In-line alerts

The in-line alert pattern is comprised of two elements: In-line validation messages and an error summary. The in-line validation messages appear near the input where the error occurred and explain what went wrong and how to fix it. The error summary element appears underneath the page or subsection heading, as applicable, and contains a list with links of the in-line validation messages appearing on the page. 

The error summary and in-line validation message elements should be used together in most cases. However, in situations where there is only one field on the page that requires validation, for example, a search field, an in-line validation message could be used on its own.

When to use this component

• Use in-line alerts to inform the user of problems on a form and provide direction on how to fix them 

When not to use this component 

• Do not use in-line alerts to inform the user of a problem they cannot fix, such as if the service is unavailable – Use a product alert instead 

Best practices 

Do 

• Display in-line alerts after a change in context, for example, when a user clicks a link or submits a form, launching a new page or an updated view 

• Ensure that error messages are clear, concise and easy to understand - Please see the Guidelines for Error and Validation Messaging article 

• Ensure that the error summary includes a heading that clearly conveys the purpose of the alert (for example, “Error”) 

• Use an appropriate status – Please see the Guidelines for Alerts article 

• When using the error summary, include in-page anchor links to the corresponding form controls to make it easier for users to get to the error they need to fix 

Don’t 

• Avoid prematurely displaying errors 

• Disable submit or save buttons – Allow the user to submit their values and then provide validation messages as needed 

• Use input masks – Instead use simple interactions and explain the expected format in the input label 

• Rely on colour alone to indicate an error 

• Never cover user’s input – Users should be able to edit the input field while also reviewing the error messages provided to them 

• Avoid the use of toast messages - Users often do not get a chance to fully read or understand the error message before it has disappeared 

Tips 

• Use clear questions in forms to avoid errors in the first place 

• Forgive trivial mistakes, for example, adding a space before or after a value 

• The worst error messages are those that do not exist - When users make a mistake and receive no feedback, it can lead to misunderstanding, wasted effort, and frustration 

Accessibility 

The WCAG criteria outlined in this section were chosen because they represent some of the most common failures when designing and implementing these components. For a comprehensive list, please see Web Content Accessibility Guidelines (WCAG) 2.1 (w3.org). 

1.4.3 Contrast (Minimum) 

The intent of this success criterion is to provide enough contrast between text and its background so that it can be read by people with moderately low vision (who do not use contrast-enhancing assistive technology). Text that is larger and has wider character strokes is easier to read at lower contrast. The contrast requirement for larger text is therefore lower. 

It is recommended to check colour contrast between the text and background using a contrast checking tool like the one provided by WebAIM WebAIM: Contrast Checker. 

Understanding Success Criterion 1.4.3: Contrast (Minimum) | WAI | W3C 

1.4.11 Non-text Contrast 

The intent of this success criterion is to ensure that active user interface components (i.e., controls) and meaningful graphics are distinguishable by people with moderately low vision. Low contrast controls are more difficult to perceive, and may be completely missed by people with a visual impairment. 

It is recommended to check that UI components have a contrast ratio of at least 3:1 against adjacent colours using a contrast checking tool like the one provided by WebAIM WebAIM: Contrast Checker.  

Understanding Success Criterion 1.4.11: Non-text Contrast | WAI | W3C 

4.1.3 Status Messages 

This criterion requires that, in content implemented using markup languages, status messages can be programmatically determined through role or properties such that they can be presented to the user by assistive technologies without receiving focus. 

The intent of this success criterion is to make users aware of important changes in content that are not given focus, and to do so in a way that doesn't unnecessarily interrupt their work. 

The intended beneficiaries are blind and low vision users of assistive technologies with screen reader capabilities. 

Understanding Success Criterion 4.1.3: Status Messages | WAI | W3C 

Key component features 

Telerik’s Form Validation component allows for multiple validation message display types, including none, tooltip and in-line. It is recommended to use the in-line display type. 

Blazor Form Demos - Validation | Telerik UI for Blazor 

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Figure 1 - Telerik Form Validation component showing an error summary and in-line validation messages 

Examples 

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Figure 2 – Telerik Form Validation component, with usability modifications 

Responsive design

In order to be inclusive to all users, we need to consider how our applications behave on smaller viewports. (For more information on viewports, see The viewport is the window to your site – Digital.gov.) While designing and building using responsive design principles will allow you to create an optimized layout for users accessing your application on smaller viewports, this is not the only benefit. This will also ensure you are supporting users with low vision who need to enlarge text by using the browser’s zoom function. 

To help ensure the responsiveness of your application, consider the following points when designing alerts:

• Preservation of content - Content shouldn’t be removed or changed to view an application on a smaller screen size. Don’t change or reduce the amount of text or functionality of an alert to fit a smaller screen size.

• Concise text - Keep text concise to avoid taking up larger amounts of space then necessary on smaller screen sizes.

• Consistency and visibility - The location of an in-line alert on the page shouldn’t change or be hidden when viewing on a smaller screen size. The entire alert should be visible without needing to scroll horizontally.

Resources 

Government of Canada resources 

Form validation - Working examples - Web Experience Toolkit (wet-boew.github.io)  

External resources 

Error message – GOV.UK Design System (design-system.service.gov.uk) 

Error summary – GOV.UK Design System (design-system.service.gov.uk) 

Error messaging | Ontario Design System 

Error-Message Guidelines (nngroup.com)