is cached and reused the next time if the tiddler has not changed. The same technique cannot be used for macros and they have to be re-parsed every time, as they are not global but local to the widget tree.
New in: 5.1.23 Parse trees are now cached for macros that do not perform any text substitution either via parameters or variables (i.e. $parameter$ or $(variable)$).
Where possible use the SetWidget or VarsWidget with filters instead of the WikifyWidget for declaring variables and string concatenation. The performance of the wikify mechanism is relatively poor as there is no opportunity to cache the parse tree or widget tree.