After reading usage of the phrase "UTF-8 encoded" ("UTF-8-encoded) at, for example, stackoverflow.com, in Howto identify UTF-8 encoded strings, and in an excerpt

...every character can be UTF-8 encoded.

from this answer, I began to question whether writing "UTF-8-encoded" is an overuse of hyphens, but a quick read over

Confusion over the general rules governing the use of the hyphen in English

When should compound words be written as one word, with hyphens, or with spaces?

indicates to me that "UTF-8-encoded" is correct usage of hyphens.

Is "UTF-8 encoded", though, correct and not require an additional hyphen? If it it is correct, why isn't the hyphen necessary?

  • 2
    It ought to have both hyphens, though I imagine that encoded with UTF-8 might be less unseemly.
    – Anonym
    May 25, 2015 at 4:10

3 Answers 3


I think it's something of a matter of personal style, or if writing for publication, the style guide of the intended publication. The name of the coding method is "UTF-8" (cf. http://en.wikipedia.org/wiki/UTF-8), so the hyphen between the character "F" and the character "8" is a part of the name. But looking at the first link you provide, the hyphen is not required from case 1 because the two parts, "UTF-8" and "encoded" do not have a combined meaning that differs to any significant degree from the phrase "encoded with UTF-8". It's also not required from case 2, because as pronounced, "8" ends in a consonant, and "encoded" begins with a vowel.

On the other hand, according to your link to question 889, one could argue that there should be a hyphen, but according to that site, only in the exceptional case that the phrase precedes the noun it modifies, as in "UTF-8-encoded document". But it's not clear to me that this exception applies in the absence of the following noun, for example in the construct "The document is UTF-8 encoded." And since this last statement is functionally equivalent to "The document is encoded in UTF-8.", I don't think that the hyphen is necessary. But I don't think a hard and fast rule applies here, and I can conceive of cases where I might see the construct with a hyphen between the "f" and the "8", and between the "8" and the following word might be useful.

  • If we replace "UTF-8" here with non-hyphenated manners to encode, like "binary", "Unicode" or "MD5", to precede "encoded document", would the general usage of the hyphen probably have it connect the encoding type (e.g. binary) to the word encoded, e.g. "binary-encoded document"?
    – T. Webster
    May 25, 2015 at 5:49
  • Unicode, of course, is UTF-8, so I would generally not insert a hyphen between "unicode" and "encoded", and so in extending the principle would not insert a hyphen in "binary encoded" or "MD5 encoded", either. But this is colored by my own personal view that "binary encoded" and the others are not very euphonious, and are too admitting of ambiguity for my taste, and I tend to avoid them on the basis of my personal stylistic preferences.
    – brasshat
    May 25, 2015 at 5:53
  • @brasshat Unicode and UTF-8 are not equivalent terms. UTF-8 is an Unicode Transformation Format. Saying "unicode encoded" is context sensitive and would either refer to representing text with codepoints, or the encoding of such codepoints with an unspecified transformation format. May 25, 2015 at 12:13

It depends on usage. As a predicate modifier, it does not need the second hyphen, just as

  • This app is up to date.
  • This app is [the] state of the art.

do not need hyphens.

As a preposed subject modifier, it does.

  • Up-to-date apps are the best.
  • No, state-of-the-art apps are even better!


  • UTF-8-encoded strings should be used.


  • These strings should be UTF-8 encoded.

However, as commenters mentioned, the hyphen problem can often be finessed:

  • These strings {are/should be} encoded as UTF-8.


I believe this is a technical token or symbol used in the context of computer programming, where such tokens cannot contain whitespace (or is more error-prone if they do).

In the context of English, you should not use the second hyphon, as in:

I sent you a UTF-8 encoded document.

Using UTF-8-encoded in this context looks horrible.

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