PDF Input

Drop your PDF here or click to upload

Supports PDF files up to 10MB

Base64 Output

What is PDF to Base64 Conversion?

Converting a PDF to Base64 encodes binary PDF data into a text string you can safely embed inside data URIs, JSON payloads, XML documents, or API responses. The RFC 4648 Base64 standard is the universal way to transmit binary files through text-only channels.

Modern REST APIs — documented by standards like OpenAPI / Swagger — frequently require file attachments as Base64 strings in their request bodies. E-signature platforms, invoicing APIs, and document services all use this approach.

All conversion happens in your browser using the native FileReader API — your PDF never leaves your computer.

How to Use the PDF to Base64 Converter

Follow these steps to convert PDF files to Base64. Each step uses the actual buttons and panels on this page.

Upload a PDF or Load Sample

Click the upload area or drag and drop your PDF onto the left PDF Input panel. Click Sample to load example PDF Base64. Supports files up to 10MB. Example: subscriber bill, carrier invoice, or contract.

View Base64 Output

The right Base64 Output panel shows the encoded string instantly. Output includes the full data:application/pdf;base64,... prefix — ready for HTML or API calls.

Copy or Download

Click Copy to copy to clipboard, or Download to save as .txt. Use Clear to start fresh. All conversion runs in your browser.

Common Use Cases

REST API File Upload

Many APIs — including Stripe's file API and document management services — accept PDF files as Base64-encoded strings in the request body rather than multipart form uploads.

Email Attachments (MIME)

The MIME standard (RFC 2045) encodes email attachments as Base64. Building custom SMTP integrations or email templating systems requires PDF-to-Base64 conversion.

Embedded PDF in HTML

Embed PDFs directly into HTML using a data URI: <embed src="data:application/pdf;base64,...">. Useful for offline web pages, email HTML, or sandboxed environments that block external URLs.

E-Signature & Document APIs

Services like DocuSign and Adobe Sign use Base64-encoded PDFs in their API payloads. Convert your PDF here before sending it to signing workflows.

Frequently Asked Questions

Is my PDF uploaded to your server?

No. The entire conversion runs in your browser using the FileReader API. Your PDF never leaves your device, making this safe for confidential documents.

Why is the Base64 output much larger than the PDF?

Base64 encoding adds approximately 33% overhead — every 3 bytes of binary data become 4 Base64 characters. A 1MB PDF will produce roughly 1.37MB of Base64 text. This is a known characteristic of Base64.

Does the output include the data URI prefix?

Yes. The output starts with data:application/pdf;base64, so you can use it directly as a data URI in HTML or CSS without modification.

What is the maximum file size?

The tool supports PDF files up to 10MB. Larger files may cause browser memory issues since the entire file must be held in memory during conversion. For larger files, consider command-line tools like GNU base64.

Can I convert the Base64 back to a PDF?

Yes! Use our Base64 to PDF tool to decode a Base64 string and download it as a PDF file.

Related Base64 Tools

More tools to complete your Base64 workflow:

PDF to Base64