What is Perakun

Perakun is a Firefox extension that helps Japanese learners by providing dictionary lookups for mouseover text. A great feature is its ability to save lookups to a word list. This gif gives a good summary:

State of Perakun

As I mentioned previously, Chrome has taken the lion’s share of the browser market, and Firefox has plans to move to an addon subsystem based on WebExtensions, which will be compatible with Chrome.

Perakun exists as a legacy addon in Firefox for Japanese and Chinese, but only the Chinese WebExtensions addon exists in Chrome, with only a subset of the functionality.

In theory, an addon written in WebExtensions should plug and play in any supporting browser, but there is enough inconsistency in API support where the code will need some updating.

Rough plan of action

  1. Update the Chinese Perakun WebExtensions addon to be fully cross-browser compatible.
  2. Update the addon to support Japanese dictionary.
  3. Restore word list functionality missing from legacy addon.
  4. Add functionality to post to HiNative server for richer learning experience.


Currently, I’ve gotten started fixing up the WebExtensions addon, which you can find on github. I’ve made some simple replacements to some deprecated calls, but it still isn’t functional in Firefox.

Things I need to figure out still, are:

  1. document.caretRangeFromPoint has no equivalent function in Firefox but is being used in Chrome to get the mouseover text. It may be the case that the old way of doing it is still compatible and I will have to port it back in.
  2. Possibility of local SQLite database access? The old addon used Components to get read/write access to a SQLite dictionary packaged with the addon, but I’m not sure it’s possible with WebExtensions.
  3. Login/Session management? I’m pretty sure it’s possible to get user/password and login to HiNative with XHR and proper addon permissions.