Facebook regularly tweaks every part of its experience to encourage more users to stick around, but the social media network’s latest update could have some websites and publishers worried. Facebook will now start elevating and downgrading sites on its News Feed depending on how fast their pages load.

As part of the new update, sites that load slowly or poorly will appear less often on a user’s News Feed. The company expects the update to roll out gradually over the next few months and acknowledged that the move could hurt referral traffic for poorly performing sites.

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In a post Wednesday, Facebook detailed its reason for the move:

With this update, we’ll soon take into account the estimated load time of a webpage that someone clicks to from any link in News Feed on the mobile app. Factors such as the person’s current network connection and the general speed of the corresponding webpage will be considered. If signals indicate the webpage will load quickly, the link to that webpage might appear higher in your feed.

For years, we have taken many factors into account to make sure people quickly see relevant stories to them — including the type of device you’re on or the speed of your mobile network or wifi connection. For example, if you are on a slower internet connection that won’t load videos, News Feed will show you fewer videos and more status updates and links. And to help load stories faster for people on slow or poor network connections, we prefetch stories by downloading mobile content before someone clicks a link, which we’ve seen can shorten load time for webpages by more than 25%.

For users, there’s virtually no downsides for the updates. Poor website performance that bogs down your browser is an obvious problem when you’re online and penalizing sites that run slowly is an easy way to encourage users to use Facebook for longer. According to Facebook, 40 percent of users leave a website if it takes three seconds or longer to load. Facebook also isn’t the only company to use site loading speed as a metric, as Google has been doing the same for its search results since 2010.

However, Facebook also has a notable second reason for the move and it goes beyond just making the News Feed faster for users.

Facebook’s Instant Articles platform, which launched in early 2015, is a way for publishers to natively produce and upload articles just for Facebook users. In particular, Instant Articles also allows pages to load faster thanks to a stripped down mobile-friendly layout that’s built exclusively for Facebook. Many publishers have jumped on board with the service, though some have stayed away due to concerns about advertising revenue and potentially making Facebook a primary carrier for their content.

Behind the scenes, Facebook has worked to make Instant Articles more open to publishers. In the past few months, the company has tweaked various advertising publisher features on Instant Articles and also plans to allow paid subscription paywalls later this year.

While Instant Articles wasn’t mentioned in Facebook’s initial announcement, it still indirectly benefits from the company’s News Feed tweak. Publishers could previously get by with outdated site design, but if they don’t want to put in the work to update their backend to avoid losing Facebook traffic, migrating content to Instant Articles would likely be an easier workaround.

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To help out publishers, Facebook also released a guide with tips to improve website browsing and navigation performance.

Facebook’s 10 Speed Best Practices

  1. Minimize landing page redirects, plugins, and link shorteners

  2. Compress files to decrease mobile rendering time

  3. Improve server response time by utilizing multi region hosting

  4. Remove render-blocking javascript

  5. Use a high-quality content delivery network to reach your audience quickly

  6. Remove redundant data that does not impact how the page is processed by the browser

  7. Optimize images to reduce file size without diminishing visual quality

  8. Reduce the size of above the fold content to prioritize visual content

  9. Use asynchronous scripts to streamline page render time

  10. Dynamically adjust the content for slower connections/devices