Speedifier is a Mac app that lets you control video speed in Safari for HTML5 videos. You can use the extension on any website. Speedifier was developed by Arno Appenzeller, a part-time Mac and iOS indie developer from Germany.
Controlling Video Playback
Speedifier is really a Safari extension, but Arno decided to package it as an app so he could sell it on the Mac App Store. It costs US$1.99, which is a steal considering what it can do for you. After installing the app, open Safari > Preferences > Extensions to enable the extension.
There are three speeds to choose from:
- Slower: -0.25x
- Normal: 1.0x
- Faster: +0.25x
The next time you’re watching an HTML5 video—the majority of web videos use this format now—just right click to control video speed. I tested this on a wide variety of websites and didn’t run into any issues.
In a growing list of selected websites, Speedifier will give you a dedicated button on the video. So far, Speedifier adds a button to these websites:
- Wall Street Journal
- Prime Video
If a video needs an external plugin like Silverlight or Flash, Speedifier doesn’t support it. You can request that a Speedifier be added to a website you want by emailing Arno at firstname.lastname@example.org.