pronunciation - ブラウザ or ブラウザー? Words borrowed from English which end with -er

I noticed that some (most? all?) words that were borrowed from English and end with -er in English can have either short or long vowel at the end:

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  browser - can be ブラウザ or ブラウザー

  
  



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  driver - can be ドライバ or ドライバー

  
  


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  computer - can be コンピュータ or コンピューター

  
  

Is one option preferred over another? There doesn't seem to be much consistency so is just a matter of personal choice? Dictionaries usually list both options so that doesn't offer much help.

Answer

Japanese 国語審議会 (National Language Council) recommends longer (with ー) forms since 1991. So foreign words in textbooks for elementary school students usually have trailing "ー".

http://www.mext.go.jp/b_menu/hakusho/nc/k19910628002/k19910628002.html

注3　英語の語末の‐er,　‐or,　‐arなどに当たるものは，原則としてア列の長音とし長音符号「ー」を用いて書き表す。ただし，慣用に応じて「ー」を省くことができる。 〔例〕　エレベーター　ギター　コンピューター　マフラー

Japanese version of Microsoft Windows switched from "マイ コンピュータ" to "マイ コンピューター" as of Windows 7, according to this recommendation.

「コンピュータ」→「コンピューター」に　MSが表記ルール変更 http://www.itmedia.co.jp/news/articles/0807/25/news090.html

However, as the article above explains, another standard from Japanese Industrial Standards (JIS規格の表記ガイドライン JIS Z 8301) has long said that "ー" should be omitted if the word is long enough, while convention always takes precedence.

http://kikakurui.com/z8/Z8301-2011-01.html

a)その言葉が 3 音以上の場合には，語尾に長音符号を付けない。

b)その言葉が 2 音以下の場合には，語尾に長音符号を付ける。

So your choice depends on the situation. Technologists and scientists tend to prefer shorter versions, while news media for general populations usually prefer longer ones.

(Here's NHK's policy: https://www.nhk.or.jp/bunken/summary/kotoba/gimon/159.html)

But anyway, in general, most Japanese don't care at all in their daily lives.