All-caps text—mean­ing text with all the let­ters cap­i­tal­ized—is best used sparingly.

At stan­dard body text sizes, cap­i­tal let­ters—or sim­ply caps—are harder to read than nor­mal low­er­case text. Why? We read more low­er­case text, so as a mat­ter of habit, low­er­case is more fa­mil­iar and thus more leg­i­ble. Fur­ther­more, cog­ni­tive re­search has sug­gested that the shapes of low­er­case let­ters—some tall (d h k l), some short (a e n s), some de­scend­ing (g y p q)—cre­ate a var­ied vi­sual con­tour that helps our brain rec­og­nize words. Cap­i­tal­iza­tion ho­mog­e­nizes these shapes, leav­ing a rec­tan­gu­lar contour.

That doesn’t mean you shouldn’t use caps. But use them ju­di­ciously. Caps are suit­able for head­ings shorter than one line (e.g., “Table of Con­tents”), head­ers, foot­ers, cap­tions, or other la­bels. Caps work at small point sizes. Caps work well on let­ter­head and busi­ness cards. Al­ways add let­terspac­ing to caps to make them eas­ier to read, and make sure kern­ing is turned on.

DON’T CAP­I­TAL­IZE WHOLE PARA­GRAPHS. THIS HABIT ORIG­I­NATED WITH LAWYERS AND HAS IN­FECTED SO­CI­ETY AT LARGE. MANY WRIT­ERS SEEM TO THINK THAT CAP­I­TAL­IZA­TION COM­MU­NI­CATES AU­THOR­ITY AND IM­POR­TANCE. “HEY, LOOK HERE, I’VE GOT SOME­THING IM­POR­TANT TO SAY! I DE­MAND THAT YOU PAY AT­TEN­TION TO THIS!” BUT A PARA­GRAPH SET IN ALL CAPS IS VERY HARD TO READ. IT’S EVEN WORSE IN BOLD. AS THE PARA­GRAPH WEARS ON, READ­ERS FA­TIGUE. IN­TER­EST WANES. HOW ABOUT YOU? DO YOU EN­JOY READ­ING THIS? I DOUBT IT. BUT I REG­U­LARLY SEE CAP­I­TAL­IZED PARA­GRAPHS THAT ARE MUCH LONGER THAN THIS. DO YOUR READ­ERS A FA­VOR. STOP CAP­I­TAL­IZ­ING WHOLE PARAGRAPHS.

All-caps para­graphs are an ex­am­ple of self-de­feat­ing ty­pog­ra­phy. If you need read­ers to pay at­ten­tion to an im­por­tant part of your doc­u­ment, the last thing you want is for them to skim over it. But that’s what in­evitably hap­pens with all-caps para­graphs be­cause they’re so hard to read.

To em­pha­size a para­graph, you have bet­ter op­tions. Use rules and bor­ders. Add a head­ing that la­bels it Im­por­tant. Run it in a larger point size. But don’t cap­i­tal­ize it.

There are two ways to put caps in a doc­u­ment. The pop­u­lar method is to en­gage the caps-lock key at the left edge of the key­board and type away. That works, but it makes cap­i­tal­iza­tion a per­ma­nent fea­ture of your text.

The pre­ferred method is to ap­ply all-caps for­mat­ting to nor­mally typed text. That way, you can tog­gle cap­i­tal­iza­tion on and off with­out re­typ­ing the text itself.