vercel/next.js · error · Error

Failed to parse source map URL for

Error message

Failed to parse source map URL for ${filename}.

What it means

Wrapper in getSourceMapFromFile: the file's sourceMappingURL is a data: URI, but decoding it with dataUriToBuffer threw — the inline source map URL is malformed. The underlying decode error is chained as cause so the broken data URI can be diagnosed.

Solutions

1. Fix the sourceMappingURL comment in the file to a valid data URL or path.

When it happens

Trigger: The sourceMappingURL of a file cannot be parsed.

Common situations: A malformed source map URL comment in a compiled file.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of vercel/next.js@0eb3775416 (2026-08-19). Data as JSON: /api/errors/f13374ae40085320. Report an issue: GitHub.

Appendix: source

Thrown at packages/next/src/server/dev/get-source-map-from-file.ts:52

  } catch (error) {
    throw new Error(`Failed to read file contents of ${filename}.`, {
      cause: error,
    })
  }

  const sourceUrl = getSourceMapUrl(fileContents)

  if (!sourceUrl) {
    return undefined
  }

  if (sourceUrl.startsWith('data:')) {
    let buffer: dataUriToBuffer.MimeBuffer

    try {
      buffer = dataUriToBuffer(sourceUrl)
    } catch (error) {
      throw new Error(`Failed to parse source map URL for ${filename}.`, {
        cause: error,
      })
    }

    if (buffer.type !== 'application/json') {
      throw new Error(
        `Unknown source map type for ${filename}: ${buffer.typeFull}.`
      )
    }

    try {
      return JSON.parse(buffer.toString())
    } catch (error) {
      throw new Error(`Failed to parse source map for ${filename}.`, {
        cause: error,
      })
    }
  }

View on GitHub (pinned to 0eb3775416)