Base64 to PDF Converter

Copying Base64 out of an API response

Services that generate invoices, shipping labels, reports or signed contracts often return the PDF inside JSON, for example {"filename": "label.pdf", "data": "JVBERi0..."}. Copy only the text between the quotation marks after the field name, and watch for these details:

• Escaped slashes. Some JSON encoders, PHP's json_encode among them, write every / as \/. Since / is a normal Base64 character, replace \/ with / before pasting, or parse the JSON first and copy the value.
• Quotes and commas. Leave out the surrounding quotation marks and any trailing comma.
• Line breaks. Spaces and real line breaks inside the Base64, such as a value wrapped at 76 characters, are fine and do not need to be removed. Literal \n or \r\n sequences in raw JSON are a different matter: they are backslash characters and must be deleted.

Copying the value from the parsed view in your browser's developer tools avoids all of these escaping problems.

Extracting a PDF attachment from an email

Email attachments are stored as Base64 inside the raw message. Open the message source ("Show original" in Gmail, "Message Source" in Thunderbird, "Raw Source" in Apple Mail) and find the part whose headers include Content-Type: application/pdf (or application/octet-stream with a .pdf file name) and Content-Transfer-Encoding: base64. Copy the block that starts after the blank line below those headers and ends before the next line beginning with --, which is the MIME boundary. Paste it here as it is; the line breaks are ignored.

Showing a Base64 PDF in your own web app

When your front end receives a Base64 PDF and needs to display it, a Blob URL is more reliable than a data URI, which some browsers refuse to open in a new tab:

const bytes = Uint8Array.from(atob(base64), c => c.charCodeAt(0));
const blob = new Blob([bytes], { type: 'application/pdf' });
const url = URL.createObjectURL(blob);
window.open(url); // or use it as the src of an <iframe>

Call URL.revokeObjectURL(url) once the document is no longer needed to release the memory. Note that atob only accepts the standard Base64 alphabet, so convert URL-safe input (- and _) first.