What are the best productivity extensions for Chrome?

For students the useful set is narrower: something to capture text from slides and PDFs, something to manage citations, and something to stop you opening the same site forty times.

Zotero Connector is the citation answer and is free and open source. For capture, anything that reads text from the screen matters more than usual, because lecture slides, scanned readings, and locked-down course PDFs are all cases where you cannot select the text. Second Read handles those and keeps what you capture, which is free and has no student tier to worry about.

For focus, a blocker such as LeechBlock or Cold Turkey does more than any to-do extension. And Anki, though it is an app rather than an extension, is worth more than everything above put together if you have exams.

For reading and learning specifically, the extensions that matter are the ones that either remove distraction or bring material back to you later. Both are rarer than the category suggests.

Readwise, Matter, and Second Read all keep highlights, and they differ in what they do next: Readwise syncs to many other tools and emails a daily review, Matter is a reader with highlights attached, and Second Read captures anything on the screen including unselectable text and resurfaces one passage on every new tab. Choose on the second half, because the saving is equivalent and the returning is not.

For language learning, Toucan and Language Reactor are the two with a real method behind them rather than a word list.

Some do, noticeably, and most do not. The ones that cost you speed are those that run a content script on every page you open, which includes most ad blockers, grammar checkers, price comparers, and anything that scans page text continuously.

Extensions that only act when you invoke them, or that only replace a page you were going to open anyway, cost essentially nothing at rest. You can see the real numbers rather than guessing: Chrome has a task manager under the three-dot menu, More tools, Task Manager, which lists memory and CPU per extension.

The bigger cost is usually not speed. It is that every content script can read the pages you visit, which is worth spending on deliberately rather than by accumulation.

The number is not the problem; unused extensions are. An extension you have not consciously used in a month is pure cost, because it still runs, still has whatever permissions you granted, and still has to be trusted through every automatic update.

A good audit is twice a year. Open chrome://extensions, and for each one ask what it did for you this month and what permissions it holds. "Read and change all your data on all websites" is worth re-earning.

Extensions also change hands. A popular, well-behaved extension being sold to a new owner who quietly adds tracking is a recurring story rather than a hypothetical, and a periodic clear-out is the only practical defence.