Tiddlywiki ir personīgs wiki un nelineārs piezīmju grāmatiņa sarežģītas informācijas organizēšanai un apmaiņai. Tā ir atvērtā avota vienas lapas lietojumprogramma wiki viena HTML faila formā, kurā ietilpst CSS, JavaScript un saturs. Tas ir paredzēts, lai būtu viegli pielāgojams un atkārtoti formēts atkarībā no pielietojuma. Tas atvieglo satura atkārtotu izmantošanu, sadalot to mazos gabaliņos, ko sauc par Tiddlers.

TiddlyWiki is designed for customization and to be shaped according to users’ specific needs, perhaps comparable to a high-end programming language. As such, it can be shaped into a wide and arbitrary range of special applications. Examples include niche note taking applications, to-do lists, presentations, collections, authoring tools, personal databases, recipe collections, etc.

Although there are many TiddlyWiki documents on the Web, the majority of TiddlyWikis reside on personal computers or in the cloud, or are exchanged over email, in a manner similar to word processing documents and spreadsheets. As a single HTML file, or saved as an HTA file in Microsoft Windows (allowing corporate IE lockdown to be bypassed), TiddlyWiki can be useful in corporate environments where red tape or IT resources might prevent the use of a wiki that requires a more complicated installation.