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These docs are old and won’t be updated. Go to react.dev for the new React docs.

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These new documentation pages teach modern React and include live examples:

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React implements a browser-independent DOM system for performance and cross-browser compatibility. We took the opportunity to clean up a few rough edges in browser DOM implementations.

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In React, all DOM properties and attributes (including event handlers) should be camelCased. For example, the HTML attribute tabindex corresponds to the attribute tabIndex in React. The exception is aria-* and data-* attributes, which should be lowercased. For example, you can keep aria-label as aria-label.

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Differences In Attributes

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There are a number of attributes that work differently between React and HTML:

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checked

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The checked attribute is supported by <input> components of type checkbox or radio. You can use it to set whether the component is checked. This is useful for building controlled components. defaultChecked is the uncontrolled equivalent, which sets whether the component is checked when it is first mounted.

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className

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To specify a CSS class, use the className attribute. This applies to all regular DOM and SVG elements like <div>, <a>, and others.

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If you use React with Web Components (which is uncommon), use the class attribute instead.

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dangerouslySetInnerHTML

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dangerouslySetInnerHTML is React’s replacement for using innerHTML in the browser DOM. In general, setting HTML from code is risky because it’s easy to inadvertently expose your users to a cross-site scripting (XSS) attack. So, you can set HTML directly from React, but you have to type out dangerouslySetInnerHTML and pass an object with a __html key, to remind yourself that it’s dangerous. For example:

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function createMarkup() {\n  return {__html: 'First &middot; Second'};\n}\n\nfunction MyComponent() {\n  return <div dangerouslySetInnerHTML={createMarkup()} />;\n}
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htmlFor

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Since for is a reserved word in JavaScript, React elements use htmlFor instead.

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onChange

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The onChange event behaves as you would expect it to: whenever a form field is changed, this event is fired. We intentionally do not use the existing browser behavior because onChange is a misnomer for its behavior and React relies on this event to handle user input in real time.

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selected

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If you want to mark an <option> as selected, reference the value of that option in the value of its <select> instead.\nCheck out “The select Tag” for detailed instructions.

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style

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Note

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Some examples in the documentation use style for convenience, but using the style attribute as the primary means of styling elements is generally not recommended. In most cases, className should be used to reference classes defined in an external CSS stylesheet. style is most often used in React applications to add dynamically-computed styles at render time. See also FAQ: Styling and CSS.

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The style attribute accepts a JavaScript object with camelCased properties rather than a CSS string. This is consistent with the DOM style JavaScript property, is more efficient, and prevents XSS security holes. For example:

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const divStyle = {\n  color: 'blue',\n  backgroundImage: 'url(' + imgUrl + ')',\n};\n\nfunction HelloWorldComponent() {\n  return <div style={divStyle}>Hello World!</div>;\n}
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Note that styles are not autoprefixed. To support older browsers, you need to supply corresponding style properties:

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const divStyle = {\n  WebkitTransition: 'all', // note the capital 'W' here\n  msTransition: 'all' // 'ms' is the only lowercase vendor prefix\n};\n\nfunction ComponentWithTransition() {\n  return <div style={divStyle}>This should work cross-browser</div>;\n}
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Style keys are camelCased in order to be consistent with accessing the properties on DOM nodes from JS (e.g. node.style.backgroundImage). Vendor prefixes other than ms should begin with a capital letter. This is why WebkitTransition has an uppercase “W”.

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React will automatically append a “px” suffix to certain numeric inline style properties. If you want to use units other than “px”, specify the value as a string with the desired unit. For example:

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// Result style: '10px'\n<div style={{ height: 10 }}>\n  Hello World!\n</div>\n\n// Result style: '10%'\n<div style={{ height: '10%' }}>\n  Hello World!\n</div>
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Not all style properties are converted to pixel strings though. Certain ones remain unitless (eg zoom, order, flex). A complete list of unitless properties can be seen here.

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suppressContentEditableWarning

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Normally, there is a warning when an element with children is also marked as contentEditable, because it won’t work. This attribute suppresses that warning. Don’t use this unless you are building a library like Draft.js that manages contentEditable manually.

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suppressHydrationWarning

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If you use server-side React rendering, normally there is a warning when the server and the client render different content. However, in some rare cases, it is very hard or impossible to guarantee an exact match. For example, timestamps are expected to differ on the server and on the client.

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If you set suppressHydrationWarning to true, React will not warn you about mismatches in the attributes and the content of that element. It only works one level deep, and is intended to be used as an escape hatch. Don’t overuse it. You can read more about hydration in the ReactDOM.hydrateRoot() documentation.

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value

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The value attribute is supported by <input>, <select> and <textarea> components. You can use it to set the value of the component. This is useful for building controlled components. defaultValue is the uncontrolled equivalent, which sets the value of the component when it is first mounted.

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All Supported HTML Attributes

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As of React 16, any standard or custom DOM attributes are fully supported.

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React has always provided a JavaScript-centric API to the DOM. Since React components often take both custom and DOM-related props, React uses the camelCase convention just like the DOM APIs:

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<div tabIndex={-1} />      // Just like node.tabIndex DOM API\n<div className=\"Button\" /> // Just like node.className DOM API\n<input readOnly={true} />  // Just like node.readOnly DOM API
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These props work similarly to the corresponding HTML attributes, with the exception of the special cases documented above.

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Some of the DOM attributes supported by React include:

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accept acceptCharset accessKey action allowFullScreen alt async autoComplete\nautoFocus autoPlay capture cellPadding cellSpacing challenge charSet checked\ncite classID className colSpan cols content contentEditable contextMenu controls\ncontrolsList coords crossOrigin data dateTime default defer dir disabled\ndownload draggable encType form formAction formEncType formMethod formNoValidate\nformTarget frameBorder headers height hidden high href hrefLang htmlFor\nhttpEquiv icon id inputMode integrity is keyParams keyType kind label lang list\nloop low manifest marginHeight marginWidth max maxLength media mediaGroup method\nmin minLength multiple muted name noValidate nonce open optimum pattern\nplaceholder poster preload profile radioGroup readOnly rel required reversed\nrole rowSpan rows sandbox scope scoped scrolling seamless selected shape size\nsizes span spellCheck src srcDoc srcLang srcSet start step style summary\ntabIndex target title type useMap value width wmode wrap
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Similarly, all SVG attributes are fully supported:

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accentHeight accumulate additive alignmentBaseline allowReorder alphabetic\namplitude arabicForm ascent attributeName attributeType autoReverse azimuth\nbaseFrequency baseProfile baselineShift bbox begin bias by calcMode capHeight\nclip clipPath clipPathUnits clipRule colorInterpolation\ncolorInterpolationFilters colorProfile colorRendering contentScriptType\ncontentStyleType cursor cx cy d decelerate descent diffuseConstant direction\ndisplay divisor dominantBaseline dur dx dy edgeMode elevation enableBackground\nend exponent externalResourcesRequired fill fillOpacity fillRule filter\nfilterRes filterUnits floodColor floodOpacity focusable fontFamily fontSize\nfontSizeAdjust fontStretch fontStyle fontVariant fontWeight format from fx fy\ng1 g2 glyphName glyphOrientationHorizontal glyphOrientationVertical glyphRef\ngradientTransform gradientUnits hanging horizAdvX horizOriginX ideographic\nimageRendering in in2 intercept k k1 k2 k3 k4 kernelMatrix kernelUnitLength\nkerning keyPoints keySplines keyTimes lengthAdjust letterSpacing lightingColor\nlimitingConeAngle local markerEnd markerHeight markerMid markerStart\nmarkerUnits markerWidth mask maskContentUnits maskUnits mathematical mode\nnumOctaves offset opacity operator order orient orientation origin overflow\noverlinePosition overlineThickness paintOrder panose1 pathLength\npatternContentUnits patternTransform patternUnits pointerEvents points\npointsAtX pointsAtY pointsAtZ preserveAlpha preserveAspectRatio primitiveUnits\nr radius refX refY renderingIntent repeatCount repeatDur requiredExtensions\nrequiredFeatures restart result rotate rx ry scale seed shapeRendering slope\nspacing specularConstant specularExponent speed spreadMethod startOffset\nstdDeviation stemh stemv stitchTiles stopColor stopOpacity\nstrikethroughPosition strikethroughThickness string stroke strokeDasharray\nstrokeDashoffset strokeLinecap strokeLinejoin strokeMiterlimit strokeOpacity\nstrokeWidth surfaceScale systemLanguage tableValues targetX targetY textAnchor\ntextDecoration textLength textRendering to transform u1 u2 underlinePosition\nunderlineThickness unicode unicodeBidi unicodeRange unitsPerEm vAlphabetic\nvHanging vIdeographic vMathematical values vectorEffect version vertAdvY\nvertOriginX vertOriginY viewBox viewTarget visibility widths wordSpacing\nwritingMode x x1 x2 xChannelSelector xHeight xlinkActuate xlinkArcrole\nxlinkHref xlinkRole xlinkShow xlinkTitle xlinkType xmlns xmlnsXlink xmlBase\nxmlLang xmlSpace y y1 y2 yChannelSelector z zoomAndPan
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You may also use custom attributes as long as they’re fully lowercase.

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