Base64 is a way of representing binary data — like a PDF — using only plain text characters, so it can travel safely through systems that expect text: JSON payloads, XML documents, email attachments, database columns, and API responses. FixMyPDF's Base64 to PDF decoder takes that encoded string and turns it back into a real, openable PDF file.
This tool runs entirely inside your browser. Your Base64 string is decoded locally with the browser's own atob() function and rendered with PDF.js — it is never uploaded to our servers, never written to disk on our side, and never logged. That matters, because Base64 blobs pulled from API responses and database rows routinely contain invoices, contracts, medical records, and signed documents. You can verify this yourself: open your browser's Network tab, decode a file, and you will see no upload request.
Paste your string, click Convert, and you will see a page-by-page preview of the decoded PDF before you download anything. If the preview looks right, the file is valid. If it errors, the string is malformed or truncated — see the FAQ below for how to tell the difference.
Important: paste only the encoded payload, not the full data URI. If your string begins with data:application/pdf;base64,, delete that prefix and keep everything after the comma. The prefix contains characters (:, ;, ,) that are not valid Base64, and decoding will fail if you leave it in.
Follow these simple steps to get the result you need in under a minute:
Decoding happens locally via atob() and PDF.js. No upload request is made, so sensitive documents stay on your machine.
Every page is rendered on screen first, so you can confirm the string decoded correctly before saving.
Paste, convert, download. No account, no email, and nothing stamped onto your PDF.
Ideal for checking what an API actually returned, or what is really stored in that base64 database column.
No. Paste only the encoded payload — everything after the comma. The prefix contains colons, semicolons and commas, which are not valid Base64 characters, so leaving it in will cause decoding to fail.
No. Decoding runs entirely in your browser using the built-in atob() function, and the preview is rendered locally by PDF.js. No network request carries your data. You can confirm this in your browser's developer tools under the Network tab.
Almost always one of three things: the data: prefix is still attached; the string was truncated when copied (Base64 for a PDF is long, and terminals or log viewers often cut it off); or the string is not a PDF at all. A valid Base64 PDF decodes to bytes beginning with %PDF.
A Base64-encoded PDF almost always starts with the characters JVBERi0, which is %PDF- encoded. If your string starts with something else, it is likely a different file type — an image, a ZIP, or a Word document.
There is no limit imposed by us, but there is a practical one set by your browser. Very large strings take longer to decode, and browsers cap how much data a download link can hold, so extremely large files may fail to save. For multi-megabyte documents, decoding server-side in your own code is more reliable.
Yes, exactly. Base64 is an encoding, not a compression format — decoding returns the original bytes untouched. The PDF you download is byte-for-byte the file that was encoded, with no quality loss.
Yes — use our <a href="/pdf-to-base64">PDF to Base64 converter</a> for the reverse direction.
Yes. It runs in any modern browser, including Safari on iPhone and Chrome on Android, though pasting very long strings is easier on a desktop.
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