HTML Guides for double quotes
Learn how to identify and fix common HTML validation errors flagged by the W3C Validator — so your pages are standards-compliant and render correctly across every browser. Also check our Accessibility Guides.
This error is almost always caused by copying and pasting code from a word processor, CMS rich-text editor, blog post, or PDF. These tools often auto-correct straight quotation marks (") into typographic (curly or “smart”) quotes (" and "). While curly quotes look nicer in prose, they are not valid as attribute delimiters in HTML. The browser and the W3C validator only recognize the standard straight double quote (", U+0022) or straight single quote (', U+0027) as attribute value delimiters.
When the validator encounters markup like <meta property="og:type", the curly quotes are treated as part of the attribute’s value. The validator then sees the value as "og:type" — a string wrapped in literal curly quote characters. Since the property attribute in RDFa (which Open Graph Protocol relies on) expects a term or an absolute URL, and "og:type" is neither, the validator reports the error.
This problem can affect any HTML attribute, but it’s especially common with <meta> tags for Open Graph, Twitter Cards, and other social sharing metadata, since developers frequently copy these snippets from documentation or tutorials.
How to fix it
- Find the curly quotes. Look at the property attribute value in your source code. Curly opening quotes (", U+201C) and closing quotes (", U+201D) may look nearly identical to straight quotes in some fonts, so use your editor’s find-and-replace feature to search for " and ".
- Replace them with straight quotes. Swap every " and " with a standard straight double quote (").
- Disable smart quotes in your editor. If you’re writing HTML in a rich-text editor or word processor, turn off the “smart quotes” or “typographic quotes” feature. Better yet, use a dedicated code editor (like VS Code, Sublime Text, or similar) that won’t auto-replace quotes.
Examples
Incorrect — curly quotes around the attribute value
<meta property="og:type" content="website" />The curly " and " characters become part of the value itself, producing the validator error: Bad value "og:type" for attribute property.
Correct — straight quotes around the attribute value
<meta property="og:type" content="website" />Standard straight double quotes correctly delimit the attribute values, and the validator sees og:type as expected.
Correct — single straight quotes are also valid
<meta property='og:type' content='website' />Straight single quotes (', U+0027) work just as well as straight double quotes for delimiting HTML attribute values. Use whichever style your project prefers, but be consistent.
Full Open Graph example
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>My Page</title>
<meta property="og:title" content="My Page">
<meta property="og:type" content="website">
<meta property="og:url" content="https://example.com/">
<meta property="og:image" content="https://example.com/image.png">
</head>
<body>
<p>Hello, world!</p>
</body>
</html>All property and content attributes use straight double quotes, ensuring clean validation and correct parsing by social media crawlers.
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