This experiment is exploring one of the approaches to allow TiddlyWiki to be able to save changes on any standards-compliant browser, without needing the browser-specific hacks that we've relied on in the past.

The approach here is to encode the data to be saved as a base64 data: URI, and then simulating a click on a link to that URI. By carefully crafting the link, most modern browsers can be forced to automatically download the data as a file in the default download directory. It works better on some browsers than others; notably only Google Chrome allows the filename of the downloaded file to be specified. Some browsers also give security warnings when the file is saved and/or reopened.

This means that the user experience goes something like this:

1. Load TiddlyWiki into the browser
2. Make changes and edits
3. Click the save command (or invoke it's keyboard shortcut)
4. The newly modified TiddlyWiki file will be downloaded to your downloads folder
5. Keep clicking save after each edit and each time a new copy of the file will be saved
6. Afterwards, the newest of the downloaded files will contain the latest content

It's really not a perfect experience, but it is very exciting that it works on more or less any browser.

Here is a summary of testing the demo on various browsers.

• The file is downloaded under the name Unknown (or Unknown-1, Unknown-2 etc if the file already exists)
• The first attempt to open the file causes OS X to display a warning dialogue about opening files downloaded from the Internet
• Once downloaded the file has to be manually renamed to have a .html extension before Safari will reopen it successfully

• Firefox displays a prompt to open or save the file
• The file is saved under a random name with the extension .part (for example IShr3ZJF(1).part)
• Firefox will happily reopen the file without renaming it, and without displaying a warning dialogue

• Chrome displays a prompt saying "This type of file can harm your computer. Do you want to keep SavedFile.html anyway?", and the user must manually click Keep
• The saved file is called SavedFile.html (or SaveFile (1).html, SavedFile (2).html etc if the file already exists). The string "SavedFile" is hardcoded into the demo
• Chrome will happily reopen the downloaded file without displaying a further warning dialogue

• Opera displays a prompt to open or save the file
• Choosing to save the file brings up another dialogue for the filename to be specified
• Opera will happily reopen the downloaded file without displaying a further warning dialogue

An adaptation of this technique can even work on iOS devices: on those devices it's possible to long click on the data: URI link and select to save it as a bookmark. Subsequently invoking that bookmark will reload the modified file.