URIError

URIError is thrown when a global URI handling function (encodeURI, decodeURI, encodeURIComponent, decodeURIComponent) is given a malformed URI or the string to decode contains invalid percent-encoding sequences.

Common causes

• Decoding a string with invalid percent-encoding (e.g., %ZZ)
• Encoding a string with unpaired surrogates
• Passing malformed URI strings to decodeURIComponent()
• Double-encoding or double-decoding URIs
• Handling user-provided URLs without validation

How to fix it

• Wrap decodeURIComponent() calls in try/catch
• Validate URI strings before decoding
• Use the URL constructor for parsing URLs safely
• Avoid double-encoding by checking if already encoded
• Sanitize user input before URI operations

Example

// Error example
decodeURIComponent("%ZZ");
// URIError: URI malformed

decodeURI("%E0%A4%A");
// URIError: URI malformed

// Fix with try/catch
function safeDecode(str) {
  try {
    return decodeURIComponent(str);
  } catch (e) {
    return str;  // Return original if invalid
  }
}

// Fix with URL constructor
const url = new URL("https://example.com/path?q=hello%20world");
console.log(url.searchParams.get("q"));  // "hello world"

Related errors