Base64 & PDF Converter
Convert Base64 strings to PDF files and PDF files to Base64 in one focused tool. Decode a Base64 string into a downloadable PDF, or encode any PDF into a Base64 data URI. Large files supported, runs 100% in your browser.
What is Base64, and why convert PDFs?
Base64 is a text encoding that represents any binary data, the raw bytes of a PDF, an image, a video, using only 64 printable ASCII characters: the letters A–Z and a–z, the digits 0–9, and the symbols + and /. An optional = sign is used for padding. The result is roughly 33 % larger than the original binary, but it can be safely placed inside JSON, XML, HTML, email, URLs, and any other text-only channel.
A PDF file is a binary container of fonts, images, vector instructions, and metadata. Most systems are happy to read it from disk, but many integrations, REST APIs, HTML data URIs, ESign callbacks, queue messages, log payloads, can only carry text. Encoding the PDF in Base64 makes the document trivially embeddable, while decoding the string reproduces the exact same bytes, byte for byte.
This tool runs the entire encoding and decoding pipeline locally in your browser, using the standard FileReader, Blob and atob / btoa APIs. Nothing is uploaded, nothing is logged, and your documents never leave the device, ideal for sensitive contracts, invoices, medical reports, and other confidential PDFs.
Everything you need for Base64 ↔ PDF work
A single, distraction-free tool for developers, QA engineers, and ordinary users who occasionally need to inline a PDF or rescue a Base64 blob from a JSON response. Both directions, real previews, large file support.
Both directions
Decode Base64 to PDF with instant PDF preview and download, or simply encode any PDF to Base64, in the same page. Switch with a single tab click, an all-in-one Base64 PDF tool.
100% private
All processing happens locally with JavaScript, FileReader and Blob APIs. Your PDFs and Base64 strings never leave your device, no servers, no accounts, no tracking.
Large file support
Built on the browser's native streaming FileReader, the tool comfortably handles multi-megabyte PDFs, contracts, scans, manuals, ebooks, without freezing the page.
Inline PDF preview
After decoding, the resulting PDF document is also rendered in an embedded viewer container so you can easily verify the PDF file is correct before downloading it.
Smart cleanup
Strips quotes, escape backslashes, whitespace and the data:application/pdf;base64, prefix automatically, so messy strings from JSON output or logs just work.
Mobile-friendly
Responsive layout works on phones, tablets, and desktops, convert PDFs on the go with no install required. All that you need is just a modern web brwoser like Chrome or Firefox.
From string to PDF (and back) in three steps
Whichever direction you need, the workflow is short: pick the tab, drop in your input, hit convert. No signup, no install, no learning curve.
Pick a direction
Choose Base64 to PDF to decode a base64-encoded string, or PDF to Base64 to encode a PDF file. Each tab keeps its own input.
Provide your input
Paste a Base64 string (raw or data URI), or select a PDF document from your device. Drag & drop is supported for PDF files.
Convert & download
Hit Convert button, preview the result, and download the PDF or copy / export the Base64 string to a .txt file with a single click.
Who uses a Base64 PDF converter?
Encoding and decoding PDFs to Base64 sits at the heart of modern web, API and e-signature workflows. Here are some of the most common use cases.
- API developers embedding PDFs in JSON request and response bodies
- E-signature integrations (DocuSign, Adobe Sign, HelloSign webhooks)
- Web frontends rendering PDFs via
<iframe>or<embed>data URIs - Email and SMTP services inlining PDF attachments in MIME multipart
- QA & testing reproducing edge-case payloads from logs and test fixtures
- Serverless & queues passing PDFs through SQS, Lambda, Pub/Sub
- Security researchers inspecting Base64 attachments from incidents
- Database storage of small PDFs in TEXT or VARCHAR columns
What a real Base64 PDF looks like
Every PDF file begins with the magic header %PDF-. After Base64 encoding, that header always becomes one of the prefixes below.
| PDF version | Raw header bytes | Base64 prefix |
|---|---|---|
| PDF 1.3 | %PDF-1.3 | JVBERi0xLjM |
| PDF 1.4 | %PDF-1.4 | JVBERi0xLjQ |
| PDF 1.5 | %PDF-1.5 | JVBERi0xLjU |
| PDF 1.6 | %PDF-1.6 | JVBERi0xLjY |
| PDF 1.7 | %PDF-1.7 | JVBERi0xLjc |
| PDF 2.0 | %PDF-2.0 | JVBERi0yLjA |
| Data URI form | (any PDF) | data:application/pdf;base64,JVBERi0... |
Frequently asked questions
Quick answers to the questions we hear most often about Base64 encoding, PDF data URIs, and how this tool handles your files.
Base64 is a text encoding that represents binary data, like the bytes of a PDF file, using only 64 printable ASCII characters: A–Z, a–z, 0–9, + and /. Encoding a PDF in Base64 makes it safe to embed inside JSON payloads, HTML data URIs, XML documents, email messages, or anywhere only text is allowed. The trade-off is roughly a ~33% size increase versus the original raw binary.
Open the Base64 to PDF tab, paste the Base64 string into the textarea, then click Convert to PDF. The decoded document is previewed inline and a Download PDF button appears. The tool accepts both raw Base64 and full data URIs prefixed with data:application/pdf;base64,.
Switch to the PDF to Base64 tab, click the upload area or drag a PDF onto it, then click Convert to Base64. The encoded string appears in a textarea, and you can toggle whether to include the data:application/pdf;base64, prefix. Copy or export the result as a .txt file.
Yes. All encoding and decoding happens locally with the browser's FileReader, Blob, atob and btoa APIs. Your PDFs and Base64 strings never reach our servers and are not logged or stored anywhere. You can disconnect from the internet after loading the page and the converter will still work.
Yes. The tool uses the native FileReader and Blob APIs, which can handle multi-megabyte PDFs comfortably. The practical limit depends on your browser and available memory, but files of tens of megabytes are routinely supported. For extremely large PDFs (hundreds of MB), expect the conversion to take a few seconds and your browser tab to use additional memory.
A valid Base64 string contains only A–Z, a–z, 0–9, +, / and = padding, and its length is a multiple of 4. The tool automatically strips quotes, backslashes, whitespace and the data:application/pdf;base64, prefix. If your input is still rejected, check for non-Base64 characters from a different encoding (URL-safe Base64 uses - and _ instead of + and /) or for missing padding.
Yes, the converter is completely free and requires no sign-up, no email, and no payment.
A data URI is a URL that carries its content inline rather than pointing to a remote resource. For a PDF, the full data URI looks like data:application/pdf;base64,JVBERi0xLjcK…. Browsers can use it directly as an <iframe>, <embed> or anchor href to display the PDF with no separate hosting.