Full URL to the JavaScript file
Subresource Integrity hash (sha256-, sha384-, sha512-)
Ready to generate
Fill in the fields and click Generate// generate script tags with async, defer, sri, and crossorigin
Generate HTML script tags with async, defer, type=module, integrity (SRI), and crossorigin settings. Copy production-ready script tags instantly.
Ready to generate
Fill in the fields and click GeneratePaste the full CDN or local path to your JavaScript file.
Choose loading strategy, type, integrity hash, crossorigin, and extra attributes.
Click Generate, then copy the ready-to-use script tag directly into your HTML.
The HTML Script Tag Builder generates production-ready <script> tags with the correct combination of attributes for security, performance, and compatibility. Configure SRI integrity, async/defer loading, ES modules, and crossorigin policies in seconds.
async downloads the script in parallel with HTML parsing and executes it as soon as it's downloaded, potentially interrupting parsing. defer also downloads in parallel but waits until the HTML is fully parsed before executing — making it safer for DOM-dependent scripts.
Use type="module" when your script uses ES module syntax (import/export). Module scripts are deferred by default, always run in strict mode, and have their own scope. Add a nomodule fallback script for older browsers that don't support ES modules.
Subresource Integrity (SRI) is a security feature that lets browsers verify that a CDN-hosted file hasn't been tampered with. You provide a cryptographic hash (sha384 recommended) of the expected file content. If the file doesn't match, the browser refuses to execute it.
crossorigin="anonymous" sends a CORS request without credentials (no cookies). It's required when using SRI with cross-origin scripts. use-credentials sends credentials with the CORS request — use this only if the server is configured to handle credentialed requests.
The fetchpriority attribute hints to the browser how to prioritize downloading this resource relative to others. high is useful for critical scripts needed early in page load. It's supported in modern browsers and safely ignored by older ones.
A CSP (Content Security Policy) nonce is a random token your server generates per page request. Including it in your script tags allows those scripts to run when you have a strict CSP that otherwise blocks inline scripts or external scripts. This tool adds a placeholder you replace server-side.
The HTML Script Tag Builder is a free browser-based tool that helps developers generate correct, secure, and performance-optimized <script> tags for their HTML pages. Whether you're loading a third-party CDN library, an ES module, or a critical performance-sensitive script, this tool ensures you configure every attribute correctly without memorizing syntax.
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The <script> element is one of the most frequently used HTML tags, yet its attributes are often misunderstood or misconfigured. Using the wrong loading strategy or omitting security attributes can lead to performance regressions, security vulnerabilities, or broken functionality in some browsers.
When a browser encounters a <script> tag during HTML parsing, the default behavior is to stop parsing, download the script, execute it, and then resume parsing. This "render-blocking" behavior can significantly delay page display — especially for large scripts or slow network connections.
DOMContentLoaded event. This is the safest and most recommended option for most scripts that need access to the DOM.When you load scripts from a CDN, you're trusting that CDN provider. If the CDN is compromised, an attacker could inject malicious code into your users' browsers. Subresource Integrity (SRI) protects against this by letting you specify the expected cryptographic hash of the script file.
The browser computes the hash of the downloaded file and compares it to the value in your integrity attribute. If they don't match — indicating the file was modified — the browser refuses to execute the script. The sha384 algorithm is recommended for most use cases as it provides a good balance of security and hash length.
Important: SRI requires you to also set a crossorigin attribute when the script is served from a different origin. Without it, the browser cannot read the response to compute the hash.
Modern JavaScript uses the ES module system with import and export statements. To tell the browser to treat a script as an ES module, you add type="module". Module scripts behave differently from classic scripts in several ways:
defer explicitlyawaitFor browsers that don't support ES modules, you can provide a fallback using the nomodule attribute. Modern browsers ignore nomodule scripts, while old browsers that don't understand modules will run them.
The crossorigin attribute controls how the browser handles cross-origin requests for the resource:
Access-Control-Allow-Credentials: true and a specific origin (not wildcard).The fetchpriority attribute is a relatively new addition that provides resource loading hints to the browser. Setting fetchpriority="high" on a critical script tells the browser to prioritize its download over other resources of the same type. This is useful for scripts that are needed early in the page lifecycle. Since unsupporting browsers safely ignore this attribute, there's no downside to including it where appropriate.
A Content Security Policy (CSP) is an HTTP response header that controls which scripts are allowed to execute on your page. Strict CSPs can significantly improve XSS (Cross-Site Scripting) resistance. A CSP nonce is a random base64-encoded value your server generates for each page request. By including this nonce in both your CSP header and your script tags (nonce="..."), you allowlist specific scripts while blocking others. This tool adds a nonce placeholder you replace server-side with the dynamically generated value.
<body> or use defer to avoid render-blockingcrossorigin="anonymous"defer over async for most scripts that need the DOMtype="module" for modern codebases with ES module support