What Is Base64 Encoding?

Base64 is a binary-to-text encoding scheme. It represents any sequence of bytes — a PDF, an image, a font, an encryption key — using only 64 printable ASCII characters: the letters A–Z and a–z, the digits 0–9, and two extra symbols, usually + and /.

Because the output uses only common, printable characters, it can pass safely through systems that were designed to carry text rather than arbitrary binary data.

Many of the protocols and formats the web relies on — early email standards, JSON, XML, and URLs — were built around text, not raw bytes. Some of those channels strip, change, or reject certain byte values outright.

Base64 sidesteps the problem by re-expressing binary content as text first. This is the same idea behind converting a PDF to Base64: the file's bytes become a string any text field can hold.

Base64 is not encryption and not compression. It does not hide or protect data — anyone can decode it instantly — and the encoded output is always larger than the input, never smaller.

It is also not a file format. It does not know whether the bytes it represents are a PDF, a JPEG, or something else; that information has to travel alongside it, usually in a separate field or as part of a data URI.

A PDF is just a sequence of bytes like any other file, so it encodes the same way as an image or a font. For the mechanics of the conversion, see how Base64 encoding works, and for a full walkthrough see the PDF to Base64 guide.