Base64 to PDF

Base64 is an encoding scheme that converts binary data into a sequence of ASCII characters. It is widely used when binary content — like a PDF file — needs to be embedded in text-based formats such as JSON, XML, HTML, or email. When an API returns a PDF as a Base64 string, or when a document is embedded as a Data URL in a web application, you need a reliable way to decode that string back into a real PDF file. This tool does exactly that, entirely inside your browser.

What Is a Base64-Encoded PDF?

A Base64-encoded PDF is a PDF file that has been converted into a text string using the Base64 encoding algorithm. The file's binary bytes are grouped in sets of three and mapped to four printable ASCII characters from a 64-character alphabet. The resulting string is about 33% larger than the original binary file but can be safely transmitted in any text field without corruption. You will often see it in API responses, email attachments, browser storage, or data attributes in HTML elements.

Data URL vs. Raw Base64

A Data URL wraps the Base64 string in a standard format that includes the MIME type: data:application/pdf;base64, followed by the encoded content. Raw Base64 is just the encoded string with no prefix. Both formats represent the same underlying PDF file. Use the Data URL toggle when your string starts with data:, and use the Base64 Only toggle when you have just the encoded characters without a prefix. The tool strips the Data URL prefix automatically before decoding.

Common Situations Where You Need This Tool

• API responses that return PDFs as Base64: Many REST APIs, especially in document generation and e-signature services, return the final document as a Base64 string. This tool lets you decode and preview it without writing any code.
• Debugging email attachments: Email protocols encode attachments in Base64. If you are troubleshooting a corrupted attachment or want to inspect the raw content, paste the encoded block here to see the actual PDF.
• Browser storage inspection: Web applications sometimes cache PDFs in localStorage or IndexedDB as Data URLs. You can paste the stored value here to view the document without triggering a new network request.
• Testing and development: When building apps that generate or receive PDF documents, this tool gives you a fast way to validate that your encoding and decoding pipeline produces a working PDF.

How the Conversion Works

When you click Convert, the tool takes your Base64 string, strips the Data URL prefix if present, and passes it to the browser's built-in atob() function to decode it into binary data. That binary data is then wrapped in a Blob with the application/pdf MIME type. PDF.js receives the binary array buffer and renders each page onto an HTML canvas element. The download button creates an object URL from the same Blob and triggers a browser download — no server is involved at any step.