The HTML standard doesn't list what image formats to support, so each user agent supports different formats. A complete guide to image formats supported by web browsers is available. The abbreviation for each format links to a longer description of the format, its capabilities, and detailed browser compatibility information; including which versions introduced support and specific special features that may have been introduced later.
If an error occurs while loading or rendering an image, and an onerror event handler has been set on the error event, that event handler will get called. This can happen in a number of situations, including:. In these cases, the browser may replace the image with the text in the element's alt attribute. For these reasons and others, provide a useful value for alt whenever possible. Omitting alt altogether indicates that the image is a key part of the content and no textual equivalent is available.
Visual browsers will also hide the broken image icon if the alt is empty and the image failed to display. This attribute is also used when copying and pasting the image to text, or saving a linked image to a bookmark.
The browser may use its own heuristics to prioritize the image. This gives users without pointing devices a fallback destination.
Media Conditions describe properties of the viewportnot of the image. For example, max-height: px px proposes to use a source of px width, if the viewport is not higher than px. Source size values specify the intended display size of the image.
User agents use the current source size to select one of the sources supplied by the srcset attribute, when those sources are described using width w descriptors. If the srcset attribute is absent, or contains no values with a width descriptor, then the sizes attribute has no effect. It is incorrect to mix width descriptors and pixel density descriptors in the same srcset attribute. Duplicate descriptors for instance, two sources in the same srcset which are both described with 2x are also invalid.
The user agent selects any of the available sources at its discretion. This provides them with significant leeway to tailor their selection based on things like user preferences or bandwidth conditions. See our Responsive images tutorial for an example. Depending on its type, an image may have an intrinsic width and height.
For some image types, however, intrinsic dimensions are unnecessary. The following example embeds an image into the page and includes alternative text for accessibility.
This example builds upon the previous one, showing how to turn the image into a link. You should made the alternative text describe the resource the link is pointing to, as if you were using a text link instead. In this example we include a srcset attribute with a reference to a high-resolution version of the logo; this will be loaded instead of the src image on high-resolution devices. The image referenced in the src attribute is counted as a 1x candidate in user agents that support srcset.
The src attribute is ignored in user agents that support srcset when w descriptors are included. When the max-width: px media condition matches, the pixel-wide image will load it is the one that matches px most closelyotherwise the other image will load. To see the resizing in action, view the example on a separate pageso you can actually resize the content area.
See Referer header: privacy and security concerns for more information and mitigations. An alt attribute's value should clearly and concisely describe the image's content. It should not describe the presence of the image itself or the file name of the image.
If the alt attribute is purposefully left off because the image has no textual equivalent, consider alternate methods to present what the image is trying to communicate. When an alt attribute is not present on an image, some screen readers may announce the image's file name instead.The following element embeds an image into the document.
The compatibility table in this page is generated from structured data. Get the latest and greatest from MDN delivered straight to your inbox. Sign in to enjoy the benefits of an MDN account. The colon is required, single quotes shouldn't be used. You can also specify data schemas not recommended. This is insecure; an attacker can also inject arbitrary data: URIs. Use this sparingly and definitely not for scripts.
The server must generate a unique nonce value each time it transmits a policy. See unsafe inline script for an example. Specifying nonce makes a modern browser ignore 'unsafe-inline' which could still be set for older browsers without nonce support. The use of this source consists of two portions separated by a dash: the encryption algorithm used to create the hash and the baseencoded hash of the script or style.
In CSP 2. CSP 3. At the same time, any whitelist or source expressions such as 'self' or 'unsafe-inline' will be ignored. See script-src for an example. Last modified: Jul 14,by MDN contributors. Related Topics. Sites can use this to avoid clickjacking attacks, by ensuring that their content is not embedded into other sites.
If this value is absent, then any URI is allowed. For workers, non-compliant requests are treated as fatal network errors by the user agent. This is an enforcement on what navigations this document initiates not on what this document is allowed to navigate to.
Responsive Images in CSS
It applies restrictions to a page's actions including preventing popups, preventing the execution of plugins and scripts, and enforcing a same-origin policy. Learn the best of web development Get the latest and greatest from MDN delivered straight to your inbox. The newsletter is offered in English only at the moment.The src attribute identifies an image by a URL.
The image defined by the URL is retrieved by the browser and inserted into the document when the page loads. This is the most straightforward, and is the only way to go if you want to link to an external image an image hosted on another site. Hotlinking is sometimes just fine.
For instance, in the above example we hotlinked an image from Wikimedia Commons. This is a Public Domain image hosted by a media provider. No problem. However, it can be a problem in certain circumstances. First of all, if the image in question is under copyright, and you do not have permission to use it, you may be in violation of copyright laws by hotlinking.
Because you aren't actually putting the image on your site, there is a bit of a legal gray area here, but it is at least potentially a problem.
Related to that, even if isn't illegal, it may be immoral or unethical if you know that the image owner does not want you to hotlink their pictures. Finally, if you don't control the hotlinked image, it might change. Sometimes this just happens because sites go down or get rearranged.
However, sometimes a perturbed site owner will deliberately change an image in response to hotlinking. Hotlinking to an image hosting service is just fine, and it's also reasonable to hotlink an image in a casual conversation on a forum or blog comment. But if an image is an integral part of your content even if the content is a link to the image's original sourceyou really should save the image to your own server.
Protip: If you want to block others from hotlinking your images, you can do so with. A relative URL does not include the domain name, and is relative to either the current page, or the current domain. If you begin with a slash, it will be relative to the domain. It is almost always the best idea to use source URLs which are relative to the domain, not the page. They will not break if the page content is moved or copied.
This way, the URLs won't break when you change domains which will happen automatically if you use a development or staging server in addition to your production one. It is possible to encode content into a URI string. You then use the string as if it were a URL, and then the browser simply interprets it as if it were a file. It's weird and kinda neat:. You need a special encoding program to turn images or other files into Data URIs.
The one above was created with this tool. Data URIs are not usually a great solution. Most meaningful images are going to create insanely long strings just see the example aboveand they actually don't load as fast as external files.
They do cut down on HTTP requests to the server, which you may or may not care about. They can also be useful in situations where external images might not get loaded, such as in emails or in self-contained documents to be read offline. Each browser supports a slightly different set of image file types. This used to be a serious problem for designers Internet Explorer would not display PNG files correctly until v8, and SVG wasn't supported until v9but most of those issues have calmed down as all the major browsers have basically caught up with each other.Learn Development at Frontend Masters.
But how do the capabilities that these things provide map to CSS? Responsive images was, in a sense, just catching up to what CSS could already do. One image for 1x displays, a larger image for 2x displays. If we wanted to do that same thing, only as a background-image in CSS, we could do:.
There is a difference here, though. The attribute and value provide information about what is available and the browser decides what is best at the moment. Or at least, it couldif browsers chose to implement it that way. With a media query, what is declared shall be. According to the still in draft spec :.
: The Image Embed element
The image-set function allows an author to ignore most of these issues, simply providing multiple resolutions of an image and letting the UA decide which is most appropriate in a given situation. You pair it with srcsetwhich provides known widths, so the browser can make a choice. The information in the markup above gives the browser what it needs to figure out the best image for it.
It now also knows it will be displaying this image at vw. So it has to pick between the two images provided. It does some math. Now say it was a 2x display. That doubles the amount of pixels needed to show the images, so the math is:.
How about a 1x display with a px viewport? This is kinda weird and tricky to write out in CSS. If we just think about 1x displays, we end up with logic like….
In this exact case, a 2x display, even at a really narrow width like px, still requires px make that 1. The complexity of this skyrockets the more breakpoints sizes and the more provided images. This kind of thing is a fairly straight-forward conversion to media queries. The exact media queries are right there to copy:. Again, this is just waiting to blow up in complexity as you add a few more images and conditions. Slightly better with image-set :.
Maybe there is even a way to combine resolution queries and image-set syntaxes? Perhaps even in a middle-ground kinda way of just swapping out larger images at large breakpoints? Laying out designs on the web with CSS has gotten a lot more powerful in recent years.As shown below.
We have four divs of different sizes and width,height of divs are applied through css as shown below. In last div we gave width and height of div element greater than that our image size, in this case the image will not be auto resized and displayed as its i.
In the above examples Image will be fit into parent div element without scaling it. In first div width is 50px and height is 80px i. And in second div height is 30px and width is 80px. Maximum image height can be only 30px and width is adjusted to 30px. In the last div i. So displayed as it is. And add the object-fit property value as contain.
But the difference is if parent div size is more than image size then image will be automatically resized to parent div element size. The clarity of the image will be reduced. See the below Demo. Auto resize image using CSS Demo. Wait before leaving. I am One among a million Software engineers of India. I write beautiful markup. I make the Web useful.
Arunkumar Blog Home Posts. Arunkumar Gudelli. In third div i. See the below Demo Auto resize image using css Demo example: Go through the demo and understand difference between both css and css3 way.Learn Development at Frontend Masters.
The following is a guest post by Marcel Shields. Also turns out to be a pretty good way to replace anything with an image. I just wanted to share something I found really cool about using CSS box-sizing. It makes things a lot more sane when thinking about layout.
People love it so much, they put it on everything like hot sauce. I wanted to share how I found it useful as yet another image replacement technique.
After a few iterations in Chrome Dev Tools, I thought to use the box-sizing property to keep dimensions strict, add the new image as a background image, and just push the inline image out of the way with padding and see what happened.
That last point seemed important, as it works really well for text replacement too without any adjustment. Check it out! Frontend Masters is the best place to get it. Thanks for your comment. I might have been a little bit scared to lose a finger, but I promise you no animals were harmed! No real reason against it that I can think of.
Honestly, I just found this way to be a sort of multi-use option. And yeah, pseudo elements were attempted with the unfortunate results. Worked like a charm in Chrome. I always thought that was a mistake it worked in some browser.
Just my point of view :. For images, it looks like an awesome solution! The only thing I noticed with the text substitution is that the old text remains selectable. Not a huge problem, but in some cases it might be.
For text replacement I usually use:. Using display:none; has no negative SEO impact whatsoever, it probably never will, at least for many, many years from now.
Check this forum out at Stackexchange. If at least you could reference our discussion in the article so people can decide on their own if using display:none; is right for them or not…. It might be interesting to make a code snippet or WordPress plugin that handles retina images this way. The CSS just needs to be wrapped in a media query.
To center an image, set left and right margin to auto and make it into a block element:. The opacity property can take a value from 0. The lower value, the more transparent:. The CSS filter property adds visual effects like blur and saturation to an element.
CSS can be used to create image galleries. This example use media queries to re-arrange the images on different screen sizes.
Example Slide in top : Hello World. Example Slide in bottom : Hello World. Example Slide in left : Hello World. Example Slide in right : Hello World. Add a description of the image here. HOW TO. Your message has been sent to W3Schools.