Google continues it's push for mobile first world with the expansion Google is aggressively expanding their transcode process starting in Indonesia in April, India in June and it seems now starting to show up globally according to Ben Pfeiffer. Cheers to Saijo George for pointing out it's progress since April 2015 around the world. Google is pushing this for faster and lighter mobile pages for people searching Google on slow mobile connections. Below you can see the comparison loading blogspot without on the left side and with on the right side which shows a fairly substantial improvement.Their experiments claim their optimised pages load 4x faster and use 80% less bandwidth which sounds great but what does it sacrifice?How to test transcoded view?If you have a search console account you can test how your website looks using their transcoder which will create a QR code you can scan with your mobile or use the Chrome device mode as shown in the screenshot below. Can I Opt-Out of Transcoding?Yes, if you do not want Google to transcode your pages you can add the following meta tag to HTTP header to your page and if Googlebot sees this page your page will not be transcoded.<meta http-equiv="Cache-Control" "no-transform" />Downsides of Opt-Out of Transcoding?If you do choose to opt-out Google will label your website results to indicate to yours that your pages may take longer and may use more data. This will likely impact your CTR from mobile devices and could potentially include desktop devices on slow connections. You can view more FAQ on their page.Ads and Revenue Impacts of Transcoding?As of May 2015 Google only supports a handful of Ad Networks including obviously AdSense but also Sovrn and Zedo but strangely still not supporting DoubleClick for Publishers (DFP). They do state that they will support more ad networks but no timeline on this yet. Transcoding also limits the number of ads showing on a single page and that limit is hardcoded to 3 currently. Google selects ads requested in order by the original page, so if your high CPC or CPM banners are loaded last Google will load them last or drop them if you are showing more than 3 ads.Google also advises that they only support two ad formats for transcoding 320x50 and 300x250 if you want your ad network to be included on transcoded pages.Why Shouldn't I Transcode my pages?A big reasons to not transcode your pages is that some Proxy and CDN services encode your media. This is not likely an issue if you don't use many features like images or music but could have implications if you do. It can have a huge impact if you opt-out for most large websites that use CDN for images and media files. If you are unsure if you are using CDNs you can use CDN Finder.If you need more details on Proxoy Decision to Transform W3C Working group has some notes on the topic, but be careful if you opt-out you might find some elements might break and your CTR from mobile devices might drop.