CSS Specificity: Things You Should Know

Advertisement

Apart from Floats1, the CSS Specificity is one of the most difficult concepts to grasp in Cascading Stylesheets. The different weight of selectors is usually the reason why your CSS-rules don’t apply to some elements, although you think they should have. In order to minimize the time for bug hunting you need to understand, how browsers interpret your code. And to understand that, you need to have a firm understanding on how specificity works. In most cases such problems are caused by the simple fact that somewhere among your CSS-rules you’ve defined a more specific selector.

CSS Specificity isn’t simple. However, there are methods to explain it in a simple and intuitive way. And that’s what this article is all about. You’ll understand the concept if you love Star Wars2. Really.

Let’s take a look at some important issues related to CSS Specificity as well as examples, rules, principles, common solutions and resources.

  • You can find the most important things you should know about CSS specificity in a brief overview at the beginning of the article.

CSS Specificity: An Overview

  1. Specificity determines, which CSS rule is applied by the browsers.
  2. Specificity is usually the reason why your CSS-rules don’t apply to some elements, although you think they should.
  3. Every selector has its place in the specificity hierarchy.
  4. If two selectors apply to the same element, the one with higher specificity wins.
  5. There are four distinct categories which define the specificity level of a given selector: inline styles, IDs, classes+attributes and elements.
  6. You can understand specificity if you love Star Wars: CSS Specificity Wars3.
  7. You can understand specificity if you love poker: CSS Specificity for Poker Players24184
  8. When selectors have an equal specificity value, the latest rule is the one that counts.
  9. When selectors have an unequal specificity value, the more specific rule is the one that counts.
  10. Rules with more specific selectors have a greater specificity.
  11. The last rule defined overrides any previous, conflicting rules.
  12. The embedded style sheet has a greater specificity than other rules.
  13. ID selectors have a higher specificity than attribute selectors.
  14. You should always try to use IDs to increase the specificity.
  15. A class selector beats any number of element selectors.
  16. The universal selector and inherited selectors have a specificity of 0, 0, 0, 0.
  17. You can calculate CSS specificity with CSS Specificity Calculator.

What is Specificity?

  • Specificity determines, which CSS rule is applied by browsers. “Specificity is a type of weighting that has a bearing on how your cascading style sheet (CSS) rules are displayed.” [Understanding Specificity75]
  • Selector specificity is a process used to determine which rules take precedence in CSS when several rules could be applied to the same element in markup. [Selector Specificity226]
  • Every selector has its specificity. “All rules in your CSS carry a specificity rating regardless of selector type, although the weighting that is given to each selector type varies and will ultimately affect the styling of your web documents.” [Understanding Specificity75]
  • If two selectors apply to the same element, the one with higher specificity wins.

Specificity hierarchy

  • Every selector has its place in the specificity hierarchy. There are four distinct categories which define the specificity level of a given selector:

    1. Inline styles (Presence of style in document).
    An inline style lives within your XHTML document. It is attached directly to the element to be styled. E.g. <h1 style="color: #fff;">

    2. IDs (# of ID selectors)
    ID is an identifier for your page elements, such as #div.

    3. Classes, attributes and pseudo-classes (# of class selectors).
    This group includes .classes, [attributes] and pseudo-classes such as :hover, :focus etc.

    4. Elements and pseudo-elements (# of Element (type) selectors).
    Including for instance :before and :after.

If you don’t know what exactly each of these terms stands for, you can take a look at the brief overview of them; in the last section of this article.

How to measure specificity?

  • Memorize how to measure specificity. “Start at 0, add 1000 for style attribute, add 100 for each ID, add 10 for each attribute, class or pseudo-class, add 1 for each element name or pseudo-element. So in
    body #content .data img:hover

    the specificity value would be 122 (0,1,2,2 or 0122): 100 for #content, 10 for .data, 10 for :hover, 1 for body and 1 for img.” [CSS Specificity8]

  • Alternative way: “Count the number of ID attributes in the selector (= a). Count the number of other attributes and pseudo-classes in the selector (= b). Count the number of element names and pseudo-elements in the selector (= c). Concatenating the three numbers a-b-c gives the specificity. [CSS Selector Specificity9]
  • CSS Specificity Wars – Cheat Sheet10
    To help me understand calculating specificity better I made a chart based on the following specificity (or Sith power) values. Each character (selector) is given its own Sith power (specificity value) depending on how powerful they are in the ways of the Dark Side. A storm trooper is less powerful than Vader who is in turn less powerful than the Emperor.

CSS Specificity Wars11

    Specificity Examples: Test Yourself

    It’s easier to calculate the specificity using the first method. Let’s find out, how it actually is done.

    1 * { } 0
    2 li { } 1 (one element)
    3 li:first-line { } 2 (one element, one pseudo-element)
    4 ul li { } 2 (two elements)
    5 ul ol+li { } 3 (three elements)
    6 h1 + *[rel=up] { } 11 (one attribute, one element)
    7 ul ol li.red { } 13 (one class, three elements)
    8 li.red.level { } 21 (two classes, one element)
    9 style=”” 1000 (one inline styling)
    10 p { } 1 (one HTML selector)
    11 div p { } 2 (two HTML selectors)
    12 .sith 10 (one class selector)
    13 div p.sith { } 12 (two HTML selectors and a class selector)
    14 #sith 100 (one id selector)
    15 body #darkside .sith p { } 112 (HTML selector, id selector, class selector, HTML selector; 1+100+10+1)

    Specificity: Basic Principles

    • Equal specificity: the latest rule is the one that counts. “If you have written the same rule into your external style sheet twice, than the lower rule in your style sheet is closer to the element to be styled, it is deemed to be more specific and therefore will be applied.
      When selectors have an equal specificity value, such as

      #content h1 {
      padding: 5px;
      }
      
      #content h1 {
      padding: 10px;
      }

      where both rules have the specificity 0, 1, 0, 1, the latter rule is always applied.

    • Unequal specificity: the more specific rule is the one that counts. “A selector can contain one or more reference points, the greater the specificity rating of these reference points the more specific your rule is.” Browsers select the most specific rules to display. [Understanding Specificity1612]

    Specificity Rules

    • Rules with more specific selectors have a greater specificity. The more specific the references are in your selector, the greater the specificity for the rule. [Understanding Specificity13]
    • ID selectors have a higher specificity than attribute selectors. For example, in HTML, the selector #p123 is more specific than [id=p123] in terms of the cascade. Example: in
      A:
      a#a-02 { background-image : url(n.gif); }
      
      and
      
      B:
      a[id="a-02"] { background-image : url(n.png); }

      the first rule (A) is more specific than the second one (B). [W3C CSS 2.1 Specification14]

    • Contextual selectors are more specific than a single element selector. It also holds for other selectors involving more than one HTML element selector. [Cascade Inheritance15]
    • The embedded style sheet is closer to the element to be styled. So in the following situation

      CSS:

      #content h1 {
      padding: 5px;
      }

      (X)HTML:

      <style type="text/css">
      #content h1 {
      padding: 10px;
      }
      </style>

      the latter rule will be applied. [Understanding Specificity1612]

    • The last rule defined overrides any previous, conflicting rules. For example, given these two rules
      p { color: red; background: yellow }
      p { color: green }

      paragraphs would appear in green text. They would also have a yellow background however, because the first rule is not completely negated. [BrainJar.com17]

    • A class selector beats any number of element selectors. .introduction beats html body div div h2 p. [CSS Specificity for Poker Players24184]
    • The universal selector has a specificity of 0, 0, 0, 0. *, body * and similar selectors have a zero specificity. Inherited values also have a specificity of 0, 0, 0, 0. [CSS Specificity Clarified19]

    Specificity Example

    • Consider three code fragments:
      A: h1
      B: #content h1
      C: <div id="content">
      <h1 style="color: #fff">Headline</h1>
      </div>

      The specificity of A is 0,0,0,1 (one element), the specificity of B is 0,1,0,1 (one ID reference point and one element), the specificity value of C is 1,0,0,0, since it is an inline styling.

      Since

      0001 = 1 < 0101 = 101 < 1000,

      the third rule has a greater level of specificity, and therefore will be applied. If the third rule didn’t exist, the second rule would have been applied.

    Specificity in Practice

    • Use LVHA for link styling.
      “To ensure that you see your various link styles, you’re best off putting your styles in the order “link-visited-hover-active”, or “LVHA” for short.” [Link Specificity20]
    • Never use !important.
      “If you’re having specificity issues, there’s some quick ways to solve it. First, avoid !important.” “The !important declaration overrides normal declarations, but is unstructured and rarely required in an author’s style sheet.” [Understanding Specificity2321, Selector Specificity226]
    • Use id to make a rule more specific.
      Replacing a.highlight with ul#blogroll a.highlight changes the specificity from 0, 0, 1, 1 to 0, 1, 1, 2.
    • Minimize the number of selectors.
      “Use the least number of selectors required to style an element.” [Understanding Specificity2321]

    CSS Specificity Tools & Resources

    • CSS Specificity for Poker Players24184
      If you’re not from the programming world and CSS seems a bit confusing, perhaps this analogy may help clear some concepts up. Think of CSS rules as poker hands. The best hand determines an element’s style.
    • CSS specificity calculator
      Calculates the specificity of a given selector.
    • Understanding Specificity Tutorial25
      In this tutorial you will look at specificity. Specificity is a type of weighting that has a bearing on how your cascading style sheet (CSS) rules are displayed. All rules in your style sheet carry a specificity rating regardless of selector type, although the weighting that is given to each selector type varies and will ultimately affect the styling of your web documents.
    • Cascade Inheritance: Specificity26
      At this point it might be timely to have a quick discussion of specificity. Both inside a single style sheet, and in a cascade of style sheets, it should be clear that more than one rule can apply to the same element. What happens when two properties in separate rules which both apply to an element contradict one another?
    • CSS 2.1 Selectors Explained27
      An extensive overview of CSS 2.1 selectors. Learning how to use the full range of CSS selectors available in CSS 2.1 properly can actually help you keep your HTML a lot cleaner. It will let you minimise unnecessary use of the class attribute and the need for adding extraneous div and span elements to the markup.
    • CSS Specificity Bugs in IE28
      A brief overview of specificity bugs implemented in Microsoft Internet Explorer/Win.
    • CSS Structure and Rules29
      Basic Syntax, Pseudo-classes and Pseudo-elements, Cascading Order.
    • Specificity30
      It may not seem like something that important, and in most cases you won’t come across any conflicts at all, but the larger and more complex your CSS files become, or the more CSS files you start to juggle with, the greater likelihood there is of conflicts turning up.

    What is what?

    • A selector is the element that is linked to a particular style. E.g. p in
      p { padding: 10px; }
    • A class selector is a selector that uses a defined class (multiple per page). E.g. p.section in
      p.section { padding: 10px; }
    • An ID selector is a selector that uses an individually assigned identifier (one per page). E.g. p#section in
      CSS: #section { padding: 10px; }
      (X)HTML: <p id="section">Text</>
    • A contextual selector is a selector that defines a precise cascading order for the rule. E.g. p span in
      p span { font-style: italic; }

      defines that all span-elements within a p-element should be styled in italics.

    • An attribute selector matches elements which have a specific attribute or its value. E.g. p span in
      p[title] { font-weight: bold; }

      matches all p-elements which have a title attribute.

    • Pseudo-classes are special classes that are used to define the behavior of HTML elements. They are used to add special effects to some selectors, which are applied automatically in certain states. E.g. :visited in
      a:visited { text-decoration: underline; }
    • Pseudo-elements provide designers a way to assign style to content that does not exist in the source document. Pseudo-element is a specific, unique part of an element that can be used to generate content “on the fly”, automatic numbering and lists. E.g. :first-line or :after in
      p:first-line { font-variant: small-caps; }
      a:link:after { content: " (" attr(href) ")"; }

    Footnotes

    1. 1 http://www.smashingmagazine.com/2007/05/01/css-float-theory-things-you-should-know/
    2. 2 http://en.wikipedia.org/wiki/Star_Wars
    3. 3 http://www.stuffandnonsense.co.uk/archives/css_specificity_wars.html
    4. 4 http://iamacamera.org/default.aspx?id=95
    5. 5 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity.html
    6. 6 http://juicystudio.com/article/selector-specificity.php
    7. 7 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity.html
    8. 8 http://forums.invisionpower.com/lofiversion/index.php/t176404.html
    9. 9 http://juicystudio.com/article/selector-specificity.php
    10. 10 http://www.stuffandnonsense.co.uk/archives/css_specificity_wars.html
    11. 11 http://www.stuffandnonsense.co.uk/archives/css_specificity_wars.html
    12. 12 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity_02.html
    13. 13 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity_03.html
    14. 14 http://www.w3.org/TR/CSS21/selector.html
    15. 15 http://www.westciv.com/style_master/academy/css_tutorial/advanced/cascade_inheritance.html#specificity
    16. 16 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity_02.html
    17. 17 http://www.brainjar.com/css/using/default4.asp
    18. 18 http://iamacamera.org/default.aspx?id=95
    19. 19 http://molly.com/2005/10/06/css2-and-css21-specificity-clarified/
    20. 20 http://meyerweb.com/eric/css/link-specificity.html
    21. 21 http://www.snook.ca/archives/html_and_css/understanding_c/
    22. 22 http://juicystudio.com/article/selector-specificity.php
    23. 23 http://www.snook.ca/archives/html_and_css/understanding_c/
    24. 24 http://iamacamera.org/default.aspx?id=95
    25. 25 http://www.adobe.com/devnet/dreamweaver/articles/css_specificity.html
    26. 26 http://www.westciv.com/style_master/academy/css_tutorial/advanced/cascade_inheritance.html#specificity
    27. 27 http://www.456bereastreet.com/archive/200509/css_21_selectors_part_1/
    28. 28 http://www.brunildo.org/test/IEASpec.html
    29. 29 http://www.htmlhelp.com/reference/css/structure.html
    30. 30 http://www.htmldog.com/guides/cssadvanced/specificity/

    ↑ Back to top Tweet itShare on Facebook

    Vitaly Friedman loves beautiful content and doesn’t like to give in easily. Vitaly is writer, speaker, author and editor-in-chief of Smashing Magazine. He runs responsive Web design workshops, online workshops and loves solving complex performance problems in large companies. Get in touch.

    Related Articles

    Advertising
    1. 1

      This is a great article. It’s a complicated subject, and one where clear, understandable information is VERY hard to find. Thank you for writing it!

      -1
    2. 52

      CSS specificity is probably the worst aspect of what Douglas Crockford rightly terms, “Crappy Style Sheet System”. I think the authors of the spec went a little overboard in trying to make CSS clever. Instead, it is an overly complicated piece of crap that, by its very design, leads to bloat and error.

      As an example of its failure, consider this case. I want to use jQuery’s tab control. It comes with some default styles to structure it. It has a class called .ui-corner-all that is applied to the outer-most div. It makes the corners rounded if the browser supports it. I don’t want that and wish to override. But, I DO want it elsewhere. So, I wrap the tabs I want to override in a div with an ID and attempt to override as such.

      #user-content-box .ui-corner-all

      This does not work. Given that by default there is only .ui-corner-all on the tab div, the above should be more specific with a parent introduced in the hierarchy.

      So, div.ui-corner-all has more specificity than #user-content-box .ui-corner-all. That is idiotic, and certainly unintuitive.

      #user-content-box div.ui-corner-all is what works, but we must add more information than is needed, thus leading to bloat.

      -2
    3. 103

      Sweet…
      I love it. thanks for this tutorial!
      Better explained than any other book
      I have read.

      0
    4. 154

      Really nice…

      -1
    5. 205

      Stop trying to be clever about it,this is nothing more than abuse of css. PERIOD.

      0
    6. 256

      Hi. I try to understand your problem…

      But for me, it looks like you are doing something wrong.
      I have no problems, on override some tabs Style separatly.

      But one other idea for you, if you don’t want the ui-corner-all class on a specific DOM, why you don’t use jQuery to just remove the class, i think that would be the simplest solution:
      $(“#tabs”).removeClass(“ui-corner-all”);

      Regards Cyclo

      -1
    7. 307

      What an excellent tutorial! Using the stormtroopers gave it a feel like… I don’t know… A trading card game perhaps? I don’t know.
      I only had an issue with one thing. The contextual selectors.
      Here is an example in order:
      Which one wins?:
      CSS:

      ul ol { padding: 3px }

      ol { padding: 4px}

      ul { padding: 2px; }

      end of CSS

      Understanding that more precise, contextual selectors should win the argument, I would say that number one would win. If I am wrong please say so and state why.
      Thank you so much for this amazing tutorial.

      1
    8. 358

      Assuming a structure of:

      <ul>
       <li>
        <ol>
        </ol>
       </li>
      </ul>

      Then your “ul ol” wins for the ol, and your “ul” wins for the parent ul. This is where context comes in. The declaration that wins depends on the context in which the element appears.

      “ul ol” says “for OLs within ULs, add these styles”. If the ol is not in a ul, then it doesn’t match the criteria for “ul ol”.

      0
    9. 409

      Thanks for the article, but why did you put the glossary of terms — terms that you use all throughout your article — at the END of your article?! Sure, folks who live and breathe this stuff know the definitions, but if your intention is to educate, then you might do well to lay the ground work before you begin.
      Thanks.

      0
    10. 460

      You can also unserstand CSS Specificity if you like fish: http://www.standardista.com/css3/css-specificity/

      0
    11. 511

      Don’t know if this has been covered in the comments but under the “What is what?” section, and then under “attribute selector”, I believe “p span” should be “p[title]” :P

      0
    12. 562

      Allasso Travesser

      August 6, 2013 5:02 am

      “Start at 0, add 1000 for style attribute, add 100 for each ID, add 10 for each attribute, class or pseudo-class, add 1 for each element name or pseudo-element.”

      Does this mean that if I assign 101 classes to an element, and have a style testing for all 101 classes, that this style will override same style declaration in a style attribute?

      (101 x 10 > 1000)

      or that 11 classes will override an ID?

      (11 x 10 > 100)

      Ridiculous examples indeed, but I am challenging the literal accuracy of the assertions here.

      0
    13. 613

      Agustin Giannastasio

      August 13, 2013 4:48 pm

      Great article! 6 years now since published and still so current and useful. Need to share this with most Front-Ends I know.

      0
    14. 664

      Correct me if I’m wrong, but it looks like you forgot to mention an important detail about selectors specificity, which lead to a lot of confusion. Quoting straight from the spec:

      “Concatenating the four numbers a-b-c-d ***(in a number system with a large base)*** gives the specificity.”
      (Source: http://www.w3.org/TR/CSS2/cascade.html#specificity)

      As I understand it, one should imagine this number written in a very large (if not infinite) base. Example:
      Specificity #1: a=0, b=0, c=10, d=0. This gives someting like 00a0 (base 16).
      Specificity #2: a=0, b=1, c=9, d=0. This gives someting like 0190 (base 16).

      I used base 16 because it is familiar to many. The point is to understand that as long as a value differs from 0, it is always more significative than every value on its right (above, #2 wins against #1 because b’s value differs from 0 and thus wins against every value c or d could have. c’s value never influences b’s value)

      0
    15. 715

      very interesting and useful article. thnx.

      0
    16. 766

      Thanks for this complete article!

      A funny fact is the difference between theory & practice.
      In theory, an ID is greater than an infinity of classes.
      In practice, browser use a counter, so 256 classes override an ID.
      (Source: http://www.thecssninja.com/css/extreme-specificity)

      I also use a different system, more human-friendly, when I want to share a specificity with another developer: http://tzi.fr/CSS/Selector/Meaningful-selector-specificity-measure

      Cheers,
      Thomas.

      0
    17. 817

      @new question:
      Hi ,

      Please have look at my plunker, why the span element always takes color:#00f; http://plnkr.co/edit/UkmTsWdYHYI7818jCXzO?p=preview

      #x span{//Id =100, span 1 ==> 101
      color:#00f;
      }

      h1.a.b.c.d.e.f.g.h.i.j.k.l.m.n span{//class=140+2==>142
      color:#f00;
      }
      Though the specificity of the class selector is high but still id selector getting applied. Please clarify.

      0
    18. 868

      I got the answer for my question. Looks all theoretical here. Based on the browser it varies. Specificity entirely depends on the way the browser save it(8 bit / 16 bit).

      Thanks @tzi

      0
    19. 919

      This “add 10 for each attribute” is not accurate, we should be mindful of this case:
      If we have 11 attributes, they still won’t trump a single id, although 11*10 = 110 > 100.

      0
    20. 970

      An “id” will trump ANY number of classes.
      So in your case, #x, being an id, will outweight any number of classes (in your case 14 classes)

      0
    21. 1021

      @Peter #15

      Exactly, there are a million guides for calculating specificity that then show one level deep css theming. Show me the magic working on a user icon nested in a sidebar table field….

      0
    22. 1072

      While it should be made more clear here, that text is actually an excerpt from the linked article. I don’t think Mr. Friedman was intentionally trying to say that he created the chart.

      0
    23. 1123

      that, I realize there are still a lot of pepole using IE6 and IE7, which cause most of the headaches. According to , they represented 35% of browser use in December. I highlight the main problems with those two browsers, and show how to resolve them. But the general advice I give in the book is not to try to solve every issue with IE6 and IE7.The important thing is that your content remains accessible to users of older browsers. Style your pages to work in a standards-compliant browser, and then fix the major problems for IE6 and IE7. Ignore any differences that don’t affect overall readability, even if they don’t look quite the way you would like. Many pepole are now accessing the web on mobile devices, which often display content differently to avoid the need for horizontal scrolling. The idea that pages should look identical in every browser and on every device is impractical.

      0

    ↑ Back to top