Browser game running slowly? Nine fixes that actually work

First, work out what kind of slow it is

Three different problems get called lag. A game that takes a long time to appear and then runs fine is a download problem: the whole game, often tens of megabytes, is fetched on first load and cached afterwards, so the second visit is faster. A game that runs at a steady but low frame rate is a graphics problem. A game that runs smoothly and then freezes for half a second every few seconds is usually another program or tab competing for the machine.

The fixes below are grouped by which of those you are seeing. If the game is a 3D title exported from Unity or a similar engine, expect it to be the heaviest thing open in your browser; the 2D puzzle and card games on this site are far lighter and rarely need any of this.

The nine fixes

In rough order of how often each one is the answer:

1. Close other tabs, especially video. A streaming video or a busy web app in another tab takes the same graphics and CPU budget the game needs. Close them rather than leaving them in the background.
2. Make sure hardware acceleration is on. In Chrome and Edge it is under Settings → System → "Use graphics acceleration when available"; in Firefox under Settings → General → Performance (untick "Use recommended performance settings" to see it). If it was off, turn it on and restart the browser. This single setting is the difference between the graphics card drawing the game and the CPU doing it badly.
3. Check what the browser thinks of your graphics. In Chrome or Edge, open a new tab and type chrome://gpu (edge://gpu in Edge). Near the top, "WebGL" and "WebGL2" should say "Hardware accelerated". If they say "Software only" or "Disabled", the fix above has not taken effect or your graphics driver is blocked, and the next step applies.
4. Update the graphics driver. Browsers keep a list of drivers with known bugs and switch to slow software rendering when they see one. On Windows, update through the manufacturer's tool (Intel, NVIDIA or AMD) rather than Windows Update, which is often years behind. On a Mac and on Chromebooks, the driver ships with the operating system, so run the normal system update.
5. Disable extensions for the game page. Ad blockers, privacy tools and page-modifying extensions inject scripts into every frame, including the game's. Try the game in a private window with extensions disabled; if it is smooth there, allow-list the site in the offending extension rather than switching the extension off entirely.
6. Plug in and turn off battery saver. Laptops and phones throttle the processor and graphics chip on battery, and browser battery-saver modes cap frame rates. A game that stutters unplugged and runs cleanly on mains power is not broken.
7. Use fullscreen. The fullscreen button on the player reduces how much of the page the browser has to draw around the game and, on some systems, lets the game run at a lower internal resolution that suits your screen better.
8. On a phone, close background apps and let it cool. Phones throttle hard when warm. A game that was fine for five minutes and then turned to treacle is a thermal problem; give the phone a minute and avoid playing while it charges.
9. Accept that some games are too heavy for the device. An eight-year-old laptop with integrated graphics will not run a large 3D driving game well no matter what you change. The reviews on this site say which games are heavy; the Chromebook guide covers what to expect on low-end hardware.

Why ad blockers in particular cause trouble

Browser games from a distributor load their adverts, their analytics and often their save system from a handful of domains. An aggressive blocker that stops one of those requests can leave the game waiting on a script that never arrives, which shows up as a long pause before the game appears, a black frame, or a game that starts and then hangs at the first level change. Blocking is your choice, but if a game misbehaves only when the blocker is active, that is the cause. The guide on what an iframe can and cannot do explains what those scripts have access to.

Mobile browsers behave differently

On a phone you have fewer settings to change and more that is decided for you. Safari on iPhone and Chrome on Android both accelerate WebGL by default, so the driver and acceleration steps do not apply. What does apply: low-power mode throttles noticeably, a hot phone throttles more, and a page that has been open for a long time in a background tab may be reloaded from scratch when you return, losing any game state that had not been saved yet.

Portrait games, which most mobile-first puzzle titles are, are lighter than landscape 3D ones. If a landscape game is unplayable on your phone, the same game is usually fine on the laptop it was designed for; the review's controls section says which input the developer built around.

When the game is the problem

Occasionally none of this helps because the game itself has a bug or an update broke it. Signs: it is slow for everyone on every device, or it worked last week and not this week with no change on your side. Reviews on this site are revised when a game changes materially; if you hit this, the contact page is the fastest way to tell us, and we will re-test.