Why using ALL CAPS in a subject line is a bad idea

I’ve just finished reading Debbie Weil’s The Corporate Blogging Book. It’s fantastic! She really got my creative juices flowing and gave me loads of ideas about blogging … I’ll post my thoughts and highlights from the book soon.

Right now I want to mention this most interesting little nugget of a stat that I gleaned from the book’s resource section: Jakob Nielsen‘s Weblog Usability: The Top Ten Design Mistakes. It’s an extremely useful article – as usual with Jakob. But it was this particular bit that jumped out at me.

“In browsing weblog headline listings to extract these examples, I noticed several headlines in ALL CAPS. That’s always bad. Reading speed is reduced by 10% and users are put off by the appearance of shouting. ”

There’s something deeply annoying about all caps – it feels like shouting and feels very spammy. But I didn’t have a factoid to back up these ‘feelings’ … and here it is – they reduce reading speed by 10%. All Caps act as a big STOP SIGN to the brain. They create a speed bump. Going heavy on the caps means your readers may stop reading altogether.

Jakob is referring to blog titles, but really this is 110% applicable to subject lines in emails – and RSS/Web feeds for that matter. The VERY sparing use of them for emphasis can work – but tread carefully.