Why don t self-closing script elements work

Question

What is the reason browsers do not correctly recognize    lt script src  foobar js    gt   lt  -- self-closing script element -- gt    Only this is recognized    lt script src  foobar js  gt  lt  script gt    Does this break the concept of XHTML support   Note  This statement is correct at least for all IE  6-8 beta 2

User · Answer

Internet Explorer 8 and older don t support the proper MIME type for XHTML  application xhtml xml  If you re serving XHTML as text html  which you have to for these older versions of Internet Explorer to do anything  it will be interpreted as HTML 4 01  You can only use the short syntax with any element that permits the closing tag to be omitted  See the HTML 4 01 Specification  The XML  short form  is interpreted as an attribute named    which  because there is no equals sign  is interpreted as having an implicit value of  quot   quot   This is strictly wrong in HTML 4 01 - undeclared attributes are not permitted - but browsers will ignore it  IE9 and later support XHTML 5 served with application xhtml xml

User · Answer

That s because SCRIPT TAG is not a VOID ELEMENT   In an HTML Document - VOID ELEMENTS do not need a  closing tag  at all   In xhtml  everything is Generic  therefore they all need termination e g  a  closing tag   Including br  a simple line-break  as  lt br gt  lt  br gt  or its shorthand  lt br   gt    However  a Script Element is never a void or a parametric Element  because script tag before anything else  is a Browser Instruction  not a Data Description declaration   Principally  a Semantic Termination Instruction e g   a  closing tag  is only needed for processing instructions who s semantics cannot be terminated by a succeeding tag  For instance     lt H1 gt  semantics cannot be terminated by a following  lt P gt  because it doesn t carry enough of its own semantics to override and therefore terminate the previous H1 instruction set  Although it will be able to break the stream into a new paragraph line  it is not  strong enough  to override the present font size  amp  style line-height pouring down the stream  i e leaking from H1  because P doesn t have it     This is how and why the      termination  signalling has been invented    A generic no-description termination Tag like  lt    gt   would have sufficed for any single fall off the encountered cascade  e g    lt H1 gt Title lt    gt  but that s not always the case  because we also want to be capable of  nesting   multiple intermediary tagging of the Stream  split into torrents before wrapping   falling onto another cascade  As a consequence a generic terminator such as  lt    gt  would not be able to determine the target of a property to terminate  For example   lt b gt bold  lt i gt bold-italic  lt    gt  italic  lt   gt normal  Would undoubtedly fail to get our intention right and would most probably interpret it as bold bold-itallic bold normal   This is how the notion of a wrapper ie   container was born   These notions are so similar that it is impossible to discern and sometimes the same element may have both   lt H1 gt  is both wrapper and container at the same time  Whereas  lt B gt  only a semantic wrapper   We ll need a plain  no semantics container  And of course the invention of a DIV Element came by    The DIV element is actually a 2BR-Container  Of course the coming of CSS made the whole situation weirder than it would otherwise have been and caused a great confusion with many great consequences - indirectly   Because with CSS you could easily override the native pre amp after BR behavior of a newly invented DIV  it is often referred to  as a  do nothing container   Which is  naturally wrong  DIVs are block elements and will natively break the line of the stream both before and after the end signalling  Soon the WEB started suffering from page DIV-itis  Most of them still are   The coming of CSS with its capability to fully override and completely redefine the native behavior of any HTML Tag  somehow managed to confuse and blur the whole meaning of HTML existence     Suddenly all HTML tags appeared as if obsolete  they were defaced  stripped of all their original meaning  identity and purpose  Somehow you d gain the impression that they re no longer needed  Saying  A single container-wrapper tag would suffice for all the data presentation  Just add the required attributes  Why not have meaningful tags instead  Invent tag names as you go and let the CSS bother with the rest   This is how xhtml was born and of course the great blunt  paid so dearly by new comers and a distorted vision of what is what  and what s the damn purpose of it all  W3C went from World Wide Web to What Went Wrong  Comrades     The purpose of HTML is to stream meaningful data to the human recipient   To deliver Information   The formal part is there to only assist the clarity of information delivery  xhtml doesn t give the slightest consideration to the information  - To it  the information is absolutely irrelevant   The most important thing in the matter is to know and be able to understand that xhtml is not just a version of some extended HTML  xhtml is a completely different beast  grounds up  and therefore it is wise to keep them separate

User · Answer

Difference between  true XHTML    faux XHTML  and HTML as well as importance of the server-sent MIME type had been already described here well  If you want to try it out right now  here is simple editable snippet with live preview including self-closed script tag for capable browsers    x000D   x000D  div   display  flex    x000D  div   div  flex-direction  column    x000D   lt div gt Mime type   lt label gt  lt input type  radio  onchange  t onkeyup    id  x  checked  name  mime  gt  application xhtml xml lt  label gt  x000D   lt label gt  lt input type  radio  onchange  t onkeyup    name  mime  gt  text html lt  label gt  lt  div gt  x000D   lt div gt  lt textarea id  t  rows  4   x000D  onkeyup  i src  data    x checked  application xhtml xml   text html       encodeURIComponent t value   x000D   gt  lt  xml version  1 0   gt  x000D   lt  DOCTYPE html PUBLIC  -  W3C  DTD XHTML 1 0 Strict  EN   http   www w3 org TR xhtml1 DTD xhtml1-strict dtd  x000D    lt  ENTITY x  true XHTML  gt   gt  x000D   lt html xmlns  http   www w3 org 1999 xhtml  gt  x000D   lt body gt  x000D     lt p gt  x000D       lt span id  greet  swapto  Hello  gt Hell  NO    lt  span gt   amp x   x000D       lt script src  data text javascript  g document getElementById  greet    innerText g getAttribute  swapto      gt  x000D      Nice to meet you  x000D       lt  --  x000D        Previous text node and all further content falls into SCRIPT element content in text html mode  so is not rendered  Because no end script tag is found  no script runs in text html x000D      -- gt  x000D     lt  p gt  x000D   lt  body gt  x000D   lt  html gt  lt  textarea gt  x000D   x000D   lt iframe id  i  height  80  gt  lt  iframe gt  x000D   x000D   lt script gt t onkeyup   lt  script gt  x000D   lt  div gt  x000D   x000D   x000D    You should see Hello  true XHTML  Nice to meet you  below textarea   For incapable browsers you can copy content of the textarea and save it as a file with  xhtml  or  xht  extension  thanks Alek for this hint

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XHTML 1 specification says     3  Element Minimization and Empty Element Content     Given an empty instance of an element whose content model is not EMPTY  for example  an empty title or paragraph  do not use the minimized form  e g  use  lt p gt   lt  p gt  and not  lt p   gt      XHTML DTD specifies script elements as    lt  -- script statements  which may include CDATA sections -- gt   lt  ELEMENT script   PCDATA  gt

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Internet Explorer 8 and earlier do not support XHTML parsing  Even if you use an XML declaration and or an XHTML doctype  old IE still parse the document as plain HTML  And in plain HTML  the self-closing syntax is not supported  The trailing slash is just ignored  you have to use an explicit closing tag  Even browsers with support for XHTML parsing  such as IE 9 and later  will still parse the document as HTML unless you serve the document with a XML content type  But in that case old IE will not display the document at all

User · Answer

Internet Explorer 8 and older don t support the proper MIME type for XHTML  application xhtml xml  If you re serving XHTML as text html  which you have to for these older versions of Internet Explorer to do anything  it will be interpreted as HTML 4 01  You can only use the short syntax with any element that permits the closing tag to be omitted  See the HTML 4 01 Specification  The XML  short form  is interpreted as an attribute named    which  because there is no equals sign  is interpreted as having an implicit value of  quot   quot   This is strictly wrong in HTML 4 01 - undeclared attributes are not permitted - but browsers will ignore it  IE9 and later support XHTML 5 served with application xhtml xml

User · Answer

Internet Explorer 8 and older don t support the proper MIME type for XHTML  application xhtml xml  If you re serving XHTML as text html  which you have to for these older versions of Internet Explorer to do anything  it will be interpreted as HTML 4 01  You can only use the short syntax with any element that permits the closing tag to be omitted  See the HTML 4 01 Specification  The XML  short form  is interpreted as an attribute named    which  because there is no equals sign  is interpreted as having an implicit value of  quot   quot   This is strictly wrong in HTML 4 01 - undeclared attributes are not permitted - but browsers will ignore it  IE9 and later support XHTML 5 served with application xhtml xml

User · Answer

Simply modern answer is because the tag is denoted as mandatory that way     Tag omission  None  both the starting and ending tag are mandatory    https   developer mozilla org en-US docs Web HTML Element script

User · Answer

Difference between  true XHTML    faux XHTML  and HTML as well as importance of the server-sent MIME type had been already described here well  If you want to try it out right now  here is simple editable snippet with live preview including self-closed script tag for capable browsers    x000D   x000D  div   display  flex    x000D  div   div  flex-direction  column    x000D   lt div gt Mime type   lt label gt  lt input type  radio  onchange  t onkeyup    id  x  checked  name  mime  gt  application xhtml xml lt  label gt  x000D   lt label gt  lt input type  radio  onchange  t onkeyup    name  mime  gt  text html lt  label gt  lt  div gt  x000D   lt div gt  lt textarea id  t  rows  4   x000D  onkeyup  i src  data    x checked  application xhtml xml   text html       encodeURIComponent t value   x000D   gt  lt  xml version  1 0   gt  x000D   lt  DOCTYPE html PUBLIC  -  W3C  DTD XHTML 1 0 Strict  EN   http   www w3 org TR xhtml1 DTD xhtml1-strict dtd  x000D    lt  ENTITY x  true XHTML  gt   gt  x000D   lt html xmlns  http   www w3 org 1999 xhtml  gt  x000D   lt body gt  x000D     lt p gt  x000D       lt span id  greet  swapto  Hello  gt Hell  NO    lt  span gt   amp x   x000D       lt script src  data text javascript  g document getElementById  greet    innerText g getAttribute  swapto      gt  x000D      Nice to meet you  x000D       lt  --  x000D        Previous text node and all further content falls into SCRIPT element content in text html mode  so is not rendered  Because no end script tag is found  no script runs in text html x000D      -- gt  x000D     lt  p gt  x000D   lt  body gt  x000D   lt  html gt  lt  textarea gt  x000D   x000D   lt iframe id  i  height  80  gt  lt  iframe gt  x000D   x000D   lt script gt t onkeyup   lt  script gt  x000D   lt  div gt  x000D   x000D   x000D    You should see Hello  true XHTML  Nice to meet you  below textarea   For incapable browsers you can copy content of the textarea and save it as a file with  xhtml  or  xht  extension  thanks Alek for this hint

User · Answer

XHTML 1 specification says     3  Element Minimization and Empty Element Content     Given an empty instance of an element whose content model is not EMPTY  for example  an empty title or paragraph  do not use the minimized form  e g  use  lt p gt   lt  p gt  and not  lt p   gt      XHTML DTD specifies script elements as    lt  -- script statements  which may include CDATA sections -- gt   lt  ELEMENT script   PCDATA  gt

User · Answer

Internet Explorer 8 and earlier do not support XHTML parsing  Even if you use an XML declaration and or an XHTML doctype  old IE still parse the document as plain HTML  And in plain HTML  the self-closing syntax is not supported  The trailing slash is just ignored  you have to use an explicit closing tag  Even browsers with support for XHTML parsing  such as IE 9 and later  will still parse the document as HTML unless you serve the document with a XML content type  But in that case old IE will not display the document at all

User · Answer

To add to what Brad and squadette have said  the self-closing XML syntax  lt script   gt  actually is correct XML  but for it to work in practice  your web server also needs to send your documents as properly formed XML with an XML mimetype like application xhtml xml in the HTTP Content-Type header  and not as text html    However  sending an XML mimetype will cause your pages not to be parsed by IE7  which only likes text html   From w3      In summary   application xhtml xml    SHOULD be used for XHTML Family   documents  and the use of  text html    SHOULD be limited to HTML-compatible   XHTML 1 0 documents   application xml    and  text xml  MAY also be used  but   whenever appropriate     application xhtml xml  SHOULD be used   rather than those generic XML media   types    I puzzled over this a few months ago  and the only workable  compatible with FF3  and IE7  solution was to use the old  lt script gt  lt  script gt  syntax with text html  HTML syntax   HTML mimetype    If your server sends the text html type in its HTTP headers  even with otherwise properly formed XHTML documents  FF3  will use its HTML rendering mode which means that  lt script   gt  will not work  this is a change  Firefox was previously less strict    This will happen regardless of any fiddling with http-equiv meta elements  the XML prolog or doctype inside your document -- Firefox branches once it gets the text html header  that determines whether the HTML or XML parser looks inside the document  and the HTML parser does not understand  lt script   gt

User · Answer

Internet Explorer 8 and older don t support the proper MIME type for XHTML  application xhtml xml  If you re serving XHTML as text html  which you have to for these older versions of Internet Explorer to do anything  it will be interpreted as HTML 4 01  You can only use the short syntax with any element that permits the closing tag to be omitted  See the HTML 4 01 Specification  The XML  short form  is interpreted as an attribute named    which  because there is no equals sign  is interpreted as having an implicit value of  quot   quot   This is strictly wrong in HTML 4 01 - undeclared attributes are not permitted - but browsers will ignore it  IE9 and later support XHTML 5 served with application xhtml xml

User · Answer

Unlike XML and XHTML  HTML has no knowledge of the self-closing syntax   Browsers that interpret XHTML as HTML don t know that the   character indicates that the tag should be self-closing  instead they interpret it like an empty attribute and the parser still thinks the tag is  open    Just as  lt script defer gt  is treated as  lt script defer  defer  gt    lt script   gt  is treated as  lt script       gt

User · Answer

Unlike XML and XHTML  HTML has no knowledge of the self-closing syntax   Browsers that interpret XHTML as HTML don t know that the   character indicates that the tag should be self-closing  instead they interpret it like an empty attribute and the parser still thinks the tag is  open    Just as  lt script defer gt  is treated as  lt script defer  defer  gt    lt script   gt  is treated as  lt script       gt

User · Answer

In case anyone s curious  the ultimate reason is that HTML was originally a dialect of SGML  which is XML s weird older brother  In SGML-land  elements can be specified in the DTD as either self-closing  e g  BR  HR  INPUT   implicitly closeable  e g  P  LI  TD   or explicitly closeable  e g  TABLE  DIV  SCRIPT   XML  of course  has no concept of this   The tag-soup parsers used by modern browsers evolved out of this legacy  although their parsing model isn t pure SGML anymore  And of course  your carefully-crafted XHTML is being treated as badly-written SGML-inspired tag-soup unless you send it with an XML mime type  This is also why      lt p gt  lt div gt hello lt  div gt  lt  p gt       gets interpreted by the browser as    lt p gt  lt  p gt  lt div gt hello lt  div gt  lt p gt  lt  p gt       which is the recipe for a lovely obscure bug that can throw you into fits as you try to code against the DOM

User · Answer

That s because SCRIPT TAG is not a VOID ELEMENT   In an HTML Document - VOID ELEMENTS do not need a  closing tag  at all   In xhtml  everything is Generic  therefore they all need termination e g  a  closing tag   Including br  a simple line-break  as  lt br gt  lt  br gt  or its shorthand  lt br   gt    However  a Script Element is never a void or a parametric Element  because script tag before anything else  is a Browser Instruction  not a Data Description declaration   Principally  a Semantic Termination Instruction e g   a  closing tag  is only needed for processing instructions who s semantics cannot be terminated by a succeeding tag  For instance     lt H1 gt  semantics cannot be terminated by a following  lt P gt  because it doesn t carry enough of its own semantics to override and therefore terminate the previous H1 instruction set  Although it will be able to break the stream into a new paragraph line  it is not  strong enough  to override the present font size  amp  style line-height pouring down the stream  i e leaking from H1  because P doesn t have it     This is how and why the      termination  signalling has been invented    A generic no-description termination Tag like  lt    gt   would have sufficed for any single fall off the encountered cascade  e g    lt H1 gt Title lt    gt  but that s not always the case  because we also want to be capable of  nesting   multiple intermediary tagging of the Stream  split into torrents before wrapping   falling onto another cascade  As a consequence a generic terminator such as  lt    gt  would not be able to determine the target of a property to terminate  For example   lt b gt bold  lt i gt bold-italic  lt    gt  italic  lt   gt normal  Would undoubtedly fail to get our intention right and would most probably interpret it as bold bold-itallic bold normal   This is how the notion of a wrapper ie   container was born   These notions are so similar that it is impossible to discern and sometimes the same element may have both   lt H1 gt  is both wrapper and container at the same time  Whereas  lt B gt  only a semantic wrapper   We ll need a plain  no semantics container  And of course the invention of a DIV Element came by    The DIV element is actually a 2BR-Container  Of course the coming of CSS made the whole situation weirder than it would otherwise have been and caused a great confusion with many great consequences - indirectly   Because with CSS you could easily override the native pre amp after BR behavior of a newly invented DIV  it is often referred to  as a  do nothing container   Which is  naturally wrong  DIVs are block elements and will natively break the line of the stream both before and after the end signalling  Soon the WEB started suffering from page DIV-itis  Most of them still are   The coming of CSS with its capability to fully override and completely redefine the native behavior of any HTML Tag  somehow managed to confuse and blur the whole meaning of HTML existence     Suddenly all HTML tags appeared as if obsolete  they were defaced  stripped of all their original meaning  identity and purpose  Somehow you d gain the impression that they re no longer needed  Saying  A single container-wrapper tag would suffice for all the data presentation  Just add the required attributes  Why not have meaningful tags instead  Invent tag names as you go and let the CSS bother with the rest   This is how xhtml was born and of course the great blunt  paid so dearly by new comers and a distorted vision of what is what  and what s the damn purpose of it all  W3C went from World Wide Web to What Went Wrong  Comrades     The purpose of HTML is to stream meaningful data to the human recipient   To deliver Information   The formal part is there to only assist the clarity of information delivery  xhtml doesn t give the slightest consideration to the information  - To it  the information is absolutely irrelevant   The most important thing in the matter is to know and be able to understand that xhtml is not just a version of some extended HTML  xhtml is a completely different beast  grounds up  and therefore it is wise to keep them separate

User · Answer

The people above have already pretty much explained the issue  but one thing that might make things clear is that  though people use  lt br  gt  and such all the time in HTML documents  any   in such a position is basically ignored  and only used when trying to make something both parseable as XML and HTML  Try  lt p  gt foo lt  p gt   for example  and you get a regular paragraph

User · Answer

Simply modern answer is because the tag is denoted as mandatory that way     Tag omission  None  both the starting and ending tag are mandatory    https   developer mozilla org en-US docs Web HTML Element script

User · Answer

Others have answered  how  and quoted spec  Here is the real story of  why no  lt script  gt    after many hours digging into bug reports and mailing lists     HTML 4  HTML 4 is based on SGML   SGML has some shorttags  such as  lt BR     lt B gt text lt   gt    lt B text   or  lt OL lt LI gt item lt  LI lt  OL gt   XML takes the first form  redefines the ending as      SGML is flexible   so that it becomes  lt BR  gt    However  HTML did not redfine  so  lt SCRIPT  gt  should mean  lt SCRIPT gt  gt     Yes  the     should be part of content  and the tag is still not closed    Obviously  this is incompatible with XHTML and will break many sites  by the time browsers were mature enough to care about this   so nobody implemented shorttags and the specification advises against them   Effectively  all  working  self-ended tags are tags with prohibited end tag on technically non-conformant parsers and are in fact invalid  It was W3C which came up with this hack to help transitioning to XHTML by making it HTML-compatible   And  lt script gt  s end tag is not prohibited    Self-ending  tag is a hack in HTML 4 and is meaningless     HTML 5  HTML5 has five types of tags and only  void  and  foreign  tags are allowed to be self-closing   Because  lt script gt  is not void  it may have content  and is not foreign  like MathML or SVG    lt script gt  cannot be self-closed  regardless of how you use it   But why  Can t they regard it as foreign  make special case  or something   HTML 5 aims to be backward-compatible with implementations of HTML 4 and XHTML 1  It is not based on SGML or XML  its syntax is mainly concerned with documenting and uniting the implementations   This is why  lt br  gt   lt hr  gt  etc  are valid HTML 5 despite being invalid HTML4    Self-closing  lt script gt  is one of the tags where implementations used to differ  It used to work in Chrome  Safari  and Opera  to my knowledge it never worked in Internet Explorer or Firefox   This was discussed when HTML 5 was being drafted and got rejected because it breaks browser compatibility  Webpages that self-close script tag may not render correctly  if at all  in old browsers  There were other proposals  but they can t solve the compatibility problem either   After the draft was released  WebKit updated the parser to be in conformance   Self-closing  lt script gt  does not happen in HTML 5 because of backward compatibility to HTML 4 and XHTML 1     XHTML 1   XHTML 5  When really served as XHTML   lt script  gt  is really closed  as other answers have stated   Except that the spec says it should have worked when served as HTML      XHTML Documents     may be labeled with the Internet Media Type  text html   RFC2854   as they are compatible with most HTML browsers    So  what happened   People asked Mozilla to let Firefox parse conforming documents as XHTML regardless of the specified content header  known as content sniffing   This would have allowed self-closing scripts  and content sniffing was necessary anyway because web hosters were not mature enough to serve the correct header  IE was good at it   If the first browser war didn t end with IE 6  XHTML may have been on the list  too  But it did end  And IE 6 has a problem with XHTML  In fact IE did not support the correct MIME type at all  forcing everyone to use text html for XHTML because IE held major market share for a whole decade   And also content sniffing can be really bad and people are saying it should be stopped   Finally  it turns out that the W3C didn t mean XHTML to be sniffable  the document is both  HTML and XHTML  and Content-Type rules  One can say they were standing firm on  just follow our spec  and ignoring what was practical  A mistake that continued into later XHTML versions   Anyway  this decision settled the matter for Firefox  It was 7 years before Chrome was born  there were no other significant browser  Thus it was decided   Specifying the doctype alone does not trigger XML parsing because of following specifications

User · Answer

Unlike XML and XHTML  HTML has no knowledge of the self-closing syntax   Browsers that interpret XHTML as HTML don t know that the   character indicates that the tag should be self-closing  instead they interpret it like an empty attribute and the parser still thinks the tag is  open    Just as  lt script defer gt  is treated as  lt script defer  defer  gt    lt script   gt  is treated as  lt script       gt

User · Answer

In case anyone s curious  the ultimate reason is that HTML was originally a dialect of SGML  which is XML s weird older brother  In SGML-land  elements can be specified in the DTD as either self-closing  e g  BR  HR  INPUT   implicitly closeable  e g  P  LI  TD   or explicitly closeable  e g  TABLE  DIV  SCRIPT   XML  of course  has no concept of this   The tag-soup parsers used by modern browsers evolved out of this legacy  although their parsing model isn t pure SGML anymore  And of course  your carefully-crafted XHTML is being treated as badly-written SGML-inspired tag-soup unless you send it with an XML mime type  This is also why      lt p gt  lt div gt hello lt  div gt  lt  p gt       gets interpreted by the browser as    lt p gt  lt  p gt  lt div gt hello lt  div gt  lt p gt  lt  p gt       which is the recipe for a lovely obscure bug that can throw you into fits as you try to code against the DOM

User · Answer

The self closing script tag won t work  because the script tag can contain inline code  and HTML is not smart enough to turn on or off that feature based on the presence of an attribute      On the other hand  HTML does have an excellent tag for including   references to outside resources  the  lt link gt  tag  and it can be   self-closing  It s already used to include stylesheets  RSS and Atom   feeds  canonical URIs  and all sorts of other goodies  Why not   JavaScript    If you want the script tag to be self enclosed you can t do that as I said  but there is an alternative  though not a smart one  You can use the self closing link tag and link to your JavaScript by giving it a type of text javascript and rel as script  something like below    lt link type  text javascript  rel   script  href   path tp javascript    gt

User · Answer

Internet Explorer 8 and earlier do not support XHTML parsing  Even if you use an XML declaration and or an XHTML doctype  old IE still parse the document as plain HTML  And in plain HTML  the self-closing syntax is not supported  The trailing slash is just ignored  you have to use an explicit closing tag  Even browsers with support for XHTML parsing  such as IE 9 and later  will still parse the document as HTML unless you serve the document with a XML content type  But in that case old IE will not display the document at all

User · Answer

Internet Explorer 8 and earlier do not support XHTML parsing  Even if you use an XML declaration and or an XHTML doctype  old IE still parse the document as plain HTML  And in plain HTML  the self-closing syntax is not supported  The trailing slash is just ignored  you have to use an explicit closing tag  Even browsers with support for XHTML parsing  such as IE 9 and later  will still parse the document as HTML unless you serve the document with a XML content type  But in that case old IE will not display the document at all

User · Answer

To add to what Brad and squadette have said  the self-closing XML syntax  lt script   gt  actually is correct XML  but for it to work in practice  your web server also needs to send your documents as properly formed XML with an XML mimetype like application xhtml xml in the HTTP Content-Type header  and not as text html    However  sending an XML mimetype will cause your pages not to be parsed by IE7  which only likes text html   From w3      In summary   application xhtml xml    SHOULD be used for XHTML Family   documents  and the use of  text html    SHOULD be limited to HTML-compatible   XHTML 1 0 documents   application xml    and  text xml  MAY also be used  but   whenever appropriate     application xhtml xml  SHOULD be used   rather than those generic XML media   types    I puzzled over this a few months ago  and the only workable  compatible with FF3  and IE7  solution was to use the old  lt script gt  lt  script gt  syntax with text html  HTML syntax   HTML mimetype    If your server sends the text html type in its HTTP headers  even with otherwise properly formed XHTML documents  FF3  will use its HTML rendering mode which means that  lt script   gt  will not work  this is a change  Firefox was previously less strict    This will happen regardless of any fiddling with http-equiv meta elements  the XML prolog or doctype inside your document -- Firefox branches once it gets the text html header  that determines whether the HTML or XML parser looks inside the document  and the HTML parser does not understand  lt script   gt

User · Answer

The self closing script tag won t work  because the script tag can contain inline code  and HTML is not smart enough to turn on or off that feature based on the presence of an attribute      On the other hand  HTML does have an excellent tag for including   references to outside resources  the  lt link gt  tag  and it can be   self-closing  It s already used to include stylesheets  RSS and Atom   feeds  canonical URIs  and all sorts of other goodies  Why not   JavaScript    If you want the script tag to be self enclosed you can t do that as I said  but there is an alternative  though not a smart one  You can use the self closing link tag and link to your JavaScript by giving it a type of text javascript and rel as script  something like below    lt link type  text javascript  rel   script  href   path tp javascript    gt

User · Answer

Unlike XML and XHTML  HTML has no knowledge of the self-closing syntax   Browsers that interpret XHTML as HTML don t know that the   character indicates that the tag should be self-closing  instead they interpret it like an empty attribute and the parser still thinks the tag is  open    Just as  lt script defer gt  is treated as  lt script defer  defer  gt    lt script   gt  is treated as  lt script       gt

User · Answer

The people above have already pretty much explained the issue  but one thing that might make things clear is that  though people use  lt br  gt  and such all the time in HTML documents  any   in such a position is basically ignored  and only used when trying to make something both parseable as XML and HTML  Try  lt p  gt foo lt  p gt   for example  and you get a regular paragraph

User · Answer

XHTML 1 specification says     3  Element Minimization and Empty Element Content     Given an empty instance of an element whose content model is not EMPTY  for example  an empty title or paragraph  do not use the minimized form  e g  use  lt p gt   lt  p gt  and not  lt p   gt      XHTML DTD specifies script elements as    lt  -- script statements  which may include CDATA sections -- gt   lt  ELEMENT script   PCDATA  gt

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Others have answered  how  and quoted spec  Here is the real story of  why no  lt script  gt    after many hours digging into bug reports and mailing lists     HTML 4  HTML 4 is based on SGML   SGML has some shorttags  such as  lt BR     lt B gt text lt   gt    lt B text   or  lt OL lt LI gt item lt  LI lt  OL gt   XML takes the first form  redefines the ending as      SGML is flexible   so that it becomes  lt BR  gt    However  HTML did not redfine  so  lt SCRIPT  gt  should mean  lt SCRIPT gt  gt     Yes  the     should be part of content  and the tag is still not closed    Obviously  this is incompatible with XHTML and will break many sites  by the time browsers were mature enough to care about this   so nobody implemented shorttags and the specification advises against them   Effectively  all  working  self-ended tags are tags with prohibited end tag on technically non-conformant parsers and are in fact invalid  It was W3C which came up with this hack to help transitioning to XHTML by making it HTML-compatible   And  lt script gt  s end tag is not prohibited    Self-ending  tag is a hack in HTML 4 and is meaningless     HTML 5  HTML5 has five types of tags and only  void  and  foreign  tags are allowed to be self-closing   Because  lt script gt  is not void  it may have content  and is not foreign  like MathML or SVG    lt script gt  cannot be self-closed  regardless of how you use it   But why  Can t they regard it as foreign  make special case  or something   HTML 5 aims to be backward-compatible with implementations of HTML 4 and XHTML 1  It is not based on SGML or XML  its syntax is mainly concerned with documenting and uniting the implementations   This is why  lt br  gt   lt hr  gt  etc  are valid HTML 5 despite being invalid HTML4    Self-closing  lt script gt  is one of the tags where implementations used to differ  It used to work in Chrome  Safari  and Opera  to my knowledge it never worked in Internet Explorer or Firefox   This was discussed when HTML 5 was being drafted and got rejected because it breaks browser compatibility  Webpages that self-close script tag may not render correctly  if at all  in old browsers  There were other proposals  but they can t solve the compatibility problem either   After the draft was released  WebKit updated the parser to be in conformance   Self-closing  lt script gt  does not happen in HTML 5 because of backward compatibility to HTML 4 and XHTML 1     XHTML 1   XHTML 5  When really served as XHTML   lt script  gt  is really closed  as other answers have stated   Except that the spec says it should have worked when served as HTML      XHTML Documents     may be labeled with the Internet Media Type  text html   RFC2854   as they are compatible with most HTML browsers    So  what happened   People asked Mozilla to let Firefox parse conforming documents as XHTML regardless of the specified content header  known as content sniffing   This would have allowed self-closing scripts  and content sniffing was necessary anyway because web hosters were not mature enough to serve the correct header  IE was good at it   If the first browser war didn t end with IE 6  XHTML may have been on the list  too  But it did end  And IE 6 has a problem with XHTML  In fact IE did not support the correct MIME type at all  forcing everyone to use text html for XHTML because IE held major market share for a whole decade   And also content sniffing can be really bad and people are saying it should be stopped   Finally  it turns out that the W3C didn t mean XHTML to be sniffable  the document is both  HTML and XHTML  and Content-Type rules  One can say they were standing firm on  just follow our spec  and ignoring what was practical  A mistake that continued into later XHTML versions   Anyway  this decision settled the matter for Firefox  It was 7 years before Chrome was born  there were no other significant browser  Thus it was decided   Specifying the doctype alone does not trigger XML parsing because of following specifications

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To add to what Brad and squadette have said  the self-closing XML syntax  lt script   gt  actually is correct XML  but for it to work in practice  your web server also needs to send your documents as properly formed XML with an XML mimetype like application xhtml xml in the HTTP Content-Type header  and not as text html    However  sending an XML mimetype will cause your pages not to be parsed by IE7  which only likes text html   From w3      In summary   application xhtml xml    SHOULD be used for XHTML Family   documents  and the use of  text html    SHOULD be limited to HTML-compatible   XHTML 1 0 documents   application xml    and  text xml  MAY also be used  but   whenever appropriate     application xhtml xml  SHOULD be used   rather than those generic XML media   types    I puzzled over this a few months ago  and the only workable  compatible with FF3  and IE7  solution was to use the old  lt script gt  lt  script gt  syntax with text html  HTML syntax   HTML mimetype    If your server sends the text html type in its HTTP headers  even with otherwise properly formed XHTML documents  FF3  will use its HTML rendering mode which means that  lt script   gt  will not work  this is a change  Firefox was previously less strict    This will happen regardless of any fiddling with http-equiv meta elements  the XML prolog or doctype inside your document -- Firefox branches once it gets the text html header  that determines whether the HTML or XML parser looks inside the document  and the HTML parser does not understand  lt script   gt

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The people above have already pretty much explained the issue  but one thing that might make things clear is that  though people use  lt br  gt  and such all the time in HTML documents  any   in such a position is basically ignored  and only used when trying to make something both parseable as XML and HTML  Try  lt p  gt foo lt  p gt   for example  and you get a regular paragraph

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To add to what Brad and squadette have said  the self-closing XML syntax  lt script   gt  actually is correct XML  but for it to work in practice  your web server also needs to send your documents as properly formed XML with an XML mimetype like application xhtml xml in the HTTP Content-Type header  and not as text html    However  sending an XML mimetype will cause your pages not to be parsed by IE7  which only likes text html   From w3      In summary   application xhtml xml    SHOULD be used for XHTML Family   documents  and the use of  text html    SHOULD be limited to HTML-compatible   XHTML 1 0 documents   application xml    and  text xml  MAY also be used  but   whenever appropriate     application xhtml xml  SHOULD be used   rather than those generic XML media   types    I puzzled over this a few months ago  and the only workable  compatible with FF3  and IE7  solution was to use the old  lt script gt  lt  script gt  syntax with text html  HTML syntax   HTML mimetype    If your server sends the text html type in its HTTP headers  even with otherwise properly formed XHTML documents  FF3  will use its HTML rendering mode which means that  lt script   gt  will not work  this is a change  Firefox was previously less strict    This will happen regardless of any fiddling with http-equiv meta elements  the XML prolog or doctype inside your document -- Firefox branches once it gets the text html header  that determines whether the HTML or XML parser looks inside the document  and the HTML parser does not understand  lt script   gt

User · Answer

The people above have already pretty much explained the issue  but one thing that might make things clear is that  though people use  lt br  gt  and such all the time in HTML documents  any   in such a position is basically ignored  and only used when trying to make something both parseable as XML and HTML  Try  lt p  gt foo lt  p gt   for example  and you get a regular paragraph

User · Answer

XHTML 1 specification says     3  Element Minimization and Empty Element Content     Given an empty instance of an element whose content model is not EMPTY  for example  an empty title or paragraph  do not use the minimized form  e g  use  lt p gt   lt  p gt  and not  lt p   gt      XHTML DTD specifies script elements as    lt  -- script statements  which may include CDATA sections -- gt   lt  ELEMENT script   PCDATA  gt

[javascript] Why don't self-closing script elements work?

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