Why shouldn't `'` be used to escape single quotes?

Question

As stated in, When did single quotes in HTML become so popular? and Jquery embedded quote in attribute, the Wikipedia entry on HTML says the following:

The single-quote character ('), when used to quote an attribute value, must also be escaped as ' or ' (should NOT be escaped as ' except in XHTML documents) when it appears within the attribute value itself.

Why shouldn't ' be used? Also, is " safe to be used instead of "?

[`'` is valid in HTML5](http://stackoverflow.com/a/18551371). — Zaz, Aug 31 '13 at 18:24
There's a "not" missing from the Wikipedia quote, which should be "… when ***not*** used to quote an attribute value …". — Jake, Aug 22 '21 at 00:40
Oh, so if you don't care about anything older than IE11, `'` is fine. — General Grievance, Sep 01 '21 at 13:43
@Calculuswhiz But of course it was a valid concern back in 2010, when this question was asked... — Mr Lister, Nov 19 '21 at 14:12

score 215 · Accepted Answer · edited Oct 04 '13 at 01:46

215

" is on the official list of valid HTML 4 entities, but ' is not.

From C.16. The Named Character Reference ':

The named character reference ' (the apostrophe, U+0027) was introduced in XML 1.0 but does not appear in HTML. Authors should therefore use ' instead of ' to work as expected in HTML 4 user agents.

edited Oct 04 '13 at 01:46

Fyodor Soikin

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answered Jan 18 '10 at 03:37

cletus

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`"` is on the list though, so should be OK. – Bennett McElwee Jan 18 '10 at 03:56
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Today happened that on an IE8 machine ' was not parsed, so the user sees the code. Replacing with ' solved the problem. – Michele Gargiulo Jun 12 '12 at 13:32
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&aquot; is NO substitute for ' as one's a single and the other a double. – RichardTheKiwi Jun 13 '12 at 23:46
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FYI: HTML5 does support both entities – Tarol Jun 09 '20 at 13:24
@RichardTheKiwi I assume you mean `"` - there is no such entity as `&aquot;` – Jake Aug 22 '21 at 00:30

score 46 · Answer 2 · answered Aug 31 '13 at 18:15

46

" is valid in both HTML5 and HTML4.

' is valid in HTML5, but not HTML4. However, most browsers support ' for HTML4 anyway.

answered Aug 31 '13 at 18:15

Zaz

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Note that IE 8 doesn't support `'`. – Paul D. Waite Sep 19 '13 at 09:50

score 35 · Answer 3 · edited Sep 19 '13 at 09:49

35

' is not part of the HTML 4 standard.

" is, though, so is fine to use.

edited Sep 19 '13 at 09:49

Paul D. Waite

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answered Jan 18 '10 at 03:36

Anon.

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How can this be an answer when &aquot; = " not '? It's like suggesting a colon for a semicolon... – RichardTheKiwi Jun 13 '12 at 23:45
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@Richardakacyberkiwi Read the question all the way to the end. – ColBeseder Aug 29 '12 at 08:38
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@Anon.: [`'` is now part of the HTML standard](http://www.whatwg.org/specs/web-apps/current-work/multipage/named-character-references.html#entity-apos). – Paul D. Waite Sep 19 '13 at 09:49
@RichardTheKiwi I assume you mean `"` - there is no such entity as `&aquot;` – Jake Aug 22 '21 at 00:31

R. Schreurs · Answer 4 · 2020-06-02T07:30:07.850

25

If you need to write semantically correct mark-up, even in HTML5, you must not use ' to escape single quotes. Although, I can imagine you actually meant apostrophe rather then single quote.

single quotes and apostrophes are not the same, semantically, although they might look the same.

Here's one apostrophe.

Use ' to insert it if you need HTML4 support. (edited)

In British English, single quotes are used like this:

"He told me to 'give it a try'", I said.

Quotes come in pairs. You can use:

<p><q>He told me to <q>give it a try</q></q>, I said.<p>

to have nested quotes in a semantically correct way, deferring the substitution of the actual characters to the rendering engine. This substitution can then be affected by CSS rules, like:

q {
  quotes: '"' '"' '<' '>';
}

An old but seemingly still relevant article about semantically correct mark-up: The Trouble With EM ’n EN (and Other Shady Characters).

(edited) This used to be:

Use ’ to insert it if you need HTML4 support.

But, as @James_pic pointed out, that is not the straight single quote, but the "Single curved quote, right".

edited Jun 02 '20 at 07:30

answered Dec 23 '14 at 15:57

R. Schreurs

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The question was clearly about using apostrophes and not quotes. Why would you post this? – Alex Skrypnyk Apr 21 '15 at 10:24
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I clearly see _single quote_ in the title. The question was why escaping them should not be done with _'_. I answered this because the support for ' is not the only concern. – R. Schreurs Apr 22 '15 at 19:46
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Single quotes are used that way in American English, also. – Rob_vH Feb 22 '16 at 06:24
This should be the accepted answer since it clarifies that apostrophe and single quotes aren't the same thing and that's why you shouldn't use apostrophes to enclose a HTML attribute value. – delroh Jul 04 '19 at 20:05
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In Unicode, the apostrophe character (') is classed as a quotation mark, and is the only form of the "straight" quotation mark in the spec. The advice to use ’ is at best incomplete, because that is the character for "Single curved quote, right". If you really are going for semantic correctness, it should be used for right quotation marks, while ‘ ("Single curved quote, left") should be used for left quotation marks. – James_pic May 31 '20 at 23:14
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Most of this answer has nothing to do with the question, which was about HTML markup syntax, not English grammar. – Jake Aug 22 '21 at 00:34

score 2 · Answer 5 · edited Nov 26 '13 at 17:00

2

If you really need single quotes, apostrophes, you can use

html    | numeric | hex
&lsquo; | &#145;  | &#x91; // for the left/beginning single-quote and
&rsquo; | &#146;  | &#x92; // for the right/ending single-quote

edited Nov 26 '13 at 17:00

hugomg

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answered Aug 28 '12 at 21:32

Jeff

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This doesn't answer the question(s) asked. – Jake Aug 22 '21 at 00:36

Why shouldn't `'` be used to escape single quotes?

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