Flash is a problem and it has been one for a long time. It slows down web-page loading, it drains batteries and most importantly, it has a long history of security vulnerabilities. Google has been taking steps to protect users from Flash since at least 2011 when they released a tool that converted Flash to HTML5. In December 2016, HTML5 became the default for Chrome, Google’s world-leading desktop browser. How Chrome handles the small minority of websites that still use Flash has led to confusion about whether Flash content can be accessed in Google’s browser.
Flash is a multimedia platform that delivers text along with raster and vector graphics. It can stream audio and video and can capture input from keyboards, mice, mics and cameras. It has largely been supplanted by HTML5 which can do these things faster, more efficiently, and much more safely.
In August 2016, Google announced that HTML5 would be the default for the Chrome browser beginning with Chrome 55 which was released in early December. However, when Chrome 55 released, the HTML5 default was only enabled for 1% of users. This led to some confusion as many blogs and websites that relied only on the August announcement reported that HTML5 was the default when Chrome 55 released while others that bothered to check whether Flash was being blocked reported that Flash content was still being rendered in Chrome 55. HTML5 became the default in Chrome for all users with the release of Stable Chrome 56 this month. (The current 64-bit version of Chrome is 56.0.2924.87.)
More confusion is likely to arise over the coming months because of the way Google is handling web content that is only available in Flash. Sometimes a pop-up window will ask the user if they want to enable Flash when Flash-only content resides on a website. If the user enables Flash, Chrome will allow Flash whenever the user returns to the site.
The key word here is “sometimes.” Sometimes the window pops up and sometimes it doesn't. Whether or not the window appears will change depending on what month it is and how the user has interacted with the website in the past.
Here’s what’s going on: Google measures user interaction with a metric they call the Site Engagement Index (SEI). The SEI ranges from 0 to 100 and is based on direct navigation to the website along with time spent and media playback on the site. If a user does not visit a site for a while, the SEI score decays toward zero. You can check your SEI by entering "chrome://site-engagement/" in your browser bar.
Whether or not a window pops up asking if the user wants to enable Flash on a particular website depends on the user’s SEI for that site. If the SEI is below a threshold, the window pops up. The current threshold is set at two. This means that users will only see the pop-up window on sites they rarely visit. If you go to a site you visit regularly, you will not get the pop-up and the Flash content will be blocked leaving you to try to figure out some way to get Flash to work if you really want to see the blocked content.
The SEI threshold is scheduled to increase throughout the rest of the year until it reaches the maximum score of 100 in October. Here’s the schedule of threshold changes.
| Month | SEI Threshold |
| February | 2 |
| March | 4 |
| April | 8 |
| May | 16 |
| June | 32 |
| July | 32 |
| August | 32 |
| September | 64 |
| October | 100 |
In October, every website that contains Flash-only content will prompt users with a pop-up window.
Why is Google doing this? If the SEI threshold was set at 100 today, users that regularly visit a lot of sites with Flash-only content would be subjected to a lot of pop-up windows. This could become a real annoyance which is something Google would like to avoid. They would also like to avoid motivating annoyed users to switch browsers or change the default in Chrome to allow Flash content all the time.
Very few websites still use Flash because it has serious problems and a much better alternative exists in HTML5. W3Techs estimates that only 7.1% of all websites use Flash. If you visit these websites and Chrome is your browser, you may notice oddities and apparent inconsistencies in how the websites behave in Chrome. These problems are scheduled to go away in October when Chrome will pop-up a window asking if you want Flash enabled for any website you visit with Flash-only content.
