PDF to Base64 Converter

Sending PDFs through JSON APIs

JSON has no binary type, so REST APIs that receive documents usually take them as a Base64 string. E-signature platforms, invoicing and e-billing systems, print and mail services, OCR engines and document archives commonly accept PDFs this way, in a field such as content, file or documentBase64, with the file name in a separate field. Some services return PDFs the same way; Base64 to PDF turns those back into files.

Send raw Base64 without line breaks unless the API documentation says otherwise, since many APIs reject a value that still carries the data:application/pdf;base64, prefix. Keep request size limits in mind too: a 7.5 MB PDF becomes about 10 MB of Base64.

Recognizing a Base64 PDF

A PDF file begins with the characters %PDF- followed by the version number. Encoded as Base64, those bytes always give a string starting with JVBERi0. A long string starting with JVBER in an API response, a database column or a log file is almost certainly a PDF. The same check works before you send a payload: if your string starts with anything else, you may have encoded the wrong data, or encoded it twice.

Embedding a PDF in HTML

A data URI places the whole PDF inside an HTML page, with no separate file to host:

<embed src="data:application/pdf;base64,JVBERi0..." type="application/pdf" width="100%" height="600">

<iframe src="data:application/pdf;base64,JVBERi0..." width="100%" height="600"></iframe>

This works in desktop browsers with a built-in PDF viewer, but it has limits. Many mobile browsers do not display PDFs inside a page at all. Chrome and some other browsers also block a page from sending the whole tab to a data: URL, so a link or a window.open call pointing at a data:application/pdf URI may open a blank tab or do nothing. To open a PDF in a new tab from JavaScript, convert the Base64 to a Blob URL instead. For documents larger than a few megabytes, a normal file URL is usually the better choice.

Encoding a PDF in code

# Python: build a JSON request body
import base64, json
from pathlib import Path

pdf_b64 = base64.b64encode(Path('invoice.pdf').read_bytes()).decode('ascii')
body = json.dumps({'filename': 'invoice.pdf', 'content': pdf_b64})

// Browser: file comes from an <input type="file">
const reader = new FileReader();
reader.onload = () => {
  const pdfBase64 = reader.result.split(',')[1]; // drop the data URI prefix
};
reader.readAsDataURL(file);