This is a bit difficult to answer, as it depends on many factors.
In general, you can assume that you will get performance close to native apps for the GPU side, as the WebGL graphics API uses your GPU for hardware accelerated rendering - there is just a little overhead for translating WebGL API calls and shaders to your OS graphics API (typically DirectX on Windows or OpenGL on Mac or Linux).
For the CPU side, all your code is translated into asm.js JavaScript. So what kind of performance you can expect depends a lot on the JavaScript engine of the web browser used, and there are some pretty significant differences there currently. At the point of this writing (November 2015), Microsoft Edge and Mozilla Firefox deliver the best performance on Unity code, as these are currently the only browsers which make use of the asm.js spec to use an optimized AOT compilation path of JavaScript code for that case, which delivers performance within a factor of less then 2x slowdown compared to native code for many programming benchmarks - and that factor also matches results we’ve seen from different unity content we deployed to WebGL and ran in Firefox and Edge.
There are some other considerations, though. Currently, the JavaScript language does neither support multi-threading, nor SIMD. So, any code which benefits from these features will see bigger slowdowns then other code. You cannot write threading or SIMD code in WebGL in your scripts, but some engine parts are normally multi-threaded or SIMD optimized, and will run less performant on WebGL because of this. An example is the skinning code, which is both multi-threaded and SIMD-optimized. You can use the new timeline profiler in Unity to see how Unity distributes work to different threads on non-WebGL platforms. Longer term, we are hoping that these features will become available on WebGL as well.
For best performance, set the optimization level to “Fastest” in the Build Player dialog, and set “Exception support” to “None” in the player settings for WebGL.
The Unity profiler is supported in WebGL, see here how to set it up.
If the Run in background is enabled in the WebGL Player Settings, or if you enable Application.runInBackground, then your content will continue to run when the canvas or the browser window loses focus.
However, it should be noted that browsers may throttle content running in background tabs. If the tab with your content is not visible, your content will only be updated once a second in most browsers. Note that this will cause Time.time to progress slower than usual with the default settings, as the default value of Time.maximumDeltaTime is lower than one second.
You may want to run your WebGL content at a lower frame rate in some situations to reduce CPU usage. Like on other platforms, you can use the Application.targetFrameRate API to do so.
When you don’t want to throttle performance, set this API to the default value of –1, rather then to a high value. This allows the browser to adjust the frame rate for the smoothest animation in the browser’s render loop, and may produce better results than Unity trying to do its own main loop timing to match a target frame rate.
Did you find this page useful? Please give it a rating:
Thanks for rating this page!
What kind of problem would you like to report?
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.
Thanks for letting us know! This page has been marked for review based on your feedback.
If you have time, you can provide more information to help us fix the problem faster.
Provide more information
You've told us this page needs code samples. If you'd like to help us further, you could provide a code sample, or tell us about what kind of code sample you'd like to see:
You've told us there are code samples on this page which don't work. If you know how to fix it, or have something better we could use instead, please let us know:
You've told us there is information missing from this page. Please tell us more about what's missing:
You've told us there is incorrect information on this page. If you know what we should change to make it correct, please tell us:
You've told us this page has unclear or confusing information. Please tell us more about what you found unclear or confusing, or let us know how we could make it clearer:
You've told us there is a spelling or grammar error on this page. Please tell us what's wrong:
You've told us this page has a problem. Please tell us more about what's wrong:
Thanks for helping to make the Unity documentation better!
When you visit any website, it may store or retrieve information on your browser, mostly in the form of cookies. This information might be about you, your preferences or your device and is mostly used to make the site work as you expect it to. The information does not usually directly identify you, but it can give you a more personalized web experience. Because we respect your right to privacy, you can choose not to allow some types of cookies. Click on the different category headings to find out more and change our default settings. However, blocking some types of cookies may impact your experience of the site and the services we are able to offer.
More information
These cookies enable the website to provide enhanced functionality and personalisation. They may be set by us or by third party providers whose services we have added to our pages. If you do not allow these cookies then some or all of these services may not function properly.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
These cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising. Some 3rd party video providers do not allow video views without targeting cookies. If you are experiencing difficulty viewing a video, you will need to set your cookie preferences for targeting to yes if you wish to view videos from these providers. Unity does not control this.
These cookies are necessary for the website to function and cannot be switched off in our systems. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. These cookies do not store any personally identifiable information.