We already know that enabling Flash in the browser can impact your computer's performance and, along with other factors, slow browsing to a crawl. PCWorld did some tests to find out just how much of a difference running Flash makes.
In a word: significant. With both Microsoft Edge and Opera, having Flash enabled consumed over 80% of the test computer's CPU cycles, compared to 33% and 7%, respectively, without Flash. Flash also consumed a significant amount of memory with both browsers.
Firefox's benchmarks weren't so dramatic, but the experience was the same:
Firefox? Well, Firefox did swimmingly as well, when you removed Flash from the equation. It consumed 1.65 GB, and needed only 24.5 per cent of the CPU. But after I downloaded Flash, Firefox seemed to throttle itself. The browser never climbed above 29.1 per cent of the CPU, but some tabs were unresponsive minutes after loading, and I had to manually check each tab to check on its progress. That was totally unacceptable.
There are no comparison numbers for Chrome in this article, which notes that with Flash enabled Chrome consumed 4.23 GB of memory and 71.4% of the CPU, so better than Microsoft Edge. PCWorld senior editor Mark Hachman tells me, however, that there is a difference for Chrome with Flash disabled, but those numbers will be revealed in an upcoming browser roundup they're doing. In the meantime, you can test for yourself by going to chrome://plugins and disabling Flash.
To do this test, PCWorld used a Lenovo Yoga 12 notebook with an Intel Core i7 processor, Windows 10 Pro (64-bit), and 8 GB of memory. They loaded 30 sites in separate tabs, then recorded the CPU load and memory consumption -- for the latest versions of the browsers with and without Flash installed or enabled.
YMMV. Some sites aren't functional without Flash, your computer might have better or worse specs than this test system, and you might not be a 30-tabs at a time kind of browser user. But if you need any more reasons to uninstall or disable Flash (besides privacy issues and frequent security vulnerabilities), this might be another big one.
As an alternative, you can use your browser's click-to-run option for Flash to only enable it when necessary.