The approach is the following: 1) Open an interesting webpage in your target language. 2) Select text. 3) The extension replaces some words with gaps. 4) Read the text, fill in the gaps. Obviously just typing random words out of the blue can be overwhelming, so there is a mode to drag&drop words from a list into the correct places.

I personally see this as active reading. My brain not only consumes information, but always try to guess the word from the context. I suspect that this helps with active vocabulary (i.e. to actually use the new words in writing). In the end I passed C1 exam (obviously I did other preparations too, not only this extension).

This is a beta version for now and it is 100% free:

Chrome: https://chrome.google.com/webstore/detail/vocabboost/obgbcamdmcdcenchjmhggocjabmnnaab

Firefox: https://addons.mozilla.org/en-US/firefox/addon/vocabboost/

If you didn't enjoy my explanation skills, there is an example video here: https://vocab-boost.online/

I would love to hear whether you find this useful and your ideas how I could improve it.

I might add payed features eventually to help developing the extension further, but I don't know a good mechanism to do this. I understand that 1$ in the US is very different from 1$ in e.g. India. I want this extension to bring value to everyone independently of their location and financial state. My current plan is to have the base version (i.e. like now) always free, since this already provides majority of value. Curious to hear your thoughts.