The rules of Internet etiquette are not universal, but using all capitals in online communications is discouraged for both technical and social reasons. Some online forms may ask specifically for responses in all caps, often to keep responses consistent, but this is relatively uncommon. When addresses or form responses are written in capital letters, it can be difficult for the recipient to read and give the reader a negative perception of the writer. Certain online forms may also be case-sensitive, which means any capitals typed during the creation of a password or email address must remain that way later.
One of the main reasons why the use of all capitals is discouraged is social in nature. It is difficult to convey emotions, irony, or sarcasm in most electronic communications, so many emailers and chatroom participants use capital letters to express anger or other strong emotions. THE EFFECT IS THE APPEARANCE OF SHOUTING, which may not be the sentiment you wish to convey. Other typographical effects, such as emoticons, can convey more subtle emotions, but the use of uppercase writing is perceived as far from subtle.
Another reason many online form users dislike all capitals is general readability. Early computer programs had difficulty recognizing lower case letters, so the use of all capital letters was the norm. As more advanced word processing programs became available, fewer computer users felt the need to use all capitals in their electronic communications. Some online forms still request responses this way, but often only when the responses are relatively short and the recipients seek a level playing field without improper lower or upper case typos affecting their decisions.
When a form does not require the use of all capital letters and you answer this way anyway, it can make your responses stand out from those of other people — but often not in a good way. People who are new to online communications or who are not comfortable with the Internet may use capital letters more than they should, so filling out a form this way or even using all caps in your email address can make it look like you are inexperienced.
Lengthy passages written in all capitals can very difficult to read. EVEN A SIMPLE EXPLANATION OF WHY USING ALL CAPITAL LETTERS IS NOT ADVISABLE CAN QUICKLY TURN INTO A BLUR OF LETTERS OVER TIME. Capitals do have their place in electronic communications, especially as headers and titles, but most readers prefer to see electronic text as a form of typewritten material, with familiar upper and lower case fonts. The use of all capital letters can negatively affect a reader's reading speed or an editor's proofreading ability.
Writing in all capitals should only be used to express very strong emotion or in response to short online form queries. Be sure to check the website's rules concerning the use of letter case before submitting your information electronically.