How can you secure your website with HTML5?

2 Validate user input

User input is any data that your website receives from your visitors, such as forms, queries, comments, or uploads. User input can be a source of security vulnerabilities if it is not properly validated and sanitized. For example, malicious users can inject harmful code or commands into your website through user input, which can compromise your website's functionality, integrity, or data. To validate user input, you need to use HTML5 attributes and elements, such as type, pattern, required, maxlength, or datalist, to specify the format, length, and range of the input. You also need to use server-side validation and sanitization to filter out any unwanted or dangerous input.

3 Implement content security policy

Content security policy (CSP) is a mechanism that allows you to control what resources your website can load and execute. It helps you prevent cross-site scripting (XSS) attacks, which are one of the most common and dangerous web security threats. XSS attacks occur when malicious scripts are injected into your website and executed by your visitors' browsers, which can steal their data, hijack their sessions, or redirect them to malicious sites. To implement CSP, you need to use the <meta> tag or the HTTP header to specify the sources and types of content that your website can accept. You can also use nonce or hash attributes to allow specific inline scripts or styles.

4 Use subresource integrity

Subresource integrity (SRI) is a feature that allows you to verify the integrity of external resources that your website loads, such as scripts, stylesheets, or images. It helps you prevent integrity attacks, which are attacks that modify or replace the external resources with malicious ones. Integrity attacks can cause your website to malfunction, display incorrect content, or expose your visitors to malware. To use SRI, you need to use the integrity and crossorigin attributes on the <script> or <link> tags that load the external resources. You also need to generate and include the hash value of the resource using a tool like SRI Hash Generator.

5 Secure local storage

Local storage can be a great way to improve your website's performance, usability, and offline functionality, but it can also present some security risks. To protect your data, you should only use local storage for non-sensitive and temporary data like preferences, settings, or cache. Additionally, you should encrypt the data before storing it in local storage with secure and random keys that are stored in a safe place. It's also important to set expiration dates or time-to-live values for the data in local storage and delete it when it is no longer needed. Finally, use the same-origin policy to restrict access to the data in local storage and avoid cross-origin requests.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?