Deciding on the right video dimensions to use for the web can be difficult. Unfortunately, there is not a one fits all size because it depends largely on your target audience. Usually, your best bet is to offer multiple sizes to ensure your video works for most of your website’s visitors. Now that devices like the iPhone and iPod are gaining in popularity, you may want to also offer a compatible size for these devices as well. To make things even more complicated, your video sizes should be evenly divisible by 16 to ensure the best possible output.
The following frame sizes should work well for the large majority of websites whose visitors are on broadband connections. If you need to target users on slower connections or other devices, you will need to create additional versions. Since most videos are either 16:9 (HD) or 4:3 (SD), I will provide dimensions based on both. Keep in mind that video does not scale up well to larger sizes, so if you source video is smaller than any of these sizes, you should only use the ones at the same sizes or smaller.
1280×720 – iPad compatible*
512 x 288 – iPhone/iPod Touch compatible*
256×144 – If you do not need to support users with connections lower than 1mbps, you can omit this option.
1024×768 – iPad compatible*
640×480 - iPhone/iPod Touch compatible*
320×240 - If you do not need to support users with connections lower than 1mbps, you can omit this option.
Note about SD video: If your source video is NTSC/DV, you should scale non-uniformly to 640×480/320×240 since the pixel aspect ratio of NTSC/DV is not designed for computer monitors.
* iPad/iPhone/iPod Touch compatible resolutions also require special encoding settings and a compatible video player to work correctly.
If you have any questions about these dimensions or need recommendations for your unique circumstances, please be sure to post in the comments!