I'm curious to know more about what triggers the Reader option in Safari and what does not. I wouldn't plan to implement anything that would disable it, but curious as a technical exercise.

Here is what I've learned so far with some basic playing around:

• You need at least one H tag
• It does not go by character count alone but by the number of P tags and length
• Probably looks for sentence breaks '.' and other criteria

Safari will provide the 'Reader' if, with a H tag, and the following:

• 1 P tag, 2417 chars
• 4 P tags, 1527 chars
• 5 P tags, 1150 chars
• 6 P tags, 862 chars

If you subtract 1 character from any of the above, the 'Reader' option is not available.

I should note that the character count of the H tag plays a part but sadly did not realize this when I determined the results above. Assume 20+ characters for H tag and fixed throughout the results above.

Some other interesting things:

• Setting <p style="display:none;"> for P tags removes them from the count
• Setting display to none, and then showing them 230ms later with Javascript avoided the Reader option too

I'd be interested if anyone can determine this in full.