Starting on February 11th, Twitter is changing the way it handles PNG images that are uploaded to its platform. Here is everything you should know about this change.
Twitter has always supported JPEG and PNG formats for uploaded images, and over the years it has made improvements to help drive faster load times which at the same time improving image quality. Now, starting on February 11th, Twitter is focusing on PNG images and how it will continue to handle the format from now on.
So, what changes are being made? For one, Twitter will now be providing consistent behavior when it comes to uploading PNGs. In the past, the way Twitter handled PNG uploads “could lead to large PNG images being used when a JPEG would have been preferable for image load latency and user data costs,” explains Nolan O’Brien in a recent post. The changes will address this. Furthermore the changes will be applied to all images uploaded to the platform.
JPEGs uploaded to Twitter will remain in JPEG format transcoded to 85% JFIF quality if the image that is being uploaded has a higher quality – so no change there. However WebP images that are uploaded will be converted to JPEG at 85% JFIF quality. Previously, when WebP images were uploaded, some would occasionally be converted to PNG. This will cease. While WebP will remain a supported upload format, Twitter “will continue to not serve images as WebP.”
On the other hand, PNG images uploaded to Twitter will now follow a specific process depending on type of PNG they are. Overall, the change will lead to more PNG images to be converted to JPEG, while certain PNG images will remain as PNG “as long as they meet criteria that has been set to achieve the image load performance needed at a global scale.”
As explained further by O’Brien, “lower color depth PNG images are encoded small enough to have better sizes than a JPEG counterpart, and we want to keep these PNG images. For high color depth PNG images, they are most often very large compared to a JPEG and delivering those images efficiently at a global scale is not feasible.”
Twitter might consider to keep them as PNG, but in most cases they will be converted to JPEG instead. The following chart shows a breakdown the different types of PNG and Twitter’s action when they are uploaded:
So, essentially, the most common PNGs – PNG-24 and PNG-32. will be tested to determine if they will remain PNG, or if they will be converted to JPEG. When tested, Twitter will look at an image’s file size and compare it with the size of a converted JPEG file size. If the PNG is small enough compared to the converted JPEG, Twitter will let it through. However, due to significant difference in size between the two file types, conversion to JPEG is more likely for these PNGs. On the other hand PNG-8 – a lesser used version of the format – will always stay as PNG and will not be converted.
This news will be of particular interest to creators who upload images to Twitter, and want to be sure that compression doesn’t occur. While this can’t be guaranteed, they at least have the chance to export images that are already close to optimised for Twitter. PNG images with solid colour and exported as PNG-8 will be a particularly good way to upload lossless quality images to Twitter. These will obviously be left untouched, and so will not be affected by artifacting as much as JPEGs are. PNG-8 files also support alpha, so transparency is an option here, while it is not when using JPEGs.
As you will already know, images with transparency that are converted to JPEG have a white layer added instead.