BoundaryML/baml · error · Error

Pdf is not a URL

Error message

Pdf is not a URL

What it means

BamlPdf.asUrl() only returns this.content when the PDF was constructed from a URL. If the instance holds base64 data instead, the accessor throws 'Pdf is not a URL' to prevent silently misusing base64 bytes as a URL.

Solutions

1. Check pdf.isUrl() before calling asUrl(), and fall back to asBase64() otherwise.
2. Use toBase64() or asBase64() when you need the binary content regardless of source form.
3. If a URL is required, construct the Pdf from a URL (BamlPdf.fromUrl) at the source.

Example fix

// before
const url = pdf.asUrl();
// after
if (pdf.isUrl()) { const url = pdf.asUrl(); } else { const [b64, mediaType] = pdf.asBase64(); }

function pdfHasUrl(pdf: BamlPdf): boolean { return pdf.isUrl(); }

try {
  const url = pdf.asUrl();
} catch (e) {
  if (e.message === 'Pdf is not a URL') {
    const [b64, mediaType] = pdf.asBase64();
    // handle base64 path
  } else throw e;
}

When it happens

Trigger: Calling pdf.asUrl() on a BamlPdf created via BamlPdf.fromBase64(...) (type !== 'url'), i.e. whenever isUrl() returns false.

Common situations: Receiving a BamlPdf from a function result or user upload that is base64-encoded and blindly calling asUrl(); assuming all Pdf objects carry a remote URL.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

• Pdf is not base64
• Audio is not a URL
• Audio is not base64
• BAML internal error (AWSBedrock): Pdf file should have been…
• Could not determine mime type for PDF input. Only…

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/0efafaf074859f0d. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_typescript/pdf.js:68

     */
    static async fromUrlAsync(url) {
        const response = await fetch(url);
        const blob = await response.blob();
        return BamlPdf.fromBlob(blob);
    }
    /**
     * Check if the pdf is stored as a URL
     */
    isUrl() {
        return this.type === "url";
    }
    /**
     * Get the URL of the pdf if it's stored as a URL
     * @throws Error if the pdf is not stored as a URL
     */
    asUrl() {
        if (!this.isUrl()) {
            throw new Error("Pdf is not a URL");
        }
        return this.content;
    }
    /**
     * Get the base64 data and media type if the pdf is stored as base64
     * @returns [base64Data, mediaType]
     * @throws Error if the pdf is not stored as base64
     */
    asBase64() {
        if (this.type !== "base64") {
            throw new Error("Pdf is not base64");
        }
        return [this.content, this.mediaType || ""];
    }
    /**
     * Convert the pdf to a JSON representation
     */
    toJSON() {

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