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HTML TIDY - Notes on Pending Work

Dave Raggett

This is a page where I am keeping the suggestions for improvements or bug fixes. My current work load means that I don't get much time to work on HTML Tidy, so I am interested in offers of help!

Public Email List for Tidy: <>

I have set up an archived mailing list devoted to Tidy. To subscribe send an email to with the word subscribe in the subject line (include the word unsubscribe if you want to unsubscribe). The archive for this list is accessible online. Please use this list to report errors or enhancement requests.

Things awaiting further attention

  • Support for BIG5 and ShiftJIS (Rick Jelliffe)
  • Stronger checking on which attributes appear on what elements
  • Sorting attributes in a canonical order
  • Version checking for HTML 4.01 vs 4.0 (Tidy currently will set the document type to 4.01 in preference to 4.0)
  • Noticing that the document isn't really XHTML if it isn't wellformed, i.e. it lacks end tags and quotes on attribute values
  • Converting <font face="Symbol">a</font> etc. to the corresponding Unicode characters, when cleaning HTML.
  • link checking - this would involve some platform dependent code as the network interface varies significantly from one platform to the next.
  • When exporting Word2000 to Web page, there is a need for smarter rules of thumb for working out whether the paragraph is a bulletted or numbered list item, and determining the level of nesting. Perhaps the style attribute holds the key? This tends to include substrings like: "mso-list:l0 level1 lfo2;" and "mso-list:l1 level1 lfo1;". Unfortunately, these aren't always present, and I have yet to figure out a foolproof heuristic.

I need to set up an index of precisely what attributes are supported on each element. Right now, some elements check their own attributes, whilst others are checked via default checks defined for each attribute independently of the element. Until this is done, you sometimes find that validation services discovering errors unnoticed by Tidy itself.

Jelks Cabaniss asks: Could Tidy be made to automatically "clean" (FONTs to CSS) if the Strict DOCTYPE is requested? An HTML or XHTML Strict document can't have FONT tags according to the DTDs. Jelks has a bunch of other good ideas such as converting the bgcolor attribute over to CSS.

Adding an option to select slide transition effects. I would also like to provide an optional feature for sorting attribute values.

I am having problems with form elements as direct children of tr or table. It is dangerous to create an implicit table cell, and what is needed is a way to move the form element into the next cell. If this can't be done an error needs to be raised since Tidy will be stuck. On a separate note, Tidy is still breaking lines between <img> and </a> which in Netscape shows as an underlined space. It's fine in IE.

Benjamin Holzman <> writes: I'm wrapping tidy (release-date 2000.01.13) in some perl objects (using SWIG), and CharEncoding being a global is a bit of a pain. I was wondering what your thoughts would be on how to fix that. The character encoding is already a property of struct Out; is there any reason why making it part of struct StreamIn as well, and perhaps setting that property in OpenInput, based on the existing CharEncoding variable, wouldn't allow us to move CharEncoding to be local to main?

Oh, in case you're curious about the API, here's a short script using my wrappers to be an html to xhtml filter:


      require tidy;

      my $tidy     = Tidy->new(*STDIN);
      my $document = $tidy->parse;

Rick Parsons would like there to be a new wrap-attributes option that can be used to suppress line wrapping within attributes. There is already a similar option for JavaScript literals.

Vijay Patil would like tidy -h to display options sorted alphabetically.

Julian Reschke would like there to be an option to add the

Armando Asantos would like to use Tidy to produce a list of URLs for images or hypertext links according to a config option. This would be straightforward, but is a lower priority than bug fixes etc.

Omri Traub would like an option to wrap the contents of style and script elements in CDATA marked sections when converting to XHTML. He is also interested in direct support for 16 bit character file I/O.

Bertilo Wennergren notes:

If I configure Tidy to "upgrade to style sheets", it does so for a few things in my main document, but the code thus created get error reports if I feed it back to Tidy. It turns out that Tidy creates extra "class" attributes on tags that already have "class" attributes set. This happens with this page: <>.

Randi Waki notes:

If a quoted URL attribute value (e.g., href in <a> elements) contains a line break, 13-Jan-2000 Tidy changes the line break to a space while IE and Netscape discard the line break. This can result in a broken link in the tidied document.

I believe the following change fixes the problem. In lexer.c, insert the following lines before line 2502:

                            /* discard line breaks in quoted URLs */
                            if (c == '\n' && IsUrl(name))

/* existing line 2502 */    c = ' ';

Stephen Reynolds would like Tidy to keep track of whether a comment started on a new line and preserve this in the output.

Terry Teague says:

Sorry, I should have been more clear. Part of the problem is the current HelpText() function in localize.c doesn't actually reflect current reality.

You need to at least add the following line to HelpText() :

    tidy_out(out, "  -version or -v  show version\n");

And I suppose it should mention the use of the new "--<config options>" type syntax.

Regards, Terry

John Russel notes:

 what i wonder is
1] does the specification indicate these are WRONG
2] if so why do they pass thru tidy ....
is url syntax such a can of worms that it is left to user
   to check .......

CASE 1: misuse of slash for folders
site had  background="pics\fancy.jpg"
  instead of   "pics/fancy.jpg"

CASE 2: spaces in filename
site had href="coin album.html"
instead of "coin%20album.html"

Andre Stechert would like a way to prevent Tidy from "cleaning" newly declared elements which don't have any content but do have end tags, see his mail of 17th January 2000

Todd Clark would like to use Tidy with Microsoft's WebClass tags. Unfortunately these include unusual characters in the tag names such as @ which Tidy objects to, for instance:


Perhaps it makes sense to offer an option to make Tidy less picky about what characters it accepts in tag names. Or perhaps "WebClass: yes".

Jelks Cabaniss suggests an option to control dropping of empty elements, e.g. according to what attributes they have.

Paavo Hartikainen writes:

Tidy always expands '&' to '&' even if I have 'quote-ampersand: no' defined in configuration file. This is not a good thing to do for URLs that have '&' characters in them. OS is Debian GNU/Linux 2.1 SPARC. Same thing happens on Alpha. Other architectures I have not tried.

My configuration looks like this:

char-encoding: latin1
error-file: ./errors
indent-spaces: 2
logical-emphasis: yes
output-xhtml: yes
quiet: no
quote-ampersand: no
show-warnings: yes
tidy-mark: yes
wrap: 78
wrap-attributes: no
write-back: yes
keep-time: yes

Paul White reports that Tidy isn't recognizing HTML 3.2 when the doctype is "-//W3C//DTD HTML 3.2 Final//EN" (as per the REC), and similarly for HTML 4.01. This would appear to call for a change to the table of names in lexer.c.

Stuart Hungerford would like Tidy to detect and fix duplicate attributes e.g. multiple class attributes. Celeste Suliin Burris would like Tidy to replace spaces in URLs by %20 as some versions of Netscape "croak big time" on this. Denis Kokarev also wants Tidy to remove duplicate attributes when the values are the same. This apparently stops XSLT from working. Brian Schweitzer notes that Tidy adds a 2nd class attribute rather than merging the classes into a space separated list.

Bertilo Wennergren writes: Tidy seems not to recognize frame elements with a closing "/". It actually removes them. Try his example. Tidy can produce XHTML Frameset docs, but when fed them back

again it cries foul.

Jose Manuel Cerqueira Esteves notes:

I've used `tidy' to convert a few HTML 4.0 files to XHTML 1.0 and noticed
a problem when dealing with constructs like

 <small><small>some text</small></small>

First, `tidy' acts as if the second "<small>" was meant as a closing tag:

 Warning: "<small> is probably intended as </small>"

Then it trims the resulting empty <small></small>:

 Warning: trimming empty <small>

And finally both remaining closing tags ("</small>"), now spurious,
are removed:

 Warning: discarding unexpected </small>
 Warning: discarding unexpected </small>

It would be convenient to have at least some `tidy' option to prevent this
from happening (or perhaps some different heuristics?).

Robbert Hans Baron would like to see Tidy warning about duplicate attributes and fixing these when the values are identical.

Jutta Wrage notes that: When parsing HTML 3.2 Pages, tidy doesn't accept textareas in forms correctly. The HTML Reference specification (HTML 3.2 Final) allows: name, rows and cols, but upon seeing these Tidy thinks the document is 4.0.

Matthew Brealey notes that a heading start tag is coerced to an end heading tag when the end tag is missing. This is deliberate, but perhaps not the best heuristic.

HIYAMA Masayuki notes that Tidy should set the encoding encoding="iso-2022-jp"?><.

Mark Modrall has extended Tidy to support selectively stripping out listed tags and attributes, see his email of March 14th.

Yong Taek Bae notes that with the omit end tags option Tidy omits the body tag even if it has attributes. This is an error.

Tapio Markula reports that Tidy is incorrectly replacing accented characters in script elements by entities. The script element (in HTML but not XHTML) is CDATA and as such entities won't be expanded. This bug needs to be fixed along with the support for CDATA sections.

Terrill Bennett reports tidy crashing when producing slides, and when the -i option has been set. He later added the crash occurs when the page doesn't include an h1 element. See Terrill-Bennett-11mar00.txt.

Stephen Lewis notes that if an <hr> element is present in the head before the title element, then Tidy gets confused and adds in a spurious extra empty title element. This would be avoided if Tidy could move the hr into the body before the body element is encountered. This raises a number of problems for instance working out when to copy in attributes from an explicit body element.

Carl Osterly would like Tidy to avoid breaking lines before or after the = sign in attribute values when this is practical. Perhaps a simple rule of thumb could be used to decide this?

Rick H Wesson notes that Tidy crashes on CDATA marked sections when parsing XML.

Luigi Federici would like an option to set the DTD URI for XML or XHTML.

Mat Sander notes: If I have php code the indentation behaves strange. Repeated tidying php content and end tag indented one level extra for each time. The result ends up something like this:


I have the fillowing config file for Tidy:
tidy-mark: no
markup: yes
wrap: 0
indent: auto
output-xhtml: yes
doctype: loose
char-encoding: latin1
quote-marks: yes
word-2000: yes
clean: yes
logical-emphasis: yes
drop-empty-paras: yes
enclose-text: yes
fix-bad-comments: yes
alt-text: .
write-back: bool
keep-time: yes
show-warnings: no
quiet: yes
split: no

Best Regards,
Mats-Olof Sander

Don Hasson notes that if you make a mistake and leave off the ending "/" in the <title> tag, tidy will generate an extra set of <title>s.


<head><title>No end here<title></head>

produces this:

<title>No end here</title>

Jeff Wilkinson would like the HTML Tidy page to include internal anchors so that he can link directly to the appropriate sections.

Peter Vince would like to be able to clean presentation attributes on the body element, as well as translating b and i to span.

Dave Bryan and Mathew Brealey would like there to be a way to suppress the default handling of inline elements in favor of simply inserting the appropriate end tag when encountering an element that isn't allowed in an inline context. The default behavior replicates the rendering on existing browsers but can cause problems for hand editors.

Dave Bryan notes that tidy isn't updating the column position when parsing attributes.

Can Tidy track when a line break occurs after a PI or comment and reproduce this in the output? This idea occurred to me after reading a comment from Brad Stowers.

One interesting suggestion is to make some of Tidy's rules of thumb sensitive to the program that generated the markup as indicated by the meta element. This would allow for greater robustness in how the rules operate.

Dave Bryan would like the quiet mode to be tweaked to suppress the general info at the end of the report. see Dave-Bryan-24mar00.txt.

Erik Rossen would like an option to suppress line wrap within tags, so that the tag is always on the same line regardless of the number and length of the attributes.

Dan Satria suggest that the clean mechanism check to see if there are any existing matching style rules before adding new ones.

Zoltan Hawryluk suggests mapping the Netscape layer tag into the equivalent CSS positioning syntax.

Jim Walker says Tidy doesn't correctly report errors such as </</head>.

Tidy's slide feature: see Johannes-Poutre-12jul00.txt

Carole Mah suggests Tidy should recover from multiple class attributes on the same element.

Other ideas

  • Recursion through subdirectories, so you can fix up your entire web site at one go. This assumes I can find a way that is portable across a wide range of platforms!
  • Support for W3C's Document Object Model (DOM) level one.
  • Full validation of all attribute values.
  • Mapping Unicode bidi control characters to HTML tags.
  • Full support for parsing XML (still somewhat limited).
  • How to say which XML elements should be printed "inline".
  • Acting on the XML encoding attribute, e.g.
  • Improved mapping from HTML presentation attributes/elements to CSS.
  • Improved support for JSP (Java Server pages)
  • Ugly print option which removes all optional whitespace