Complete Guide to Converting PDF to Base64

Converting a PDF to Base64 turns the file's binary bytes into a plain text string made only of letters, numbers, and a few symbols. That string can travel through systems built for text — JSON payloads, XML documents, databases, and older email protocols — without the file needing its own upload slot or storage path.

This matters whenever a separate file upload is not available or not wanted: a serverless function that only accepts JSON, a webhook that posts a single request body, or a database column that stores documents as text instead of binary blobs.

Base64 maps every three bytes of the original file to four text characters, so the encoded string is always a little larger than the source PDF. For the technical detail, see how Base64 encoding works.

Encoding is reversible and lossless. The decoded bytes match the original PDF exactly, so nothing about the document's content or formatting changes — only its representation while in transit or storage.

Open PDF to Base64, choose the PDF file, and let it generate the encoded string directly in your browser. Copy the result or download it as a text file, depending on where you need to paste it next.

Test the round trip before relying on it in production: decode the string back into a PDF and confirm it opens normally. This catches copy-paste issues — like extra line breaks — before they reach a real system.

A Base64 string is roughly 33% larger than the original PDF, because every 3 bytes of input become 4 characters of output. A 300 KB PDF becomes a string close to 400 KB.

If that increase matters for your email provider, API gateway, or storage budget, plan around it. See common PDF to Base64 problems for size limits that tend to trip people up.

A raw Base64 string is the encoded bytes by themselves. A data URI wraps that string with a prefix describing the file type, which browsers and some viewers need to render it directly.

If you only need to move the file through an API or store it in a database field, the raw string is usually enough — see the Base64 vs Data URI comparison for when each format applies.

For large or frequently downloaded PDFs, a hosted file URL is often a better fit than Base64: the payload stays small, and the file can be cached or streamed instead of being copied into every request.

Base64-encoded PDFs show up most often in JSON API requests and responses — see how to use a Base64 PDF in a JSON API request — as well as in webhook payloads, database columns that store documents as text, and configuration files that embed a small certificate or report.