Code

Properly defines charset

Verifies the presence and validity of the charset declaration, as it is crucial for ensuring proper text encoding and display across various browsers and devices.

Servers and browsers communicate with each other by sending bytes of data over the internet. If the server doesn't specify which character encoding format it's using when it sends an HTML file, the browser won't know what character each byte represents. The character encoding declaration specification solves this problem.

Theoretically, a late <meta charset> element (one that is not fully contained in the first 1024 bytes of the document) can also significantly affect load performance. See Issue #10023.

How the audit works

Sitefig flags pages that do not specify their character encoding:

Lighthouse considers the character encoding to be declared if it finds any of the following:

A <meta charset> element in the <head> of the document that is completely contained in the first 1024 bytes of the document
A Content-Type HTTP response header with a charset directive that matches a valid IANA name
A byte-order mark (BOM)

Fixing the problem

Add a <meta charset> element to your HTML

Add a <meta charset> element within the first 1024 bytes of your HTML document. The element must be fully contained within the first 1024 bytes. The best practice is to make the <meta charset> element the first element in the <head> of your document.

<!DOCTYPE html>
<html lang="en">
  <head>
 <meta charset="UTF-8">
 …

Add a `Content-Type` HTTP response header

Configure your server to add a Content-Type HTTP response header that includes a charset directive.

Content-Type: text/html; charset=UTF-8

How the audit works

Fixing the problem

Add a Content-Type HTTP response header

Add a `Content-Type` HTTP response header