Image aspect ratio
Images display at their intended proportions.
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Impact
About
Image aspect ratio is the relationship between an image's width and height. It's expressed as two numbers, like 16:9 or 4:3. For example, a 16:9 aspect ratio means the width is 16 units wide for every 9 units of height. Aspect ratio helps ensure images look good on different screens, like phones, computers, and TVs. Using the correct ratio prevents stretching or squishing the image and maintains its quality.
Why it's important
Ensures images display correctly without distortion on different screens and devices.
User stories
As a user, I want the website to display images at the correct aspect ratio so that I can read and interact with the content without distortion.
Code
Failing pattern:
<!-- Fail: explicit dimensions that distort the image -->
<img src="logo.png" width="300" height="50">
Passing pattern:
<!-- Pass: set one dimension and let the other scale -->
<img src="logo.png" width="300" height="auto">
<!-- Or in CSS -->
img { max-width: 100%; height: auto; }
Error
ScanGov messaging when a site fails a standard:
Image could not be displayed correctly due to aspect ratio issues.
Guidance
Links
Indicators
Related
- [accesskey] values are unique
- [aria-*] attributes match their roles
- Uses ARIA roles only on compatible elements
- button, link, and menuitem elements have accessible names
- ARIA attributes are used as specified for the element's role
- Deprecated ARIA roles were not used
- Elements with role="dialog" or role="alertdialog" have accessible names
- [aria-hidden="true"] is not present on the document <body>
- [aria-hidden="true"] elements do not contain focusable descendents
- ARIA input fields have accessible names
- ARIA meter elements have accessible names
- ARIA progressbar elements have accessible names
- Elements use only permitted ARIA attributes
- [role]s have all required [aria-*] attributes
- Elements with an ARIA [role] that require children to contain a specific [role] have all required children
- [role]s are contained by their required parent element
- [role] values are valid
- Elements with the role=text attribute do not have focusable descendents
- ARIA toggle fields have accessible names
- ARIA tooltip elements have accessible names
- ARIA treeitem elements have accessible names
- [aria-*] attributes have valid values
- [aria-*] attributes are valid and not misspelled
- Buttons have an accessible name
- The page contains a heading, skip link, or landmark region
- Background and foreground colors have a sufficient contrast ratio
- <dl>'s contain only properly-ordered <dt> and <dd> groups, <script>, <template> or <div> elements
- Definition list items are wrapped in <dl> elements
- Document has a <title> element
- ARIA IDs are unique
- No form fields have multiple labels
- <frame> or <iframe> elements have a title
- Heading elements appear in a sequentially-descending order
- <html> element has a [lang] attribute
- <html> element has a valid value for its [lang] attribute
- <html> element has an [xml:lang] attribute with the same base language as the [lang] attribute
- Image elements have [alt] attributes
- Image elements do not have [alt] attributes that are redundant text
- Input buttons have discernible text
- <input type="image"> elements have [alt] text
- Form elements have associated labels
- Links are distinguishable without relying on color
- Links have a discernible name
- Lists contain only <li> elements and script supporting elements (<script> and <template>)
- List items (<li>) are contained within <ul>, <ol> or <menu> parent elements
- The document does not use <meta http-equiv="refresh">
- [user-scalable="no"] is not used in the <meta name="viewport"> element and the [maximum-scale] attribute is not less than 5
- <object> elements have alternate text
- Select elements have associated label elements
- Skip links are focusable
- No element has a [tabindex] value greater than 0
- Tables have different content in the summary attribute and <caption>
- Touch targets have sufficient size and spacing
- Cells in a <table> element that use the [headers] attribute refer to table cells within the same table
- <th> elements and elements with [role="columnheader"/"rowheader"] have data cells they describe
- [lang] attributes have a valid value
- <video> elements contain a <track> element with [kind="captions"]
- All heading elements contain content
- Identical links have the same purpose
- Document has a main landmark
- Elements with visible text labels have matching accessible names
- Tables use <caption> instead of cells with the [colspan] attribute to indicate a caption
- <td> elements in a large <table> have one or more table headers
- Valid doctype
- Character encoding
- Accessibility grades on Project ScanGov
- ScanGov Accessibility
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