Is there a good rule of thumb for when to use decimal vs. hexadecimal notation for HTML entities?
For example, a non-breaking hyphen is written in decimal as ‑ and in hex as ‑.
This answer says that hexadecimal is for Unicode; does that mean hex should be used if you're using the <meta charset="utf-8"> tag in the document <head>?
Occasionally, I will notice entity characters mistakenly rendered instead of the entities they represent -- for example, & appearing (instead of an ampersand) in an email subject line or RSS headline. Is either hex or decimal better for avoiding this?
One last consideration: can using hex or decimal affect the rendering clarity (crispness) of the character?
The rule of thumb is: use whichever you prefer, but prefer hex. ☺
There is no difference in meaning and no difference in browser support (the last browsers that supported decimal references only died in the 1990s).
As #AlexW describes, hexadecimal references are more natural than decimal, due to the way character code standards are written. But if you find decimal references more convenient, use them.
The issue has nothing to with meta tags and character encodings. The main reason why character references were introduced into HTML is that they let you enter characters quite independently of the encoding of the document. This includes characters that cannot be directly written at all in the encoding used. Thanks to them, you can enter any Unicode character even if the character encoding is ASCII or some other limited encoding, like ISO-8859-1.
In the old days, it was common to recommend the use of named references (or “entity references” as they are formally called in classic HTML), when possible, because a reference like Ω, when displayed literally to the user, is more understandable than a reference like Ω or Ω. This hasn’t been relevant for over a decade, as far as web browsers are considered. But e.g. e-mail clients might be kind of stupid^H^H^H^H^H^H^H^H^H underdeveloped in this respect. They might e.g. show references as such in a list of messages, even though they can intepret them properly when viewing a message. But there does not seem to be any consistent behavior that you could count on.
Overall
HTML (and XML) offers three ways to encode special characters: numeric hex &, numeric decimal & (aka "character references"), and named & (aka "entity references"). They've remained equally valid and fully supported by all major browsers for decades. They work with any encoding, but always render from the Unicode set (which is compatible with ASCII, ISO Latin, and Windows Latin, minus codes 128-159).
So it's up to personal preference, with a few things worth noting.
Necessity
If you add the proper charset meta tag to your HTML, you don't need to encode special characters at all (except & < > " ', or more generally, just & < in loose text). The exception is wanting to encode a character not present in the specified encoding. But if you use UTF-8, you can represent anything from Unicode anyway.
Brevity
For any character below index 10, decimal is shorter. A tab is 	, versus 	, so it may be worth it for pre tags containing a lot of TSV data, for example.
Ease of Use
Named references are the easiest to use and memorize, especially for code shared among developers of different backgrounds and skill sets. < is much more intuitive than <. As for someone else's comment regarding relevance, they're actually still fully supported as part of the W3C standard, and have even been expanded on for HTML5.
Best Practice
Using named or decimal references may not be the best general practice since the names are English-only, and unique to HTML (even XML lacks named references, minus the "big five"). Most programming languages and character tables use hex encoding, so it makes things easier and more portable in the long run when you stay consistent. Though for small projects or special cases, it may not really matter.
More info: http://xmlnews.org/docs/xml-basics.html#references
These are called numeric character references. They are derived from SGML and the numeric portion of them references the specific Unicode code point of the character you are trying to display. They allow you to represent characters of Unicode, even if the particular character set you wrote the HTML in doesn't have the character you are referencing. Whether you reference the code point with decimal or hexidecimal does not matter, except for very old browsers that prefer decimal. Hexidecimal support was added because Unicode code points are referenced in hex notation and it makes it much easier to look up the code point and then add the reference, without having to convert to decimal:
U+007D
=
}
To answer your question:
This answer says that hexadecimal is for Unicode; does that mean hex
should be used if you're using the <meta charset="utf-8"> tag in the
document ?
You have to understand that UTF-8 is backwards-compatible with ASCII / ISO-8859-1. So the first 256 characters of UTF-8 will be the same in ASCII and UTF-8. Hex is just easier for UTF-8 because, as of 2013 there are 1,114,112 Unicode code points. So it's easier to write � than it is to write � etc.
Related
I'm trying to get special characters into HTML, and am not sure if this is even possible. If anyone remembers Kroz, or just about every DOS interface - there is a special set of shape characters. I'm wanting to use the single braces, double braces, shadows, and other shape characters, but I can't seem to track any of these down anywhere.
Also, will using these characters in an HTML environment present any localization concerns / will there be a required charset?
Thanks!
There is no “extended ASCII”; ASCII ends at code position 127 decimal, 7F hexadecimal. What is called “extended ASCII” is a set of mutually incompatible 8-bit encodings that contain the printable ASCII characters in the same positions as in ASCII. In your case, you seem to want to use the Code Page 437. All of its characters exist in Unicode. You can find the correspondence at
http://en.wikipedia.org/wiki/Code_page_437
which I believe to be correct in this issue; but the authoritative reference is
http://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/PC/CP437.TXT
There are various ways to enter the characters. You can use, say, “▓” as such in HTML, if you have some way of entering it and you use UTF-8 on the page. Alternatively, you can use character references like ▓.
Yes, similar characters exist in the UTF-8 character set. These are called box drawing characters.
See: http://www.fileformat.info/info/unicode/block/box_drawing/utf8test.htm
I have a question about ASCII code and HTML.
Most sites state what ASCII is but then mention things like HTML alternative or HTML code. Is this still ASCII?
Any way, my actual question is, is < ASCII (if not, what 'language' is it)?
ASCII is an encoding : it defines how the char you see are encoded in 0 & 1 (in fact in bytes). This problem is totally unrelated to how a browser displays the characters it decodes in a HTML file.
You can send to a browser a file containing the characters < in any encoding, be it UTF-8, ASCII, or another one.
< is a character entity reference, coming from SGML and defined both in XML and HTML.
Here's the official reference about HTML4 character entities.
< is an HTML entity. Html entities are used when a character cannot be safely used within the browser. For example if you wanted to use a less than sign within the content of your page, using < would get interpreted by the browser as the start of a new tag. Using an html entity tells the browser to render the actual character and not read it as the start of a tag.
http://www.w3schools.com/html/html_entities.asp
The notation < consists of four characters, which all have a representation in the ASCII character code, but that’s immaterial. In HTML (as well as in SGML and XML), the notation denotes the LESS-THAN character “<”, in most contexts. The “<” character, too, has a representation in ASCII, but this too is immaterial.
People often use the expression “ASCII character” to denote a character that has a representation in ASCII, i.e. an ASCII code. In reality, the characters need not be ASCII encoded. But the concept “ASCII character” is still useful for some practical purposes. And using it, we can say that < is a sequence of ASCII characters that denotes an ASCII character.
The “language” here is really a set of markup languages in which some sequences of ASCII characters are defined to mean certain (ASCII or non-ASCII) characters.
The need for using < (when you wish to include “<” as text content) stems from the principle that in most contexts in HTML, the “<” character starts a tag, instead of being taken as such.
Things like < are called entity references in SGML tradition, though in HTML contexts often prefixed with the word character to emphasize that the predefined entities of HTML all evaluate to single characters. The HTML5 drafts, abandoning the SGML tradition, use the term named character references instead.
Any way, my actual question is, is < ASCII (if not, what 'language'
is it)?
They are called entities and are part of HTML.
I'm making a static HTML page that displays courtesy text in multiple languages. I noticed that if I paste ウェブサイトのメンテナンスの下で into Expression Blend, that text appears the same in the code. I think it's bad for compatibility and should be replaced by proper HTML entities.
I have tried http://www.opinionatedgeek.com/DotNet/Tools/HTMLEncode/encode.aspx but it returns me the same Japanese text.
Is it correct, from the point of view of browser compatibility, to paste that Japanese right into the source code of an HTML page?
Else, what is the correct HTML encoding of that text? Or, better, is there any tool that I can use to convert non-ASCII characters to HTML entities, possibly online and possibly free?
I think it's bad for compatibility and should be replaced by proper
HTML entities.
Quite the opposite actually, your preference should be to not use html entities but rather correctly declare document encoding as UTF-8 and use the actual characters. There are quite a few compelling reasons to do so, but the real question is why not use it since it's a well- and widely supported standard?
Some of those points have been summarised previously:
UTF-8 encodings are easier to read and edit for those who understand
what the character means and know how to type it.
UTF-8 encodings are just as unintelligible as HTML entity encodings
for those who don't understand them, but they have the advantage of
rendering as special characters rather than hard to understand decimal
or hex encodings.
[For example] Wikipedia... actually go through articles and convert
character entities to their corresponding real characters for the sake
of user-friendliness and searchability.
As long as you mark your web-page as UTF-8, either in the http headers or the meta tags, having foreign characters in your web-pages should be a non-issue. Alternately you could encode/decode these strings using encodeURI/decodeURI functions in JavaScript
encodeURI('ウェブサイトのメンテナンスの下で')
//returns"%E3%82%A6%E3%82%A7%E3%83%96%E3%82%B5%E3%82%A4%E3%83%88%E3%81%AE%E3%83%A1%E3%83%B3%E3%83%86%E3%83%8A%E3%83%B3%E3%82%B9%E3%81%AE%E4%B8%8B%E3%81%A7"
decodeURI("%E3%82%A6%E3%82%A7%E3%83%96%E3%82%B5%E3%82%A4%E3%83%88%E3%81%AE%E3%83%A1%E3%83%B3%E3%83%86%E3%83%8A%E3%83%B3%E3%82%B9%E3%81%AE%E4%B8%8B%E3%81%A7")
//returns ウェブサイトのメンテナンスの下で
If you are looking for a tool to convert a bunch of static strings to unicode characters, you could simply use encodeURI/decodeURI functions from a web-page developer console (firebug for mozilla/firefox). Hope this helps!
HTML entities are only useful if you need to represent a character that cannot be represented in the encoding your document is saved in. For example, ASCII has no specification for how to represent "€". If you want to use that character in an ASCII encoded HTML document, you have to encode it as € or not use it at all.
If you are using a character encoding for your document that can represent all the characters you need though, like UTF-8, there's no need for HTML entities. You simply need to make sure the browser knows what encoding the document is in so it can interpret it correctly. This is really the preferable method, since it simply keeps the source code readable. It really makes no sense to want to work with HTML entities if you can simply work with the actual characters.
See http://kunststube.net/frontback for some more information.
When I copy/paste text from most sites and pdfs, the following characters are almost always in the unicode equivalent:
double quote: " is “ and ” (“ and ”)
single quote: ' is ‘ and ’ (‘ and ’)
ellipsis: ... is … (…)
I understand ones that can't be represented without unicode like © and ¢, but even for those, I wonder.
When should you use these unicode equivalents? Are they more semantic than not using them? Are they better interpreted by devices (copy/paste/print)? I always find it annoying getting those quote and ellipsis characters because with textmate + programming, you don't use them.
When should you use these unicode equivalents? Are they more semantic than not using them?
Note that these are not “unicode equivalents”. Those characters are available in many character sets other than Unicode, and they are strictly distinct from the alternatives that you propose.
In typography, the left and right versions of the single and double quotation marks are correct. They provide the traditional appearance for those characters that has been used in print media for many years. The ellipsis character provides the correct spacing for an ellipsis that does not naturally occur when using consecutive full stop characters. So the reason all of these are used is to make the text appear correctly to human readers.
Are they better interpreted by devices (copy/paste/print)?
Any system that uses any character set should be designed to correctly handle that character set. If the text is encoded in Unicode, then any recent system (from the last 15 years at least) should be able to handle it, since Unicode is the de facto standard character set for all modern systems.
Not all Unicode-conformant systems will be able to display all characters correctly. This will depend on the fonts available, and even the rendering system that uses the fonts. But any Unicode-conformant system will be able to transmit the characters unaltered (such as in a copy and paste operation).
I always find it annoying getting those quote and ellipsis characters because with textmate + programming, you don't use them.
It is unusual to copy English (or whatever language) text directly into a program without having to add separate delimiters to that text. But most modern programming languages will not have any difficulty handling the text once it is property delimited.
Any systems that cannot handle Unicode correctly should be updated. Legacy character encodings will have no place in the future.
I think there's a simple explanation: MS Word converts these characters/sequences automatically as you type and a lot of text in the internet has been copied from this text editor.
Most of the articles I get for my site from other authors are sent as .doc file and I have to convert it. Usually, it contains these characters you've mentioned.
I'd also add one more: many different types of dashes instead of the hyphen. And also the low opening double quote (as seen in some european languages).
I usually let them stay in the text (all my pages are unicode). It's just important to remember it when playing around with regex etc (especially the dashes can be tricky and hard to spot).
HTML entities serve a triple purpose:
Being able to use characters that do not belong to the document character set, e.g., insert an euro symbol in a ISO-8859-1 document.
Escape characters that have a special meaning in HTML, such as angle brackets.
Make it easier to type characters that are not in your keyboard or are not supported by your editor, e.g. a copyright symbol.
Update:
My info is correct but I suspect I've answered the wrong question...
On the web, I would consider that markup adds semantic meaning, content does not. So it doesn't really matter which you use in this context.
Typographers would insist on “ and ”, where programmers don't care and just use regular old quotes ".
The key here is interoperability. There are different encoding schemes. As we've all been victim to, people paste content into an editor from WORD, which uses windows-1251 encoding. When you serve this content up via AJAX is usually breaks because AJAX uses UTF-8 encoding by default.
Office 2010 now allows for the saving of documents in UTF-8 format. Also, databases have different unicode encoding schemes. The best bet is to use UTF-8 end-to-end.
When you copy-pasta text that includes special characters, they will be left as they are. This is perfectly fine if the characters match the charset used by the webpage.
HTML entities are just a convenience for producing specific characters in any character set. Keyboards tend not to have keys to get symbols like ©, so the HTML entity is a shortcut.
I'm going to generalize and say that most of the time the content is UTF-8 (please correct me if I'm wrong). The copied characters are usually copied correctly and everything works great, if they aren't copied correctly, or the charset is subject to change, or you're after i18n support, go with the HTML or XML entities. Otherwise, leave them as they are, the browser will display them just fine.
This has been confusing me for some time. With the advent of UTF-8 as the de-facto standard in web development I'm not sure in which situations I'm supposed to use the HTML entities and for which ones should I just use the UTF-8 character. For example,
em dash (–, &emdash;)
ampersand (&, &)
3/4 fraction (¾, ¾)
Please do shed light on this issue. It will be appreciated.
Based on the comments I have received, I looked into this a little further. It seems that currently the best practice is to forgo using HTML entities and use the actual UTF-8 character instead. The reasons listed are as follows:
UTF-8 encodings are easier to read and edit for those who understand what the character means and know how to type it.
UTF-8 encodings are just as unintelligible as HTML entity encodings for those who don't understand them, but they have the advantage of rendering as special characters rather than hard to understand decimal or hex encodings.
As long as your page's encoding is properly set to UTF-8, you should use the actual character instead of an HTML entity. I read several documents about this topic, but the most helpful were:
UTF-8: The Secret of Character Encoding
Wikipedia Special Characters Help
From the UTF-8: The Secret of Character Encoding article:
Wikipedia is a great case study for an
application that originally used
ISO-8859-1 but switched to UTF-8 when
it became far too cumbersome to support
foreign languages. Bots will now
actually go through articles and
convert character entities to their
corresponding real characters for the
sake of user-friendliness and
searchability.
That article also gives a nice example involving Chinese encoding. Here is the abbreviated example for the sake of laziness:
UTF-8:
這兩個字是甚麼意思
HTML Entities:
這兩個字是甚麼意思
The UTF-8 and HTML entity encodings are both meaningless to me, but at least the UTF-8 encoding is recognizable as a foreign language, and it will render properly in an edit box. The article goes on to say the following about the HTML entity-encoded version:
Extremely inconvenient for those of us
who actually know what character
entities are, totally unintelligible
to poor users who don't! Even the
slightly more user-friendly,
"intelligible" character entities like
θ will leave users who are
uninterested in learning HTML
scratching their heads. On the other
hand, if they see θ in an edit box,
they'll know that it's a special
character, and treat it accordingly,
even if they don't know how to write
that character themselves.
As others have noted, you still have to use HTML entities for reserved XML characters (ampersand, less-than, greater-than).
You don't generally need to use HTML character entities if your editor supports Unicode. Entities can be useful when:
Your keyboard does not support the character you need to type. For example, many keyboards do not have em-dash or the copyright symbol.
Your editor does not support Unicode (very common some years ago, but probably not today).
You want to make it explicit in the source what is happening. For example, the code is clearer than the corresponding white space character.
You need to escape HTML special characters like <, &, or ".
Entities may buy you some compatibility with brain-dead clients that don't understand encodings correctly. I don't believe that includes any current browsers, but you never know what other kinds of programs might be hitting you up.
More useful, though, is that HTML entities protect you from your own errors: if you misconfigure something on the server and you end up serving a page with an HTTP header that says it's ISO-8859-1 and a META tag that says it's UTF-8, at least your —es will always work.
I would not use UTF-8 for characters that are easily confused visually. For example, it is difficult to distinguish an emdash from a minus, or especially a non-breaking space from a space. For these characters, definitely use entities.
For characters that are easily understood visually (such as the chinese examples above), go ahead and use UTF-8 if you like.
Personally I do everything in utf-8 since a long time, however, in an html page, you always need to convert ampersands (&), greater than (>) and lesser then (<) characters to their equivalent entities, &, > and <
Also, if you intend on doing some programming using utf-8 text, there are a few thing to watch for.
XML needs some extra lines to validate when using entities.
Some libraries do not play along nice with utf-8. For instance, PHP in some Linux distributions dropped full support for utf-8 in their regular expression libraries.
It is harder to limit the number of characters in a text that uses html entities, because a single entity uses many characters. Also there's always the risk of cutting the entity in half.
HTML entities are useful when you want to generate content that is going to be included (dynamically) into pages with (several) different encodings. For example, we have white label content that is included both into ISO-8859-1 and UTF-8 encoded web pages...
If character set conversion from/to UTF-8 wasn't such a big unreliable mess (you always stumble over some characters and some tools that don't convert properly), standardizing on UTF-8 would be the way to go.
If your pages are correctly encoded in utf-8 you should have no need for html entities, just use the characters you want directly.
All of the previous answers make sense to me.
In addition: It mostly depends on the editor you intent to use and the document language. As a minimum requirement for the editor is that it supports the document language. That means, that if your text is in japanese, beware of using an editor which does not show them (i.e. no entities for the document itself). If its english, you can even use an old vim-like editor and use entities only for the relative seldom © and friends.
Of course: > for > and other HTML-specials still need escapes.
But even with the other latin-1 languages (german, french etc.) writing ä is a pain in you know where...
In addition, I personally write entities for invisible characters and those which are looking similar to standard-ascii and are therefore easily confused. For example, there is u1173 (looking like a dash in some charsets) or u1175, which looks like the vertical bar. I'd use entities for those in any case.