I’m wondering if anyone knows if it’s possible to enable sub-pixel rendering in an HTML5 canvas in Chrome (and/or Safari).
Chrome does sub-pixel rendering in HTML, and FF does it for both HTML & Canvas rendering. Specific issue pictured below:

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Short answer: No. Not possible
This is one of two topics that frustrates a lot of Canvas users.
Subpixel rendering/anti-aliasing of any kind is up to the browser. This means that different browsers are prone to render things in different ways.
A lot of people have asked for anti-aliasing to be an option that can be turned on or off for a specific context. No luck of anything like that yet.
Chrome in particular you’ll need to keep an eye on, because the way they have handled sub-pixel rendering has changed drastically over the past 4 months. If you start using the Chrome developer channel you’ll get a preview of the things they keep trying out. They’ve been doing quite a bit of testing in this area, and have even pushed some drastic regressive changes that I’ve complained about.
The takeaway here is that: