Link Whisper was built to be very light-weight and low impact on your user-facing pages. Nearly all of Link Whisper’s processes take place inside the WordPress Admin, so there’s very little to slow page load speeds.
Also, Link Whisper only inserts permanent links into your posts. This means that your site doesn’t have to process any special code to display the links you insert. So your pages won’t experience any special slowdowns from adding links.
Our friends at Authority Hacker created a review of Link Whisper. They found that having it active did not slow down their testing site. If you want to see what they had to say, you can watch the review here. The link will start the video at the speed testing section.