How to Decode Base64 to PDF Documents in the Browser

Many backend enterprise APIs return generated PDF invoices, tickets, and contracts as Base64-encoded strings inside JSON responses (e.g. `{"pdfBase64": "JVBERi0xLjQK..."}`).

Client-Side JavaScript PDF Generator

Instead of forcing the server to host a temporary file, you can convert the string into a real PDF in the user's browser memory: ```javascript function downloadBase64Pdf(base64String, filename = "document.pdf") { // 1. Decode Base64 to binary string const byteCharacters = atob(base64String); const byteNumbers = new Uint8Array(byteCharacters.length); for (let i = 0; i < byteCharacters.length; i++) { byteNumbers[i] = byteCharacters.charCodeAt(i); } // 2. Create Blob with application/pdf MIME type const blob = new Blob([byteNumbers], { type: "application/pdf" }); // 3. Trigger immediate download const link = document.createElement("a"); link.href = URL.createObjectURL(blob); link.download = filename; link.click(); URL.revokeObjectURL(link.href); } ```

You can also paste any Base64 string directly into Toolstack's Base64 File Decoder to preview and save the file with one click.