Puppeteer: Stylesheet URL is undefined (styleSheetId={value})

CSS coverage has a stylesheet ID without its recorded URL.

Error message

Stylesheet URL is undefined (styleSheetId={value})

{value} is replaced by the value shown in your error message.

How this error happens

CSS coverage recorded a stylesheet ID without the corresponding URL. A stylesheet’s lifecycle and the coverage collector’s records are out of sync.

The snippets use an open Chrome/CDP page named page.

await page.coverage.startCSSCoverage();

await page.setContent(
    "<style>p { color: red; }</style><p>Hello</p>"
);

const coverage = await page.coverage.stopCSSCoverage();

How to fix

Start CSS coverage before the page work you want to measure, stop it once after that work, and keep the page alive until collection finishes.

await page.coverage.startCSSCoverage();

try {
    await page.setContent(
        "<style>p { color: red; }</style><p>Hello</p>"
    );
} finally {
    const coverage = await page.coverage.stopCSSCoverage();

    console.log(coverage);
}

Things to keep in mind

This valid workflow only produces the error if stylesheet events or collector bookkeeping become inconsistent. A controlled inline stylesheet helps isolate dynamic replacement or navigation from a browser/Puppeteer issue. Do not patch private stylesheet records.

All Puppeteer errors