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I mean 'view source' not generated source. What I tried to say is that Google will see exactly the same code as you do when you right click on a page and click 'View source code'. So to answer your first question _' I have a H1 that will be replaced with a canvas by jquery script. Will search engines see the H1 or the canvas?'  _Just check the source code of your page to find out. Javascript/ajax can cause problems for Google to index the content as far I know, but I'm not an expert in this.

Thanks guys! So my interpretation of your feedback and the short answer to my questions are: 1. Yes, it's worth doing. 2. Yes, it's worth doing. Cheers!