'Colspan all columns

How can I specify a td tag should span all columns (when the exact amount of columns in the table will be variable/difficult to determine when the HTML is being rendered)? w3schools mentions you can use colspan="0", but it doesn't say exactly what browsers support that value (IE 6 is in our list to support).

It appears that setting colspan to a value greater than the theoretical amount of columns you may have will work, but it will not work if you have table-layout set to fixed. Are there any disadvantages to using an automatic layout with a large number for colspan? Is there a more correct way of doing this?

Solution 1:^[1]

Just use this:

colspan="100%"

It works on Firefox 3.6, IE 7 and Opera 11! (and I guess on others, I couldn't try)

Warning: as mentioned in the comments below this is actually the same as colspan="100". Hence, this solution will break for tables with css table-layout: fixed, or more than 100 columns.

Solution 2:^[2]

If you want to make a 'title' cell that spans all columns, as header for your table, you may want to use the caption tag (http://www.w3schools.com/tags/tag_caption.asp / https://developer.mozilla.org/en-US/docs/Web/HTML/Element/caption) This element is meant for this purpose. It behaves like a div, but doesn't span the entire width of the parent of the table (like a div would do in the same position (don't try this at home!)), instead, it spans the width of the table. There are some cross-browser issues with borders and such (was acceptable for me). Anyways, you can make it look as a cell that spans all columns. Within, you can make rows by adding div-elements. I'm not sure if you can insert it in between tr-elements, but that would be a hack I guess (so not recommended). Another option would be messing around with floating divs, but that is yuck!

<table>
    <caption style="gimme some style!"><!-- Title of table --></caption>
    <thead><!-- ... --></thead>
    <tbody><!-- ... --></tbody>
</table>

Don't

<div>
    <div style="float: left;/* extra styling /*"><!-- Title of table --></div>
    <table>
        <thead><!-- ... --></thead>
        <tbody><!-- ... --></tbody>
    </table>
    <div style="clear: both"></div>
</div>

Solution 3:^[3]

As a partial answer, here's a few points about colspan="0", which was mentioned in the question.

tl;dr version:

colspan="0" doesn't work in any browser whatsoever. W3Schools is wrong (as usual). HTML 4 said that colspan="0" should cause a column to span the whole table, but nobody implemented this and it was removed from the spec after HTML 4.

Some more detail and evidence:

All major browsers treat it as equivalent to colspan="1".

Here's a demo showing this; try it on any browser you like.

td {
  border: 1px solid black;
}

<table>
  <tr>
    <td>ay</td>
    <td>bee</td>
    <td>see</td>
  </tr>
  <tr>
    <td colspan="0">colspan="0"</td>
  </tr>
  <tr>
    <td colspan="1">colspan="1"</td>
  </tr>
  <tr>
    <td colspan="3">colspan="3"</td>
  </tr>
  <tr>
    <td colspan="1000">colspan="1000"</td>
  </tr>
</table>

The HTML 4 spec (now old and outdated, but current back when this question was asked) did indeed say that colspan="0" should be treated as spanning all columns:

The value zero ("0") means that the cell spans all columns from the current column to the last column of the column group (COLGROUP) in which the cell is defined.

However, most browsers never implemented this.
HTML 5.0 (made a candidate recommendation back in 2012), the WhatWG HTML living standard (the dominant standard today), and the latest W3 HTML 5 spec all do not contain the wording quoted from HTML 4 above, and unanimously agree that a colspan of 0 is not allowed, with this wording which appears in all three specs:

The td and th elements may have a colspan content attribute specified, whose value must be a valid non-negative integer greater than zero ...

Sources:
The following claims from the W3Schools page linked to in the question are - at least nowadays - completely false:

Only Firefox supports colspan="0", which has a special meaning ... [It] tells the browser to span the cell to the last column of the column group (colgroup)

and

Differences Between HTML 4.01 and HTML5

NONE.

If you're not already aware that W3Schools is generally held in contempt by web developers for its frequent inaccuracies, consider this a lesson in why.

Solution 4:^[4]

For IE 6, you'll want to equal colspan to the number of columns in your table. If you have 5 columns, then you'll want: colspan="5".

The reason is that IE handles colspans differently, it uses the HTML 3.2 specification:

IE implements the HTML 3.2 definition, it sets colspan=0 as colspan=1.

The bug is well documented.

Solution 5:^[5]

If you're using jQuery (or don't mind adding it), this will get the job done better than any of these hacks.

function getMaxColCount($table) {
    var maxCol = 0;

    $table.find('tr').each(function(i,o) {
        var colCount = 0;
        $(o).find('td:not(.maxcols),th:not(.maxcols)').each(function(i,oo) {
            var cc = Number($(oo).attr('colspan'));
            if (cc) {
                colCount += cc;
            } else {
                colCount += 1;
            }
        });
        if(colCount > maxCol) { 
            maxCol = colCount; 
        }
    });

    return maxCol;
}

To ease the implementation, I decorate any td/th I need adjusted with a class such as "maxCol" then I can do the following:

$('td.maxcols, th.maxcols').each(function(i,o) {
    $t = $($(o).parents('table')[0]); $(o).attr('colspan',  getMaxColCount($t));
});

If you find an implementation this won't work for, don't slam the answer, explain in comments and I'll update if it can be covered.

Solution 6:^[6]

Another working but ugly solution : colspan="100", where 100 is a value larger than total columns you need to colspan.

According to the W3C, the colspan="0" option is valid only with COLGROUP tag.

Solution 7:^[7]

Below is a concise es6 solution (similar to Rainbabba's answer but without the jQuery).

Array.from(document.querySelectorAll('[data-colspan-max]')).forEach(td => {
    let table = td;
    while (table && table.nodeName !== 'TABLE') table = table.parentNode;
    td.colSpan = Array.from(table.querySelector('tr').children).reduce((acc, child) => acc + child.colSpan, 0);
});

html {
  font-family: Verdana;
}
tr > * {
  padding: 1rem;
  box-shadow: 0 0 8px gray inset;
}

<table>
<thead>
  <tr>
    <th>Header 1</th>
    <th>Header 2</th>
    <th>Header 3</th>
    <th>Header 4</th>
    <th>Header 5</th>
    <th>Header 6</th>
  </tr>
</thead>
<tbod><tr>
  <td data-colspan-max>td will be set to full width</td>
</tr></tbod>
</table>

Solution 8:^[8]

Simply set `colspan` to the number of columns in the table.

All other "shortcuts" have pitfalls.

The best thing to do is set the colspan to the correct number to begin with. If your table has 5 columns, set it to colspan="5" That is the only way that will work in all scenarios. No, it's not an outdated solution or only recommended for IE6 or anything -- that's literally the best way to handle this.

I wouldn't recommend using Javascript to solve this unless the number of columns changes during runtime.

If the number of columns is variable, then you'll need to calculate the number of columns so that you can populate the colspan. If you have a variable number of columns, whatever is generating the table should be able to be adapted to also calculate the number of columns the table has.

As other answers have mentioned, if your table is not set to table-layout: fixed, you can also just set colspan to a really large number. But I find this solution messy, and it can be a headache if you come back later and decide it should be a fixed table layout. Better just to do it correctly the first time.

Solution 9:^[9]

A CSS solution would be ideal, but I was unable to find one, so here is a JavaScript solution: for a tr element with a given class, maximize it by selecting a full row, counting its td elements and their colSpan attributes, and just setting the widened row with el.colSpan = newcolspan;. Like so...

var headertablerows = document.getElementsByClassName('max-col-span');

[].forEach.call(headertablerows, function (headertablerow) {
    var colspan = 0;
    [].forEach.call(headertablerow.nextElementSibling.children, function (child) {
        colspan += child.colSpan ? parseInt(child.colSpan, 10) : 1;
    });
    
    headertablerow.children[0].colSpan = colspan;
});

html {
  font-family: Verdana;
}
tr > * {
  padding: 1rem;
  box-shadow: 0 0 8px gray inset;
}

  <table>
    <tr class="max-col-span">
      <td>1 - max width
      </td>
    </tr>
    <tr>
      <td>2 - no colspan
      </td>
      <td colspan="2">3 - colspan is 2
      </td>
    </tr>
  </table>

You may need to adjust this if you're using table headers, but this should give a proof-of-concept approach that uses 100% pure JavaScript.

Solution 10:^[10]

Just want to add my experience and answer to this.
Note: It only works when you have a pre-defined table and a tr with ths, but are loading in your rows (for example via AJAX) dynamically.

In this case you can count the number of th's there are in your first header row, and use that to span the whole column.

This can be needed when you want to relay a message when no results have been found.

Something like this in jQuery, where table is your input table:

var trs = $(table).find("tr");
var numberColumns = 999;
if (trs.length === 1) {
    //Assume having one row means that there is a header
    var headerColumns = $(trs).find("th").length;
    if (headerColumns > 0) {
        numberColumns = headerColumns;
    }
}

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	HoldOffHunger
Solution 2	natevw
Solution 3
Solution 4	George Stocker
Solution 5	frankenapps
Solution 6	rink.attendant.6
Solution 7	Sjeiti
Solution 8	Skeets
Solution 9	HoldOffHunger
Solution 10	skiwi

'Colspan all columns

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

tl;dr version:

Some more detail and evidence:

Differences Between HTML 4.01 and HTML5

Solution 4:[4]

Solution 5:[5]

Solution 6:[6]

Solution 7:[7]

Solution 8:[8]

Simply set colspan to the number of columns in the table.