Tiddlywiki
Tiddlywiki is a technological marvel if you are a technology nerd. It is a self contained wiki software in a single .html file with javascript. This means all the information, and all the code and UI are in the same file. You can add content and then save a new html file. This means you can carry this on a usb stick and open it on any browser that runs javascript. It's insane! Since it's javascript, you can modify the wiki on the fly. It's one of the most forward compatible and resilient pieces of software I have ever experienced. Even now I can open a 5 year old html file and have the entire website with fully functional search and a text editor in my browser. There are no external dependencies!
The link https://tiddlywiki.com/ is a instance of read-only tiddlywiki you can modify as you want, but the content is not updated on the web.
The experience
Tiddlywiki styles it self as a "a non-linear personal web notebook". Each note is a called tiddler, which I personally found disturbing. It uses wiki-style formatting, which I found slightly disturbing. There are no folders, you can search and pin tiddlers to the main screen and setup your system by yourself. A tiddler can be a text note, image or even self-executable javascript code. It can have arbitrary parameters and metadata and each tiddler can be a template for others so you are basically building your own system. You can link to any other tiddler using square rackets [[]] and it will automatically create it if it doesn't exist.
You can program various filters and queries to have a tiddler collect other tiddlers based on tags (For example, I had a tiddler collect all project tags and put them in a table, which updates dynamically as you add more)
The awesome
The tech!
It's hard to explain how cool it is to have the entire software in a single file which you can read, and modify as you wish. It's pure nerd cred if you are into it. It even allows hot reloading the changes. At any point you can modify the behavior of your notes and set everything exactly as you like (provided you are capable of reading the documentation and can code. I saw a lot of very successful projects (from D&D games, or entire books) and read-only project documentation (that you can self modify and explore as you wish) using TW. You can make interactive buttons, insert graphs and basically anything you can fit in a html canvas. You can then reuse those in other tiddlers so it's a self-building website.
The bad
The tech :(
Unfortunately, this amazing single file approach had some painful drawbacks which got worse as browsers got more secure. One issue is how to save the wiki once you update it. Right now (As of November 2023) you click save and it downloads a new file into your computer which you need to open again to have the latest info. There are various saver plugins or even custom web browsers that allow you to save the html file without having to download it, but that defeats the point of the file portability. So it is not as portable as claimed, since you need an electron app just to open and save it correctly. There is a hosted version and it's relatively easy to backup, but as a local first html-only file it's getting niche, and as a online-webapp it has to compete with a growing list of PKMs
Wiki syntax
I did not enjoy the wikipedia style syntax instead of markdown, because most notes were not easily readable/transferable without some parsing code.
Performance
Furthermore, the performance sadly does not scale. It can handle a solid (several hundred thousand) amount of entries, but a purely in-memory html file with javascript does bog down when you try to search that. Code living with notes is incredibly powerful concept I would love to explore, but from a purely pragmatic perspective it's not as performant as a well defined database.
The biggest consequence is system slowdown as you add more entries, especially images. Since the entire image is encoded in the single HTML file, it makes the filesize explode and it quickly becomes a huge memory hog. There is an alternative hosted mode (for the same tiddlywiki experience) using a node js server with a separate .tid (json) file for every entry and image which can lazy-load data on demand, but even that had problems with scaling to more notes.
(Though, to be fair, I hosted it on a pretty cheap instance.)
But as I added more things it just stopped being snappy, and I spent considerable amount of time just optimizing my setup (lazy-loading images, hosting a notebook server) because it got slower.
Mobile experience
The other main drawback is mobile experience. It's just.. not good. The hosted version is OK on the phone (though you can't upload images without javascript plugins), but writing experience was pretty bad and the UI wasn't very mobile friendly. It all works! But it's definitely not as slick. I did not enjoy doing any note taking from my phone, which was a huge killer for the whole thing.
Conclusion
I found tiddlywiki to be super exciting software which brought features that I still can't replicate in other software to this day. It's a philosophical marvel merging code and data in a single file and it really clicked with me as I either added more tiddlers or played with the system to make them more organized. Definitely addictive and fun for a tinkerer. However, I quickly found the system to bog down due to too many images which it was not handled to deal with. I also did not enjoy using it on my phone and I would not recommend it for users that are phone heavy.