Selectores CSS
Referencia rápida de todos los selectores CSS
Basic Selectors
| Selector | Description | Example |
|---|---|---|
*
|
Universal selector — matches every element | * { box-sizing: border-box; } |
div
|
Type selector — matches all elements of a given tag name | p { color: #333; } |
.class
|
Class selector — matches elements with this class attribute | .btn { padding: 8px 16px; } |
#id
|
ID selector — matches the element with this unique id | #header { height: 60px; } |
.class1.class2
|
Multiple classes — matches elements having both classes | .btn.btn-primary { background: blue; } |
div, p, span
|
Selector list (group) — matches any element in the list | h1, h2, h3 { font-family: sans-serif; } |
div.class
|
Type + class — matches div elements with this class | a.active { font-weight: bold; } |
div#id
|
Type + ID — matches div element with this specific ID | section#main { max-width: 1200px; } |
:root
|
Matches the root element (html in HTML documents) | :root { --primary: #007bff; } |
html
|
Matches the top-level html element | html { font-size: 16px; } |
Combinators
| Selector | Description | Example |
|---|---|---|
A B
|
Descendant combinator — B anywhere inside A | nav a { color: white; } |
A > B
|
Child combinator — B that is a direct child of A | ul > li { list-style: disc; } |
A + B
|
Adjacent sibling combinator — B immediately after A | h1 + p { margin-top: 0; } |
A ~ B
|
General sibling combinator — all B siblings after A | h2 ~ p { color: #666; } |
A || B
|
Column combinator — B within a table column A (CSS Grid Level 1) | col.selected || td { background: yellow; } |
Pseudo-classes
| Selector | Description | Example |
|---|---|---|
:hover
|
Matches when the user hovers the mouse over the element | a:hover { text-decoration: underline; } |
:focus
|
Matches when the element is focused (keyboard/click) | input:focus { outline: 2px solid blue; } |
:focus-visible
|
Matches focus only when it should be visually indicated | button:focus-visible { outline: 3px solid orange; } |
:active
|
Matches when the element is being activated (clicked) | button:active { transform: scale(0.98); } |
:visited
|
Matches anchor links that have been visited | a:visited { color: purple; } |
:link
|
Matches unvisited anchor links | a:link { color: blue; } |
:checked
|
Matches checked checkboxes, radio buttons, or options | input:checked + label { font-weight: bold; } |
:disabled
|
Matches form elements that are disabled | input:disabled { opacity: 0.5; } |
:enabled
|
Matches form elements that are enabled | input:enabled { border-color: #ccc; } |
:required
|
Matches form elements with the required attribute | input:required { border-left: 3px solid red; } |
:optional
|
Matches form elements without the required attribute | input:optional { border-color: #eee; } |
:valid
|
Matches form elements whose value is valid | input:valid { border-color: green; } |
:invalid
|
Matches form elements whose value is invalid | input:invalid { border-color: red; } |
:placeholder-shown
|
Matches an input element displaying placeholder text | input:placeholder-shown { font-style: italic; } |
:first-child
|
Matches an element that is the first child of its parent | li:first-child { border-top: none; } |
:last-child
|
Matches an element that is the last child of its parent | li:last-child { margin-bottom: 0; } |
:nth-child(n)
|
Matches elements based on their position among siblings | tr:nth-child(even) { background: #f5f5f5; } |
:nth-last-child(n)
|
Matches elements counting from the last sibling | li:nth-last-child(2) { color: red; } |
:first-of-type
|
Matches the first sibling of its type | p:first-of-type { font-size: 1.2em; } |
:last-of-type
|
Matches the last sibling of its type | p:last-of-type { margin-bottom: 0; } |
:nth-of-type(n)
|
Matches siblings of its type at position n | p:nth-of-type(odd) { background: #fafafa; } |
:only-child
|
Matches an element that is the only child of its parent | li:only-child { list-style: none; } |
:only-of-type
|
Matches an element that is the only sibling of its type | img:only-of-type { display: block; margin: auto; } |
:empty
|
Matches elements that have no children or text | div:empty { display: none; } |
:not(selector)
|
Negation pseudo-class — matches elements that do not match | input:not([type=submit]) { border: 1px solid #ccc; } |
:is(selector-list)
|
Matches any element in the selector list (forgiving) | :is(h1, h2, h3) { line-height: 1.2; } |
:where(selector-list)
|
Like :is() but with zero specificity | :where(header, footer) a { color: inherit; } |
:has(selector)
|
Matches parent if it contains the given selector | div:has(img) { padding: 0; } |
:target
|
Matches the element whose id matches the URL fragment | :target { background: yellow; } |
:lang(code)
|
Matches elements with a specific language attribute | :lang(fr) { font-style: italic; } |
Pseudo-elements
| Selector | Description | Example |
|---|---|---|
::before
|
Inserts content before the element's actual content | .quote::before { content: '\201C'; } |
::after
|
Inserts content after the element's actual content | .required::after { content: ' *'; color: red; } |
::first-line
|
Matches the first line of a block-level element | p::first-line { font-weight: bold; } |
::first-letter
|
Matches the first letter of a block-level element | p::first-letter { font-size: 2em; float: left; } |
::selection
|
Matches the portion of text selected by the user | ::selection { background: #005fcc; color: white; } |
::placeholder
|
Matches the placeholder text of form inputs | input::placeholder { color: #aaa; font-style: italic; } |
::marker
|
Matches the marker box of a list item (bullet/number) | li::marker { color: red; font-size: 1.2em; } |
::backdrop
|
Matches the backdrop behind dialog or fullscreen elements | dialog::backdrop { background: rgba(0,0,0,0.5); } |
::file-selector-button
|
Matches the button of a file input element | input[type=file]::file-selector-button { padding: 4px 8px; } |
Attribute Selectors
| Selector | Description | Example |
|---|---|---|
[attr]
|
Matches elements with the attribute present (any value) | [disabled] { opacity: 0.5; } |
[attr=value]
|
Matches elements where attr equals value exactly | [type=submit] { background: blue; } |
[attr~=value]
|
Matches elements where attr contains value as a whole word in a space-separated list | [class~=btn] { cursor: pointer; } |
[attr|=value]
|
Matches elements where attr equals value or starts with value- (for language codes) | [lang|=en] { font-family: Georgia; } |
[attr^=value]
|
Matches elements where attr starts with value | a[href^=https] { color: green; } |
[attr$=value]
|
Matches elements where attr ends with value | a[href$=.pdf]::after { content: ' (PDF)'; } |
[attr*=value]
|
Matches elements where attr contains value as a substring | a[href*=example] { color: orange; } |
[attr=value i]
|
Case-insensitive attribute value matching | [type=TEXT i] { border: 1px solid #ccc; } |
[attr=value s]
|
Case-sensitive attribute value matching (explicit) | [data-theme=Dark s] { background: #000; } |
Preguntas Frecuentes
La especificidad CSS determina qué regla de estilo tiene prioridad cuando varias reglas apuntan al mismo elemento. Se calcula como un valor de cuatro partes (inline, IDs, clases/atributos/pseudo-clases, elementos/pseudo-elementos). Los estilos inline puntúan (1,0,0,0). Los selectores de ID (#id) puntúan (0,1,0,0). Los selectores de clase, de atributo y las pseudo-clases puntúan (0,0,1,0). Los selectores de elemento y los pseudo-elementos puntúan (0,0,0,1). Gana el selector con mayor especificidad. Cuando la especificidad es igual, gana la regla que aparece más tarde en la hoja de estilos. La declaración !important anula todas las reglas de especificidad.
Los dos puntos simples (:) designan pseudo-clases, que seleccionan elementos según su estado o posición — por ejemplo :hover, :focus, :nth-child() o :not(). Los dos puntos dobles (::) designan pseudo-elementos, que seleccionan y dan estilo a una parte concreta de un elemento — por ejemplo ::before, ::after, ::first-line o ::placeholder. La sintaxis de dos puntos dobles se introdujo en CSS3 para distinguir los pseudo-elementos de las pseudo-clases. Por compatibilidad con versiones anteriores, la mayoría de los navegadores siguen aceptando dos puntos simples para pseudo-elementos antiguos como :before y :after.
:nth-child(n) selecciona un elemento que es el hijo número n de su padre, independientemente del tipo de elemento. Por tanto, p:nth-child(2) selecciona un
solo si es el segundo hijo de su padre. :nth-of-type(n) selecciona el n-ésimo hermano del mismo tipo de elemento. Así, p:nth-of-type(2) selecciona el segundo
entre sus hermanos, sin importar su posición entre otros tipos de elementos. En la práctica, :nth-of-type() suele ser más predecible cuando hay tipos de elementos mezclados dentro de un contenedor.
Los selectores de atributo coinciden con elementos según la presencia o el valor de sus atributos HTML. [attr] selecciona elementos que tienen el atributo. [attr="valor"] selecciona elementos donde el atributo es exactamente igual al valor. [attr^="valor"] coincide si el atributo empieza por ese valor. [attr$="valor"] coincide si termina por ese valor. [attr*="valor"] coincide si el atributo contiene el valor en cualquier posición. [attr~="valor"] coincide si el atributo es una lista separada por espacios que contiene el valor. Por ejemplo, a[href^="https"] apunta a todos los enlaces que empiezan por "https".
Sí. Puedes combinar selectores de varias formas. La agrupación (A, B) aplica los mismos estilos a varios selectores. El encadenamiento (A.B o A:hover) apunta a un elemento que cumple todas las condiciones a la vez — por ejemplo, div.active coincide con un
con la clase "active". Los combinadores definen relaciones: un espacio (A B) apunta a descendientes, > (A > B) a hijos directos, + (A + B) al hermano adyacente inmediato y ~ (A ~ B) a todos los hermanos siguientes. Combinar estas técnicas permite escribir reglas muy específicas sin necesitar clases o IDs adicionales.